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Lung function in teenage Bangladeshi boys and girls
Resph'atory Medicine (1990) 84, 47-55
Lung function in teenage Bangladeshi boys and girls M.A. RAHMAN,M.B. ULLAH* and A. BEGUMt
Department of Physiology and Pharmacology, Medical School, Queen'sMedical Centre, Universityof Nottingham, Nottingham NG7 2UH, U.K. Data on forced vital capacity, forced expiratory volume in one second and peak expiratory flow rate were obtained in a group of 588 healthy and well-nourished (but not obese) Bangladeshi teenagers to establish normal values in this population. Bangladeshi girls in their early teens showed higher peak expiratory flow rates than boys of the same age but while this continued to rise in boys after the age of 15 years the peak expiratory flow rate in girls seemed to have attained its maximum values by that age. Correlations between sitting height and the lung function variables were found to be marginally greater than those with standing height. Prediction equations were calculated for each lung function variable with sitting and standing separately. Comparison of the results in our study with those reported from other ethnic groups indicate that Bangladeshi values are lower than those of Europeans, Jordanians or Chinese but not significantly different from those reported for Libyans. Since in practice, genetic, nutritional and environmental factors are not readily disentangled, norms for a given study population need to be derived from healthy subjects of similar background and ethnicity.
Introduction Lung function measurements are important aids to diagnosis and are also important guides to therapy in patients with respiratory diseases. Standard values of lung function indices for Europeans of all ages have been established (1-3). Considerable work has been done on Afro-Carribean subjects (4-6), and on children (7-9) and adults of Indian (10-12) or Pakistani origin (13-15). Very little is known, however, about lung function values in teenagers of the Indian subcontinent although teenagers constitute a substantial proportion of the population in Bangladesh and India. There is only one study, by Bhattacharya and Bannerjee (16), that reports data from Indian teenage boys and girls, Workers involved with the earliest lung function surveys in the Indian subcontinent emphasized the need for standardization of lung function indices on the basis of ethnicity and environment (17). Sobol (18) commented that every laboratory should have its own standard lung function values. Williams (14) stressed that standard values for a geographical population should be derived from a sample specific to that area. The need for information about lung function in healthy subjects from homogeneous populations Received 24 April 1989 and accepted 27 September 1989 *Current address: Jhenaidah Cadet College, Jhenaidah, Bangladesh. tCurrent address: Maeleod Road, Kotchandpur 7330, Jhenaidah, Bangladesh.
0954-6111/90/010047+ 09 $03.00/0
within a community between the ages 15 and 30 has been publicized (19), and in a recent review on spirometry (20) the comment was made that 'few data are available for several race and age groups'. In addition, with better understanding of respiratory mechanics, and with constant refinement of instruments and changing techniques, it is desirable that periodic assessments &normal values of lung function are carried out with a view to establishing more dependable and accurate data, especially in a field where few data are available. The present study was undertaken to establish, in Bangladeshi teenage boys and girls, standard values for the most commonly measured lung function variables, namely, forced vital capacity (FVC), forced expiratory volume in one second (FEV 0, [FEVJFVC]100 (FEV1%), and peak expiratory flow rate (PEFR) using a portable electronic spirometer.
Methods LOCATIONAND SUBJECTS The study was carried out at Jhenaidah Cadet College and Mymensing Girls' Cadet College (100 miles southeast and 60 miles north of Dhaka, respectively, and both at sea level). Measurements were made at a temperature of 27-31~ and a humidity of 87-93% from mid July to early September, during normal working hours, To obtain a uniform sample for reference values, a selected group of healthy 9 1990Bailli~reTindal]
48
M . A. R a h m a n et al.
Bengalee boys and girls (total of 588 subjects; 298 boys and 290 girls), aged between 12 and 19 years from these residential colleges were chosen for study. Children enter the colleges at the age of 12-13 years and stay there f o r the next 6 years. They have similar diet and training. H o u r long morning physical exercise and afternoon games and sports are mandatory for all. Height, weight and general health (including menstrual status in girls) are recorded at the begining and end of every term. Before the measurements were made, the governing body o f the Cadet Colleges was approached for permission to carry out the survey. (It was agreed that girls would be asked no questions regarding their pubertal status. However, we were allowed to use the existing records confidentially for our survey). Pubertal status for the boys was not defined. Prospective subjects were asked to answer questions set according to the I987 recommendation by the American Thoracic Society. Screening was carried out by medical officers of the respective colleges to exclude those with c o m m o n cold or other respiratory diseases, Those with a history of food allergy were included as long as they showed no respiratory signs or symptoms at the time of study. A lecture was given describing the whole procedure, making the children familiar with the instrument and techniques to be used during the survey. They were then given disposable cardboard mouthpieces for practice.
INSTRUMENTS
A 'pocket monitor' (Micro Medical Instruments, PO Box 6, Rochester, Kent, U.K.) was used for spirometry, It consists of a transducer head assembly connected by a length of cable to a battery-powered microprocessor control unit. This unit converts the electrical pulses generated by a turbine in t[ae transducer head into FVC, FEV~, and PEFR measurements on a digital display. The instrument was chosen after considering a report of its feasibility for epidemiological surveys by Melia et al. (22). Although the accuracy of similar instruments has been described by Chowienczyk and Lawson (23) and Gunawardena et al. (24), before carrying out the present survey the instrument to be used was calibrated in Nottingham by connecting it in series with an Ohio spirometer (Ohio Inc. Houston, Texas) in the lung function laboratory. The accuracy of FVC, FEV~ and PEFR measurements with the pocket monitor were found to be within __+3% of the standard spirometer values with Euopean as well as with Asian subjects. During the survey, after every 20 subjects tested, the monitor was calibrated with a 21 syringe which was discharged smoothly and evenly. The pocket monitor read 1.051 when 11 of air was discharged and 2. l 1 when 21 were discharged from the syringe. The readings were adjusted accordingly in the analysis of results. (No changes were observed in calibration with repeated measurements throughout the survey.
ANTHROPOMETRIC MEASUREMENTS
Age was calculated from the recorded date of birth for each b o y and girl. Subjects in the age range 12 years to 12 years 11 months were grouped in age group 12, those f r o m 13 years to 13 years 11 months in age group 13, and so on. Body weight was measured to the nearest 0.25 kg, with subjects wearing similar clothes, using a calibrated weighing machine (Krups, Ireland). Standing height was measured to the nearest 0.25 cm using a staxtiometer (21) with subjects in bare feet. Sitting height was taken with the subjects seated with the vertex maximally extended position on a flat w o o d e n chair, looking straight ahead with their knees flexed to a right angle. All the measurements were taken within 2 weeks before the lung function measurements b y the respective medical officers and three paramedical staff in each college accustomed to the routine performance of these measurements (six times per year f o r each pupil), For the present purposes, they were asked to follow strictly the IBP guidelines (21). There were few discrepancies from the routine measurements taken within the previous month,
PROCEDURE Although several people were involved in the anthropometry, the ventilatory measurements were all supervised by the same person (AR) to minimize interobserver variation as shown by Fairbairn et aL (25). The measurements were taken with the subjects in a standing position (26); nose clips were not used. Subjects were asked to breathe in fully and unhurriedly, then to close the lips round the mouthpiece and blow out as hard and as fast as they could without any pause. They were verbally encouraged during the procedure to squeeze out all air. It was ensured that belts were loosened, no pursing of the lips occurred and that subjects did not obstruct the mouthpiece with the tongue. At least 30 s was allowed between each blow. To achieve acceptable reliability of measurement according to the 1987 ATS guidelines, subjects were asked to deliver at least three but not more than eight blows until the best FVC values differed by 0'151 or less. Eighteen subjects (16 girls and two boys) were unable to achieve this by the eighth blow and were excluded. In fact, apart from these excluded subjects, data from
Lung function in Bangladeshi teenagers 49 four o r five blows were recorded for each subject, The largest FVC and FEV~ were noted even if the two values came from separate blows (20). The largest values of the FEVI/FVC% for each of the recorded blows were also noted.
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1.6 STATISTICAL
ANALYSIS
Data from the blows having the best three FVC values were considered for analysis (20) using a stepwise regression method. Sex was used as a main factor with age, weight, and standing height and/or sitting height as covariates. Since logarithmic transformation did not diminish any of the residual variances, we performed multiple linear regression analysis of the ventilatory variables on age, weight, standing height and sitting height as untransformed covariates. Prediction equations were calculated for each lung function variable with sitting height and standing height separately. Results ANTHROPOMETRIC
RESULTS
The data on five different anthropometric variables are presented in Tables 1 and also in Tables 2 and 3. The least height in both boys [1.40m (mean 1.50 -t-0.06)] and girls [1.37 m (mean 1.49 _+0.06)] were observed at age 12, and the greatest height at age 19 in boys [1'79 m (mean 1.69 +__0.04)) and 18 in girls [1'68 m (mean 1.57_+0.04)]. The mean increase in height in girls between age 12-15 years was 6cm while that between 15-18 years was 1 cm. On the other hand, boys showed an almost steady growth from 12 through to 19 years (Table 2). The mean height observed at different ages in boys and girls are shown in Fig. 1. Nineteen girls from the age range 12 (42% of the sample group age 12) and two girls from age range 13 had not reached their menarche at the time of survey, according to the records in the college. It should also be noted that the college selection process would have excluded overweight subjects. The range of BMI (kg m -z) in this population was boys 13.3 to 26.8, girls 13.7 to 23.8 (Table 1). It was not therefore, possible to consider effects of obesity in this study. FVC ANDFEV~ The values of different lung function variables are presented according to age (Table 2) as well as according to height (Table 3). FVC and FEVI increased steadily in boys throughout the age range. In the girls, both levelled off at about 15 years of age (Table 2). The ventilatory function values in premenarcheal girls were similar to those of the rest of the age group. The matrix in Table 4 shows significant positive cor-
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Fig. 1 Comparison of height in Bangladeshi teenage boys (I-1) and girls (I1~).Measurements are defined as mean with one standard deviation. (SD shown by bars). relations of FVC and FEVi, with all four anthropometric variables in both sexes. Correlation of FVC and FEV~ with sitting height was marginally better than standing height followed by age and weight, respectively. On this basis separate prediction equation were derived with sitting or standing height as covariates. Although in all cases weight showed significant correlation (Table 4), it contributed little that was not covered better by the other variables and was therefore eliminated in the step-wise regression analysis (summarized in Table 5). FEV1% AND PEFR Highest values of FEVI % from the accepted blows for each subject were recorded (Table 5). These were not different from the FEV~% derived from the separate highest FEV 1 and FVC values (boys:mean 88.6%, SD2' 1; girls:mean 86'5%, SD2"3). FEV 1% did not show a significant correlation with any of the anthropometric variables either in boys or in girls. No regression equation is therefore presented. PEFR resembled FVC and FEVa in its correlations with the anthropometric variables, except in that weight was a significant factor (Table 4). The correlation value, r, for PEFR and age was more in boys (0.76) than in girls (0'50). This r-value increased (0.59) in girls when only age range 12-15 years was considered. Weight was retained in the equation even at the cost of height or sitting height when analysed by step-wise regression method (see Table 5). Though the effects of standing and sitting heights were closely similar in both sexes, standing height was a marginally better predictor in girls, and sitting height in boys. Discussion
Although some measurements of lung function carried out in the Indian population have included
50
M. A, Rahman et al. Table 1 Anthropometric data of Bangladeshi healthy teenagers
Boys (n =296)
Girls (n = 274)
Mean (SD)
Range
Mean (SD)
Range
15.5 (2,0) 47-1 (8-9) 1.62 (0.1) 0,83 (0,05) 51.3 (1'0) 17,9 (2,2)
12.0-19.0 25.0-73.0 1.37-1.79 0.69-0.94 49.0-54.0 13.3-26,8
14.11 (2'0) 44.0 (5.9) 1"54 (0,5) 0.77 (0,02) 50,3 (0.06) 18.4 (2.0)
12,0-18.9 27'7-61,0 1,40-1.68 0.71--0,85 48,8-52.1 13.7-23.8
Age in years Weight (kg) Standing height (m) Sitting height (m) Sitting: Standing height (%) Weight for height (kgm -2)
Table 2 Data in relation to age in Bangladeshi boys and girls
Age (years) 12 13 14 15 16 17 18 19 Total
Sex
No.
Ht (m)a
Sht (m)b
Wt (kg)c
FVC (1)d
FEV~ (1)~
FEVJ FVC%
PEFR (1 min-~)
Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Boys Girls
46 45 40 53 26 40 37 41 46 18 45 45 54 36 2 296 278
1,49(0.009) 1.50(0.006) 1'56(0.007) 1.52(0.006) 1-60(0,007) 1,54(0.007) 1-62(0.007) 1.56(0,006) 1,66(0.006) 1-57(0.012) 1.67(0.007) 1.58(0,007) 1.69(0,006) 1.57(0,007) 1.75(0.000) 1.62(0.005) 1.54(0.003)
0.75(0.005) 0"75(0.003) 0"79(0.004) 0,76 (0.003) 0"81(0.004) 0.77(0,004) 0"83(0.004) 0"79(0,003) 0,86(0.004) 0.79(0-006) 0,87(0,004) 0,79 (0.003) 0.88 (0.003) 0.79 (0,004) 0,92(0.005) 0.83 (0,003) 0,78 (0.002)
34.9(0.83) 39,3(0,77) 42.0(0.80) 40.6(0.69) 42,8(0.92) 44.3(0,70) 47,0(0.99) 46.8(0.74) 50.9(0,74) 45'9(1.31) 52.8(i,00) 46'9 (0.76) 55'1(0.85) 47.2(0,89) 56'3(2.75) 47'I (0,52) 44,1 (0.35)
2,03(0,047) 1.92(0.034) 2.42(0,041) 2,04(0.032) 2.60(0"045) 2,14(0.038) 2.78(0.028) 2,33(0.035) 2.97(0.031) 2.39(0"058) 3,06(0,048) 2.47(0,037) 3,19(0,048) 2'38 (0.043) 3,67(0.175) 2.75(0'028) 2.21(0,019)
1.79(0.043) 1.64(0,029) 2,13 (0.038) 1.76(0,029) 2.30 (0.040) 1'83(0'032) 2.45(0.025) 2.02(0.034) 2.65(0,029) 2.08 (0'052) 2,73 (0.045) 2.17(0'035) 2.84(0,044) 2.08 (0,037) 3.28(0,135) 2.44(0,026) 1.92(0.017)
88,5 (0.26) 86,9(0,3l) 89,0 (0.25) 87.6(0,26) 89,2 (0.33) 87.7 (0.25) 89,1(0,22) 87,6 (0,36) 89,5 (0.24) 88,8 (0'37) 90,0(0'26) 88.6(0,33) 89,4(0,21) 88,8 (0,24) 89,6(0,58) 89,2(0,09) 87,9 (0,12)
312 (7"3) 354(3'9) 349 (7"3) 371 (3,7) 372 (9'5) 385 (4.7) 410(9,9) 400(4,1) 447 (8,4) 395(7,7) 466 (8.2) 397 (4,0) 487 (8,3) 402 (5,5) 518(5.0) 412 (4.8) 384(2,0)
~Ht(m)= standing height in metres bSht(m)= sitting height in metres CWt(kg)= weight in kg aFVC = forced vital capacity in litres 'FEV~= forced expiratory volume in litres in 1 s rPEFR =peak expiratory flow rate in litres per min Values are mean (standard error): all volumes are in BTPS. Bengalees (17,27,28), no systematic study has been carried out in the Bangladeshi population, The present study was therefore undertaken to establish a reference standard for a teenage population of Bangladesh. The results of this study indicate that in Bangladeshi teenage boys and girls the forced expiratory volumes increase with age, Bangladeshi girls have a lower FVC compared to those of boys of similar age, weight, height or sitting height, except during the early teens when both boys and girls show similar values. Such differences also existed in FEV~ in boys and girls of the same age and the differences remained even when heights were taken into account. These findings are not
in agreement with the observation that differences in FEV l in children between sexes disappear if height is taken into account (29). Bangladeshi girls in their early teens showed higher P E F R than boys of the same age, as has previously been reported for children of European descent (30, 31). However, while P E F R continued to rise in boys after the age of 15 years, P E F R in girls seemed to have attained its maximum values by that age. There were no differences between the mean of the highest values of FEV 1% from the accepted blows for each subject and the FEV~ % derived from the separate highest FEV~ and FVC values. This is not unexpected since the selection criteria for the acceptable blows were
Lung function in Bangladeshi teenagers
51
Table 3 Data in relations to heights in Bangladeshi boys and girls Ht(m)~
No.
Sex
Age(years)
Sht(m)b
Wt(kg)~
FVC(1)d
FEV,(1) c
FEV1%
PEFR (Ira-t )
!.37-1,39 1.40-1.44
5 6 4 21 43 19 102 54 83 68 37 77 9 35 11
Boys Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Boys
12.2(0.11) 12.4 (0.1 I) 12.0(0.00) 12.7 (0.06) 13.1 (0.17) 13'1 (0.16) 14'6(0'20) 14.2(0.19) 15.6(0.19) 15.6 (0.20) 16.0(0.25) 16.7(0,13) 17.1(0.36) 17.4 (0.16) 18,2(0.24)
0,70(0.005) 0.72(0.004) 0'71(0'002) 0.75(0.003) 0.74(0.001) 0.77(0.002) 0.77(0'001) 0.80(0.002) 0,79(0.001) 0,83(0.003) 0.81(0,002) 0,86(0,002) 0.83(0.01I) 0.89(0'003) 0.91(0.004)
27.8(1.3) 30.6(0.9) 34.6(3.8) 35.6(1.2) 38'0(0.7) 36.8(0.5) 43.1(0.4) 42.4(0.7) 45.9(0.5) 48.5 (0"7) 48.2(5.5) 51.8(0.7) 53.2(0.8) 55.9(0.9) 58.6(1.9)
1.58(0.08) 1.68(0.06) 1.53(0.04) 2.03(0.04) 1.82(0,02) 2.19(0.05) 2.11(0.02) 2'58(0'03) 2.36(0.02) 2'80 (0.03) 2.60(0'03) 2,98(0.02) 2.80(0.06) 3.22(0'05) 3.74(0,14)
1.39(0,08) 1.45 (0.05) 1.31 (0.05) 1.78 (0.04) 1.56(0.02) 1.93 (0.04) 1.83 (0.02) 2.28(0.03) 2.04(0.02) 2.48 (0.02) 2,21(0.03) 2.65(0,02) 2.49(0.06) 2.88 (0.05) 3.36(0.12)
88(0.7) 86 (1.2) 85(1"7) 88 (0.4) 86(0.4) 88(0'3) 87(0'2) 88(0'2) 86(0.2) 88 (0,2) 87(0'3) 89(0.2) 89(0.6) 89 (0.3) 89(0.4)
281(19.7) 264 (17.2) 306 (5"4) 315 (11.0) 349 (3.2) 321 (9.0) 377 (2.1) 370 (7'4) 394 (2.4) 423 (8.0) 414 (3.8) 450 (5.6) 450(13.2) 498 (10'6) 508(15.9)
1.45-1.49 1.50-l.54 1.55-1.59 1.60-1,64 1.65-1,69 1.70-1.74 1,75-1.79
.'Ht(m) = standing height in metres ~Sht(m) = sitting height in metres 'Wt(kg) = weight in kg dFVC = forced vital capacity in litres ~FEV~--forced expiratory volume in litres in 1 s rPEFR = peak expiratory flow rate in litres per min Values are mean (standard error), all volumes are in BTPS
Table 4 Simple correlation coefficients between lung function measurements and different anthropometric variables in healthy Bangladeshi teenage boys and girls Age (years) Age (years) Ht(m) Sitting Ht(m) Wt(kg) FVC(1) FEV~(1) FEVt% PEFR(I m-~)
Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls
Ht(m)~ Sht(m)~ Wt(kg)c FVC(1)~
FEVf(1)~
FEV~% PEFR(lm-t)r
1.00 1.00
0.81 0'54 0.84 0.56 0.77 0.50 0,82 0,63 0.82 0.65 0.20 0.23 0,76 0,50
1'00 1'00 0.96 0.95 0.82 0.63 0.90 0.87 0.88 0.83 0.20 0.09 0'76 0'75
~Ht(m) = standing height in metres bSht(m) -sitting height in metres ~Wt(kg)---weight in kg aFVC = forced vital capacity in litres ~ = forced expiratory volume in litres in 1 s rPEFR = peak expiratory flow rate in litres per rain
1.00 1.00 0.83 0.63 0.90 0.91 0.89 0.88 0.21 0.09 0.80 0.73
1'00
1'00 0'78 0'60 0'78 0'60 0'20 0'12 0'75 0'69
1'00 1'00 0'98 0'97 0'24 0"23 0"78 0"71
1'00 I '00
0'29 0'28 0'78 0'70
1'00 I '00 0'31 0'19
1 '00
1'00
52
M. A. Rahman e t al.
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Lung function in Bangladeshi teenagers restrained by a difference of0.151 of FVC. Bangladeshi teenagers showed a comparable FEVI% (89% in boys and 87% in girls) despite having lower FVC than Europeans. This figure is more than that observed by Udwadia et al. (11) in their 15-19 year group. Several factors like age, height and build, ethnicity, customary physical activity, exposure to dust or smoke and nutritional status have all been shown to influence the normal lung function values (see reference 1). In teenage boys and girls these are futher complicated by the differences in the growth pattern in the two sexes. in European children it has been shown in important longitudinal studies (32a,b, 33; see also 34) that the adolescent spurt in girls takes place two years earlier than the boys, and that girls become taller and heavier at 9 or 10 and remain so until 14.5. At around 14 years the girls are surpassed by boys when the spurt in the latter has started whereas that in the former is finished. The fact that (a) ours was a cross-sectional and not a longitudinal study and (b) the age range considered was only from 12 to 19 years, make comments on the pubertal status of the sample studied unreliable. However, the following lines of evidence within our data suggest that the peak of the growth spurt in Bangladeshi girls is around 12 years while that of the boys is between 13 and 14 years. Firstly, although the mean height of the girls are lower than the boys, the lowest class of standing heights (1.37-1.39 m) contains only boys. The average rate of growth of girls declines rapidly after the age of 12 years and approaches zero after 15 years. In the boys, the peak increase in the growth rate takes place at around 14 years, as has also been observed in European boys (35). Tanner (35) reported that the increase in stature during the growth spurt is attributable more to the increase in trunk length (i.e. sitting height) than in leg length, and that the respiratory developments follow later. In the present study the effects of stature on lung function variables are evident throughout the age range in boys, but are better seen in girls before 15 years. In other words, in the late teens the age effect on forced expiratory variables is diminished or lost in girls, and the differences in ventilatory function in boys and girls in late teens can be explained by the 'sexual dimorphism of skeleton at puberty' (35). It is notable however that the correlations of expiratory variables with height or sitting height were still strongly positive. This has been expressed in the regression equation (see following). PEFR in both the sexes had the highest correlation with either sitting or standing height. Although age has an effect on PEFR independently of height (36), several other factors also matter. These include airway resistance, maximum voluntary muscular effort and possibly a compressive effect of the manoeuvre on the
53
intrathoracic airways (36). The longer period of male adolescence (1), and the continuation of growth with increased muscularity in boys during their late teens (37), explains the progressive separation of the mean PEFR values in boys and girls after 15 years of age. However, in the early teens the girls showed greater mean PEFR than boys. That can be similarly explained by an earlier adolescent spurt in muscle mass (35) and height in girls. Sitting height and standing height were found to be equally reliable indicators of lung function in Bangladeshi teenage boys and girls. Either could be used to predict the lung function variables. For PEFR, however, standing height was a marginally better predictor in girls and sitting height in boys (Table 5). That both age and weight are predictors of PEFR (Table 5) is to be expected since they are significantly correlated (Table 4). In girls under 15 years and all the boys, weight correlated with age (Table 4). Primhak et al. (36) showed that under 16 years the effect of age was linear in girls and curvilinear in boys. Godfrey et al. (38) examined age as an alternative to height in the prediction of PEFR. In a study in Indian children and adults, Gupta and Mathur (39) showed that in girls below 16 years and boys below 21 years, age was a contributing factor to PEFR in addition to height. In the part of the age range common to the present study and that of Gupta and Mathur (39), the findings in Indians and Bangladeshis are similar. It is intriguing that when analysed by step-wise regression, age was a second variable to sitting height in boys whereas age was eliminated from the equation for the girls by weight. Boys gain in both height and weight throughout their teens whereas in girls over 15 years the gain is almost entirely attributable to increase in muscle and fat. Thus, weight appeared as the second variable in the prediction equation in girls. However, since weight is the most inconstant variable and includes fat as well, equations with or without weight are also given to predict mean PEFR in Bangladeshi boys and girls. The linear models were considered for our population since Gupta and Mathur (39) reported the best fit of PEFR by a linear model after considering 11 different models in Indian boys and girls. The equation with height and age accounted for about 64 and 58% of the variance in PEFR in boys and girls, respectively. The amount not accounted for could be governed either by systematic effects not included or by random variation (39). We did not measure airway resistance, fat free mass or the compressive effect of the manoeuvre on the intrathoracic airways. The results for FVC and FEV~ in the present investigation were compared with similar studies conducted in teenagers of other ethnic origins with a view to estimating the
M. A. Rahman et al.
54
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Fig. 2 Comparison of FVC of the present study (with 1 SD)
in relation to height with those of separately published study in other groups (standard deviations omitted for clarity). The asterisk (*) indicates significantdifference (P < 0.05) between Bangladeshi and Libyan boys at that height category. [r-I, Jordanian boys (n = 46, P < 0.05); II, European boys (n = 45, P < 0.05); ~, Chineseboys (n-- 47, P < 0'05); ff],Libyan boys (n =48); <>,present study]
influence ofethnicity on lung function indices (Fig. 2). The possibility of wide variation in normal values of ventilatory capacity from one ethnic group to another was first pointed out by Myers (40). Later works of many investigators alleged that, apart from stature, ethnicity is a major constitutional factor that influences lung function variables. However, there is evidence of significant difference in results obtained from within the Indian subcontinent even between two contiguous populations (Madya Pradesh and Gujrat) in India (41, 42) where large ethnic differences would not be anticipated. Mean lung function values obtained by Chatterjee (12), Kamat et al. (43) and Verma et aL (1 O) in adults, differ from one another significantly after standardization for sex, age and height. Patrick and Patel's (44) figures for FVC in Indian children in Britain are different from those of Bhattacharya and Bannerjee (16) and Jain and Ramiah (8) for Indian children in India. Part of this variability can be attributed to the diversity of the genetic constitution of population groups. However, much also depends on environmental conditions not only o fdifferent regions in the Indian subcontinent but also, even more markedly, between the continents. These are likely to affect the growth of that group (and presumably also growth of their ventilatory function) differentially. The present results are similar to those reported by Bhattacharya and Bannerjee (16). Comparison with separately published results show that Bangladeshi teenage boys have lower FEVs than those of Euopeans (45), Jordanians (46) or Chinese teenagers (47) of same height (see Fig 2). Differences also become apparent between values for Bangladeshi and Libyan children (48) at heights of
more than 1.55 m. These samples undoubtedly differ in important environmental factors such as nutrition, altitude and climate, but also include ethnic differences. Even the ethnic factor is not a simple one. Differences in ethnic groups can be partly attributable to differences in body proportion and, in particular, trunk lengths (34), and also to putative differences in the pattern and rate of growth between different ethnic groups. Ethnic as well as environmental influences on age at puberty must also play a role. In the absence of convincing means of distinguishing ethnic and environmental effects, it follows that serious attempts to assess individual or group ventilatory status must depend on use of norms derived from a population of similar environment and ethnicity to the subjects. Further studies, especially direct comparisons between different groups, with special reference to the pubertal development, would focus more light on these matters. This study provides a source of normal values for forced expiratory indices in Bangladeshi teenagers. A group of healthy and well-nourished children of better economic background was considered for the sake of homogeneous environmental conditions, e.g. nutrition, physical activity and living conditions. It is possible that tests carried out with random samples from teenagers in Bangladesh would show results different from those reported here.
Acknowledgements This work was supported, in part, by the Association o fCommonwealth Universities. The authors gratefully acknowledge the hospitality and cooperation of the Cadet College authorities, especially the Principals, the medical officers, the paramedical staffand the adjutants during the visits, all the cadets for their great enthusiasm, Dr A H Short for helping to prepare the manuscript and Professor T. Bennett for revisions, and Dr S. Bhadra and Dr J.M. Patrick for their helpful critique.
References 1. Cotes JE. Lung Function: Assessment and Application in Medicine. 4th ed. Oxford: Blackwell Scientific Publications, 1979. 2. Cherniank RM. Ventilatory function in normal children. Can JMed 1962:87: 80-81. 3. Polgar G, Promadhat V. Pulmonary Function Testhlg in Children: Techniques and Standards. Philadelphia: W.B. Saunders, 1971, pp. 1-273. 4. Miller GJ, Ashcroft MT, Swan AV, Beadnell HMSG. Ethnic variation in forced expiratory volume and forced vital capacity of African and Indian adults in Guyana. Am Rev Respir Dis 1970; 102:979-98 I. 5. Miller G J, Saunders M J, Gilson RJC, Ashcroft MT. Lung function of healthy boys and girls in Jamaica in
L u n g f u n c t i o n in Bangladeshi teenagers
6. 7. 8.
9. 10.
I I. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.
23. 24. 25. 26. 27. 28,
relation to ethnic composition, test exercise perfomance and habitual physical activity. Thorax 1977; 32: 486-496. Mustafa KY. Spirometric lung function tests in normal men of African ethnic origin. Am Rev Respir Dis 1977; 116: 209-213. Jain SK, Ramiah TJ. Prediction ofventilatory 'norms' in healthy boys 7-14 years age. Indian J Chest Dis 1967: 10: 69. Jain SK, Ramiah TJ. Normal standards of pulmonary function tests for healthy Indian men 15-40 years old. Comparison of different regression equations (prediction formulae). Indian J M e d R e s 1969: 57: 1453-1463. Meenaxmi K, Singh HD. Lung function in school boys. lndian J Physiol Pharmaco11971: 15(2): 19. Verma SS, Kishore N, Raman CV, Lakhera SC, Das SK. Prediction of some ventilatory 'norms' in healthy Indian males of 21-69 years age. Indian J Physiol Pharmacol 1983: 27: 45-49. Udwadia FE, Sunavala JD, Shetye VM, Jain PK. The maximal expiratory flow-volume curve in normal subjects in India. Chest 1986: 89: 852-856. Chatterjee S, Saha D, Chatterjee BP. Pulmonary funtion studies in healthy non-smoking men of Calcutta. Ann Hum Bio11988; 15: 365-374. Malik MA, Moss E, Lee WR. Prediction values for the ventilatory capacity in male West Pakistani workers in United Kingdom. Thorax 1972; 27:611-619. Williams DE, Miller RD, Taylor WF. Pulmonary function studies in healthy Pakistani adults. Thorax 1978; 37: 243-249. Ayub M, Zaidi SH, Burki NK. spirometry and flowvolume curves in healthy, normal Pakistanis. Brit J Dis Chest 1987: 81: 35-43. Bhattacharya AK, Banerjee S. Vital capital in children and young adults in India. lndian J Med Res 1966; 54: 62-71. Bhatia SL. The vital capacity of the lungs, lndian Med Gazette 1929; 04: 519-521. Sobol T, Read J. Maximal expiratory flow rates in Australian adults. Aust Ann Med 1961; 10: 49-51. Laszlo G. Standardised lung function testing. Thorax 1984; 39: 881-889. American Thoracic Society: Standardization of spirometry 1987 update. Am Rev Respir Dis 1987; 136: 1285-1298. Weiner JS, Lourice JA. Human Biology--A Guide to Field Methods Oxford: Blackwell Science Publishers 1969. Melia RJW, Swan AV, Clarke G, Florey C du Ve, Nelson AN. Technical note: Suitability of a new turbine spirometer for epidemiological surveys in children. Bull Eur Physiopath Resph- 1985; 21: 43-48. Chowenczyk P J, Lawson CP. Pocket-sized device for measuring forced expiratory volume in one second and forced vital capacity. Brit M e d J 1982; 285: 15-17. Gunawardena RA, Houston K, Smith AP. Evaluation of the turbine pocket spirometer. Thorax 1987; 42: 689-693. Fairnbairn AS, Wood CM, Fletcher CM. Variability in answers to a questionnaire on respiratory symptoms. Br JPrev Soc Med 1959; 13: 175-193. Townsend MC. Spirometric forced expiratory volumes measured in the standing versus the sitting posture. A M Rev Respir Dis 1984; 130: 123-124. De P and De BN. The vital capacity of the Bangalees. Indian MedGazette 1939; 74: 409-414. Mukherjee HN, Gupta PC. The basal metabolism of Indians (Bengalees). Indian J Med Res 1931; 18: 807.
55
29. Strang LB. The ventilatory capacity of normal children. Thorax 1959; 14: 305-310. 30. Leeder SR, Swan AV, Peat JK, Woodclock AJ, Blackburn CRB. Maximum expiratory flow volume-curves in children: changes with growth and individual variability. Bull Eur Physiopath Respir 1977; 13: 249-260. 31. Taussig LM. Maximal expiratory flows at functional residual capacity: a test of lung function for young children. A M Rev Respir Dis 1977; 116:1331-1338. 32a Tanner JM, Whitehouse RH, Takaishi M. Standards from birth to maturity for height, weight and height velocity and weight velocity; British chidren, 1965. Arch Dis Child 1966; 41: 454--471. 32bTanner JM, Whitehouse RH, Takaishi M. Standards from birth to maturity for height, weight and height velocity and weight velocity; British chidren, 1965. Arch Dis Child 1966; 41: 613-635. 33. Tanner JM, Whitehouse RH. Clinical longitudinal standards for height, weight and height velocity and weight velocity and the stages of puberty. Arch Dis Child 1976; 51: 170-179. 34. Tanner JM. Human Growth (F Falkner, J Tanner, eds) 2nd ed, London: Plenum Press, 1986. 35. Tanner JM. Puberty, In: Foetus into Man London: Open books, 1978; 69 pp. 36. Primhak R_A,Biggins JD, Tsanakas JN, Hatzimiehael A, Milner RDG, Karpouzas JG. Factors affecting the peak expiratory flow rates in children. Br JDis Chest 1984; 78: 26-35. 37. Koch G. Standardization of lung function testing in infants, children and adolescents. Bull Europ Physiopath Respir 1983; 19: 15-24. 38. Godfrey S, Kamburoff PL, Nairn JN. Spirometry, lung volumes and airway resistance in normal children aged 5-18 years. Br JDis Chest 1970; 64: 15-24. 39. Gupta CK, Mather N. Statistical model relating peak expiratory flow rates to age, height and weight in men and women. JEpidemiol Commun Hlth 1982; 36: 64-67. 40. Myers JA. Vital Capacity of the Lungs Baltimore, Maryland: Williams and Wilkins Company, 1925; pp, 32-35. 41. Bhargava RP, Misra SM, Gupta NK. Ventilatory tests and lung volume studies in Madhya Pradesh-Physiological norms. Indian J Physiol Pharmacol 1973; 17: 267-272. 42. Talsania RC, Phadia EG, Goel TP. Vital capacity and maximum breathing capacity in Gujrathis. Indian J Physiol Pharmaco11965; 9: 67-74. 43. Kamat SR, Tyahi NK, Rashid SSA. Lung function in Indian adult subjects. Lunglndia 1982; 1:11-21. 44. Patrick JM, Patel A. Ethnic differences in the growth of lung function in children. Ann Hum BioI 1986; 13: 307-315. 45. Polgar G, Promadhat V. Pulmonary Function Testing in Children: Techniques and Standards. Philadelphia: W.B. Saunders Co, 1971 46. Sliman NA, Dajani BM, Shubair KS. Pulmonary function in normal Jordanian children. Thorax 1982; 37: 854--857. 47. Lain KK, Pang SC, Allan WGL et al., Predictive nomograms for forced expiratory volume, forced vital capacity and peak expiratory flow rate in Chinese adults and children. Brit J Dis Chest 1983; 77: 390-396. 48. Shamssain MH, Thompson J, Ogston SA. Forced expiratory indices in normal Libyan children aged 6-19 years. Thorax 1988; 43: 467-470.
Lung function in teenage Bangladeshi boys and girls M.A. RAHMAN,M.B. ULLAH* and A. BEGUMt
Department of Physiology and Pharmacology, Medical School, Queen'sMedical Centre, Universityof Nottingham, Nottingham NG7 2UH, U.K. Data on forced vital capacity, forced expiratory volume in one second and peak expiratory flow rate were obtained in a group of 588 healthy and well-nourished (but not obese) Bangladeshi teenagers to establish normal values in this population. Bangladeshi girls in their early teens showed higher peak expiratory flow rates than boys of the same age but while this continued to rise in boys after the age of 15 years the peak expiratory flow rate in girls seemed to have attained its maximum values by that age. Correlations between sitting height and the lung function variables were found to be marginally greater than those with standing height. Prediction equations were calculated for each lung function variable with sitting and standing separately. Comparison of the results in our study with those reported from other ethnic groups indicate that Bangladeshi values are lower than those of Europeans, Jordanians or Chinese but not significantly different from those reported for Libyans. Since in practice, genetic, nutritional and environmental factors are not readily disentangled, norms for a given study population need to be derived from healthy subjects of similar background and ethnicity.
Introduction Lung function measurements are important aids to diagnosis and are also important guides to therapy in patients with respiratory diseases. Standard values of lung function indices for Europeans of all ages have been established (1-3). Considerable work has been done on Afro-Carribean subjects (4-6), and on children (7-9) and adults of Indian (10-12) or Pakistani origin (13-15). Very little is known, however, about lung function values in teenagers of the Indian subcontinent although teenagers constitute a substantial proportion of the population in Bangladesh and India. There is only one study, by Bhattacharya and Bannerjee (16), that reports data from Indian teenage boys and girls, Workers involved with the earliest lung function surveys in the Indian subcontinent emphasized the need for standardization of lung function indices on the basis of ethnicity and environment (17). Sobol (18) commented that every laboratory should have its own standard lung function values. Williams (14) stressed that standard values for a geographical population should be derived from a sample specific to that area. The need for information about lung function in healthy subjects from homogeneous populations Received 24 April 1989 and accepted 27 September 1989 *Current address: Jhenaidah Cadet College, Jhenaidah, Bangladesh. tCurrent address: Maeleod Road, Kotchandpur 7330, Jhenaidah, Bangladesh.
0954-6111/90/010047+ 09 $03.00/0
within a community between the ages 15 and 30 has been publicized (19), and in a recent review on spirometry (20) the comment was made that 'few data are available for several race and age groups'. In addition, with better understanding of respiratory mechanics, and with constant refinement of instruments and changing techniques, it is desirable that periodic assessments &normal values of lung function are carried out with a view to establishing more dependable and accurate data, especially in a field where few data are available. The present study was undertaken to establish, in Bangladeshi teenage boys and girls, standard values for the most commonly measured lung function variables, namely, forced vital capacity (FVC), forced expiratory volume in one second (FEV 0, [FEVJFVC]100 (FEV1%), and peak expiratory flow rate (PEFR) using a portable electronic spirometer.
Methods LOCATIONAND SUBJECTS The study was carried out at Jhenaidah Cadet College and Mymensing Girls' Cadet College (100 miles southeast and 60 miles north of Dhaka, respectively, and both at sea level). Measurements were made at a temperature of 27-31~ and a humidity of 87-93% from mid July to early September, during normal working hours, To obtain a uniform sample for reference values, a selected group of healthy 9 1990Bailli~reTindal]
48
M . A. R a h m a n et al.
Bengalee boys and girls (total of 588 subjects; 298 boys and 290 girls), aged between 12 and 19 years from these residential colleges were chosen for study. Children enter the colleges at the age of 12-13 years and stay there f o r the next 6 years. They have similar diet and training. H o u r long morning physical exercise and afternoon games and sports are mandatory for all. Height, weight and general health (including menstrual status in girls) are recorded at the begining and end of every term. Before the measurements were made, the governing body o f the Cadet Colleges was approached for permission to carry out the survey. (It was agreed that girls would be asked no questions regarding their pubertal status. However, we were allowed to use the existing records confidentially for our survey). Pubertal status for the boys was not defined. Prospective subjects were asked to answer questions set according to the I987 recommendation by the American Thoracic Society. Screening was carried out by medical officers of the respective colleges to exclude those with c o m m o n cold or other respiratory diseases, Those with a history of food allergy were included as long as they showed no respiratory signs or symptoms at the time of study. A lecture was given describing the whole procedure, making the children familiar with the instrument and techniques to be used during the survey. They were then given disposable cardboard mouthpieces for practice.
INSTRUMENTS
A 'pocket monitor' (Micro Medical Instruments, PO Box 6, Rochester, Kent, U.K.) was used for spirometry, It consists of a transducer head assembly connected by a length of cable to a battery-powered microprocessor control unit. This unit converts the electrical pulses generated by a turbine in t[ae transducer head into FVC, FEV~, and PEFR measurements on a digital display. The instrument was chosen after considering a report of its feasibility for epidemiological surveys by Melia et al. (22). Although the accuracy of similar instruments has been described by Chowienczyk and Lawson (23) and Gunawardena et al. (24), before carrying out the present survey the instrument to be used was calibrated in Nottingham by connecting it in series with an Ohio spirometer (Ohio Inc. Houston, Texas) in the lung function laboratory. The accuracy of FVC, FEV~ and PEFR measurements with the pocket monitor were found to be within __+3% of the standard spirometer values with Euopean as well as with Asian subjects. During the survey, after every 20 subjects tested, the monitor was calibrated with a 21 syringe which was discharged smoothly and evenly. The pocket monitor read 1.051 when 11 of air was discharged and 2. l 1 when 21 were discharged from the syringe. The readings were adjusted accordingly in the analysis of results. (No changes were observed in calibration with repeated measurements throughout the survey.
ANTHROPOMETRIC MEASUREMENTS
Age was calculated from the recorded date of birth for each b o y and girl. Subjects in the age range 12 years to 12 years 11 months were grouped in age group 12, those f r o m 13 years to 13 years 11 months in age group 13, and so on. Body weight was measured to the nearest 0.25 kg, with subjects wearing similar clothes, using a calibrated weighing machine (Krups, Ireland). Standing height was measured to the nearest 0.25 cm using a staxtiometer (21) with subjects in bare feet. Sitting height was taken with the subjects seated with the vertex maximally extended position on a flat w o o d e n chair, looking straight ahead with their knees flexed to a right angle. All the measurements were taken within 2 weeks before the lung function measurements b y the respective medical officers and three paramedical staff in each college accustomed to the routine performance of these measurements (six times per year f o r each pupil), For the present purposes, they were asked to follow strictly the IBP guidelines (21). There were few discrepancies from the routine measurements taken within the previous month,
PROCEDURE Although several people were involved in the anthropometry, the ventilatory measurements were all supervised by the same person (AR) to minimize interobserver variation as shown by Fairbairn et aL (25). The measurements were taken with the subjects in a standing position (26); nose clips were not used. Subjects were asked to breathe in fully and unhurriedly, then to close the lips round the mouthpiece and blow out as hard and as fast as they could without any pause. They were verbally encouraged during the procedure to squeeze out all air. It was ensured that belts were loosened, no pursing of the lips occurred and that subjects did not obstruct the mouthpiece with the tongue. At least 30 s was allowed between each blow. To achieve acceptable reliability of measurement according to the 1987 ATS guidelines, subjects were asked to deliver at least three but not more than eight blows until the best FVC values differed by 0'151 or less. Eighteen subjects (16 girls and two boys) were unable to achieve this by the eighth blow and were excluded. In fact, apart from these excluded subjects, data from
Lung function in Bangladeshi teenagers 49 four o r five blows were recorded for each subject, The largest FVC and FEV~ were noted even if the two values came from separate blows (20). The largest values of the FEVI/FVC% for each of the recorded blows were also noted.
1.8
_~
1.7
1.6 STATISTICAL
ANALYSIS
Data from the blows having the best three FVC values were considered for analysis (20) using a stepwise regression method. Sex was used as a main factor with age, weight, and standing height and/or sitting height as covariates. Since logarithmic transformation did not diminish any of the residual variances, we performed multiple linear regression analysis of the ventilatory variables on age, weight, standing height and sitting height as untransformed covariates. Prediction equations were calculated for each lung function variable with sitting height and standing height separately. Results ANTHROPOMETRIC
RESULTS
The data on five different anthropometric variables are presented in Tables 1 and also in Tables 2 and 3. The least height in both boys [1.40m (mean 1.50 -t-0.06)] and girls [1.37 m (mean 1.49 _+0.06)] were observed at age 12, and the greatest height at age 19 in boys [1'79 m (mean 1.69 +__0.04)) and 18 in girls [1'68 m (mean 1.57_+0.04)]. The mean increase in height in girls between age 12-15 years was 6cm while that between 15-18 years was 1 cm. On the other hand, boys showed an almost steady growth from 12 through to 19 years (Table 2). The mean height observed at different ages in boys and girls are shown in Fig. 1. Nineteen girls from the age range 12 (42% of the sample group age 12) and two girls from age range 13 had not reached their menarche at the time of survey, according to the records in the college. It should also be noted that the college selection process would have excluded overweight subjects. The range of BMI (kg m -z) in this population was boys 13.3 to 26.8, girls 13.7 to 23.8 (Table 1). It was not therefore, possible to consider effects of obesity in this study. FVC ANDFEV~ The values of different lung function variables are presented according to age (Table 2) as well as according to height (Table 3). FVC and FEVI increased steadily in boys throughout the age range. In the girls, both levelled off at about 15 years of age (Table 2). The ventilatory function values in premenarcheal girls were similar to those of the rest of the age group. The matrix in Table 4 shows significant positive cor-
1.5
1.4
~
II
I
[2
~
I
15
i
I
,
1
1
I
14 15 16 Age (years)
I
[
17
I
I
18
i
.I
19
Fig. 1 Comparison of height in Bangladeshi teenage boys (I-1) and girls (I1~).Measurements are defined as mean with one standard deviation. (SD shown by bars). relations of FVC and FEVi, with all four anthropometric variables in both sexes. Correlation of FVC and FEV~ with sitting height was marginally better than standing height followed by age and weight, respectively. On this basis separate prediction equation were derived with sitting or standing height as covariates. Although in all cases weight showed significant correlation (Table 4), it contributed little that was not covered better by the other variables and was therefore eliminated in the step-wise regression analysis (summarized in Table 5). FEV1% AND PEFR Highest values of FEVI % from the accepted blows for each subject were recorded (Table 5). These were not different from the FEV~% derived from the separate highest FEV 1 and FVC values (boys:mean 88.6%, SD2' 1; girls:mean 86'5%, SD2"3). FEV 1% did not show a significant correlation with any of the anthropometric variables either in boys or in girls. No regression equation is therefore presented. PEFR resembled FVC and FEVa in its correlations with the anthropometric variables, except in that weight was a significant factor (Table 4). The correlation value, r, for PEFR and age was more in boys (0.76) than in girls (0'50). This r-value increased (0.59) in girls when only age range 12-15 years was considered. Weight was retained in the equation even at the cost of height or sitting height when analysed by step-wise regression method (see Table 5). Though the effects of standing and sitting heights were closely similar in both sexes, standing height was a marginally better predictor in girls, and sitting height in boys. Discussion
Although some measurements of lung function carried out in the Indian population have included
50
M. A, Rahman et al. Table 1 Anthropometric data of Bangladeshi healthy teenagers
Boys (n =296)
Girls (n = 274)
Mean (SD)
Range
Mean (SD)
Range
15.5 (2,0) 47-1 (8-9) 1.62 (0.1) 0,83 (0,05) 51.3 (1'0) 17,9 (2,2)
12.0-19.0 25.0-73.0 1.37-1.79 0.69-0.94 49.0-54.0 13.3-26,8
14.11 (2'0) 44.0 (5.9) 1"54 (0,5) 0.77 (0,02) 50,3 (0.06) 18.4 (2.0)
12,0-18.9 27'7-61,0 1,40-1.68 0.71--0,85 48,8-52.1 13.7-23.8
Age in years Weight (kg) Standing height (m) Sitting height (m) Sitting: Standing height (%) Weight for height (kgm -2)
Table 2 Data in relation to age in Bangladeshi boys and girls
Age (years) 12 13 14 15 16 17 18 19 Total
Sex
No.
Ht (m)a
Sht (m)b
Wt (kg)c
FVC (1)d
FEV~ (1)~
FEVJ FVC%
PEFR (1 min-~)
Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Boys Girls
46 45 40 53 26 40 37 41 46 18 45 45 54 36 2 296 278
1,49(0.009) 1.50(0.006) 1'56(0.007) 1.52(0.006) 1-60(0,007) 1,54(0.007) 1-62(0.007) 1.56(0,006) 1,66(0.006) 1-57(0.012) 1.67(0.007) 1.58(0,007) 1.69(0,006) 1.57(0,007) 1.75(0.000) 1.62(0.005) 1.54(0.003)
0.75(0.005) 0"75(0.003) 0"79(0.004) 0,76 (0.003) 0"81(0.004) 0.77(0,004) 0"83(0.004) 0"79(0,003) 0,86(0.004) 0.79(0-006) 0,87(0,004) 0,79 (0.003) 0.88 (0.003) 0.79 (0,004) 0,92(0.005) 0.83 (0,003) 0,78 (0.002)
34.9(0.83) 39,3(0,77) 42.0(0.80) 40.6(0.69) 42,8(0.92) 44.3(0,70) 47,0(0.99) 46.8(0.74) 50.9(0,74) 45'9(1.31) 52.8(i,00) 46'9 (0.76) 55'1(0.85) 47.2(0,89) 56'3(2.75) 47'I (0,52) 44,1 (0.35)
2,03(0,047) 1.92(0.034) 2.42(0,041) 2,04(0.032) 2.60(0"045) 2,14(0.038) 2.78(0.028) 2,33(0.035) 2.97(0.031) 2.39(0"058) 3,06(0,048) 2.47(0,037) 3,19(0,048) 2'38 (0.043) 3,67(0.175) 2.75(0'028) 2.21(0,019)
1.79(0.043) 1.64(0,029) 2,13 (0.038) 1.76(0,029) 2.30 (0.040) 1'83(0'032) 2.45(0.025) 2.02(0.034) 2.65(0,029) 2.08 (0'052) 2,73 (0.045) 2.17(0'035) 2.84(0,044) 2.08 (0,037) 3.28(0,135) 2.44(0,026) 1.92(0.017)
88,5 (0.26) 86,9(0,3l) 89,0 (0.25) 87.6(0,26) 89,2 (0.33) 87.7 (0.25) 89,1(0,22) 87,6 (0,36) 89,5 (0.24) 88,8 (0'37) 90,0(0'26) 88.6(0,33) 89,4(0,21) 88,8 (0,24) 89,6(0,58) 89,2(0,09) 87,9 (0,12)
312 (7"3) 354(3'9) 349 (7"3) 371 (3,7) 372 (9'5) 385 (4.7) 410(9,9) 400(4,1) 447 (8,4) 395(7,7) 466 (8.2) 397 (4,0) 487 (8,3) 402 (5,5) 518(5.0) 412 (4.8) 384(2,0)
~Ht(m)= standing height in metres bSht(m)= sitting height in metres CWt(kg)= weight in kg aFVC = forced vital capacity in litres 'FEV~= forced expiratory volume in litres in 1 s rPEFR =peak expiratory flow rate in litres per min Values are mean (standard error): all volumes are in BTPS. Bengalees (17,27,28), no systematic study has been carried out in the Bangladeshi population, The present study was therefore undertaken to establish a reference standard for a teenage population of Bangladesh. The results of this study indicate that in Bangladeshi teenage boys and girls the forced expiratory volumes increase with age, Bangladeshi girls have a lower FVC compared to those of boys of similar age, weight, height or sitting height, except during the early teens when both boys and girls show similar values. Such differences also existed in FEV~ in boys and girls of the same age and the differences remained even when heights were taken into account. These findings are not
in agreement with the observation that differences in FEV l in children between sexes disappear if height is taken into account (29). Bangladeshi girls in their early teens showed higher P E F R than boys of the same age, as has previously been reported for children of European descent (30, 31). However, while P E F R continued to rise in boys after the age of 15 years, P E F R in girls seemed to have attained its maximum values by that age. There were no differences between the mean of the highest values of FEV 1% from the accepted blows for each subject and the FEV~ % derived from the separate highest FEV~ and FVC values. This is not unexpected since the selection criteria for the acceptable blows were
Lung function in Bangladeshi teenagers
51
Table 3 Data in relations to heights in Bangladeshi boys and girls Ht(m)~
No.
Sex
Age(years)
Sht(m)b
Wt(kg)~
FVC(1)d
FEV,(1) c
FEV1%
PEFR (Ira-t )
!.37-1,39 1.40-1.44
5 6 4 21 43 19 102 54 83 68 37 77 9 35 11
Boys Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Boys
12.2(0.11) 12.4 (0.1 I) 12.0(0.00) 12.7 (0.06) 13.1 (0.17) 13'1 (0.16) 14'6(0'20) 14.2(0.19) 15.6(0.19) 15.6 (0.20) 16.0(0.25) 16.7(0,13) 17.1(0.36) 17.4 (0.16) 18,2(0.24)
0,70(0.005) 0.72(0.004) 0'71(0'002) 0.75(0.003) 0.74(0.001) 0.77(0.002) 0.77(0'001) 0.80(0.002) 0,79(0.001) 0,83(0.003) 0.81(0,002) 0,86(0,002) 0.83(0.01I) 0.89(0'003) 0.91(0.004)
27.8(1.3) 30.6(0.9) 34.6(3.8) 35.6(1.2) 38'0(0.7) 36.8(0.5) 43.1(0.4) 42.4(0.7) 45.9(0.5) 48.5 (0"7) 48.2(5.5) 51.8(0.7) 53.2(0.8) 55.9(0.9) 58.6(1.9)
1.58(0.08) 1.68(0.06) 1.53(0.04) 2.03(0.04) 1.82(0,02) 2.19(0.05) 2.11(0.02) 2'58(0'03) 2.36(0.02) 2'80 (0.03) 2.60(0'03) 2,98(0.02) 2.80(0.06) 3.22(0'05) 3.74(0,14)
1.39(0,08) 1.45 (0.05) 1.31 (0.05) 1.78 (0.04) 1.56(0.02) 1.93 (0.04) 1.83 (0.02) 2.28(0.03) 2.04(0.02) 2.48 (0.02) 2,21(0.03) 2.65(0,02) 2.49(0.06) 2.88 (0.05) 3.36(0.12)
88(0.7) 86 (1.2) 85(1"7) 88 (0.4) 86(0.4) 88(0'3) 87(0'2) 88(0'2) 86(0.2) 88 (0,2) 87(0'3) 89(0.2) 89(0.6) 89 (0.3) 89(0.4)
281(19.7) 264 (17.2) 306 (5"4) 315 (11.0) 349 (3.2) 321 (9.0) 377 (2.1) 370 (7'4) 394 (2.4) 423 (8.0) 414 (3.8) 450 (5.6) 450(13.2) 498 (10'6) 508(15.9)
1.45-1.49 1.50-l.54 1.55-1.59 1.60-1,64 1.65-1,69 1.70-1.74 1,75-1.79
.'Ht(m) = standing height in metres ~Sht(m) = sitting height in metres 'Wt(kg) = weight in kg dFVC = forced vital capacity in litres ~FEV~--forced expiratory volume in litres in 1 s rPEFR = peak expiratory flow rate in litres per min Values are mean (standard error), all volumes are in BTPS
Table 4 Simple correlation coefficients between lung function measurements and different anthropometric variables in healthy Bangladeshi teenage boys and girls Age (years) Age (years) Ht(m) Sitting Ht(m) Wt(kg) FVC(1) FEV~(1) FEVt% PEFR(I m-~)
Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls
Ht(m)~ Sht(m)~ Wt(kg)c FVC(1)~
FEVf(1)~
FEV~% PEFR(lm-t)r
1.00 1.00
0.81 0'54 0.84 0.56 0.77 0.50 0,82 0,63 0.82 0.65 0.20 0.23 0,76 0,50
1'00 1'00 0.96 0.95 0.82 0.63 0.90 0.87 0.88 0.83 0.20 0.09 0'76 0'75
~Ht(m) = standing height in metres bSht(m) -sitting height in metres ~Wt(kg)---weight in kg aFVC = forced vital capacity in litres ~ = forced expiratory volume in litres in 1 s rPEFR = peak expiratory flow rate in litres per rain
1.00 1.00 0.83 0.63 0.90 0.91 0.89 0.88 0.21 0.09 0.80 0.73
1'00
1'00 0'78 0'60 0'78 0'60 0'20 0'12 0'75 0'69
1'00 1'00 0'98 0'97 0'24 0"23 0"78 0"71
1'00 I '00
0'29 0'28 0'78 0'70
1'00 I '00 0'31 0'19
1 '00
1'00
52
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Lung function in Bangladeshi teenagers restrained by a difference of0.151 of FVC. Bangladeshi teenagers showed a comparable FEVI% (89% in boys and 87% in girls) despite having lower FVC than Europeans. This figure is more than that observed by Udwadia et al. (11) in their 15-19 year group. Several factors like age, height and build, ethnicity, customary physical activity, exposure to dust or smoke and nutritional status have all been shown to influence the normal lung function values (see reference 1). In teenage boys and girls these are futher complicated by the differences in the growth pattern in the two sexes. in European children it has been shown in important longitudinal studies (32a,b, 33; see also 34) that the adolescent spurt in girls takes place two years earlier than the boys, and that girls become taller and heavier at 9 or 10 and remain so until 14.5. At around 14 years the girls are surpassed by boys when the spurt in the latter has started whereas that in the former is finished. The fact that (a) ours was a cross-sectional and not a longitudinal study and (b) the age range considered was only from 12 to 19 years, make comments on the pubertal status of the sample studied unreliable. However, the following lines of evidence within our data suggest that the peak of the growth spurt in Bangladeshi girls is around 12 years while that of the boys is between 13 and 14 years. Firstly, although the mean height of the girls are lower than the boys, the lowest class of standing heights (1.37-1.39 m) contains only boys. The average rate of growth of girls declines rapidly after the age of 12 years and approaches zero after 15 years. In the boys, the peak increase in the growth rate takes place at around 14 years, as has also been observed in European boys (35). Tanner (35) reported that the increase in stature during the growth spurt is attributable more to the increase in trunk length (i.e. sitting height) than in leg length, and that the respiratory developments follow later. In the present study the effects of stature on lung function variables are evident throughout the age range in boys, but are better seen in girls before 15 years. In other words, in the late teens the age effect on forced expiratory variables is diminished or lost in girls, and the differences in ventilatory function in boys and girls in late teens can be explained by the 'sexual dimorphism of skeleton at puberty' (35). It is notable however that the correlations of expiratory variables with height or sitting height were still strongly positive. This has been expressed in the regression equation (see following). PEFR in both the sexes had the highest correlation with either sitting or standing height. Although age has an effect on PEFR independently of height (36), several other factors also matter. These include airway resistance, maximum voluntary muscular effort and possibly a compressive effect of the manoeuvre on the
53
intrathoracic airways (36). The longer period of male adolescence (1), and the continuation of growth with increased muscularity in boys during their late teens (37), explains the progressive separation of the mean PEFR values in boys and girls after 15 years of age. However, in the early teens the girls showed greater mean PEFR than boys. That can be similarly explained by an earlier adolescent spurt in muscle mass (35) and height in girls. Sitting height and standing height were found to be equally reliable indicators of lung function in Bangladeshi teenage boys and girls. Either could be used to predict the lung function variables. For PEFR, however, standing height was a marginally better predictor in girls and sitting height in boys (Table 5). That both age and weight are predictors of PEFR (Table 5) is to be expected since they are significantly correlated (Table 4). In girls under 15 years and all the boys, weight correlated with age (Table 4). Primhak et al. (36) showed that under 16 years the effect of age was linear in girls and curvilinear in boys. Godfrey et al. (38) examined age as an alternative to height in the prediction of PEFR. In a study in Indian children and adults, Gupta and Mathur (39) showed that in girls below 16 years and boys below 21 years, age was a contributing factor to PEFR in addition to height. In the part of the age range common to the present study and that of Gupta and Mathur (39), the findings in Indians and Bangladeshis are similar. It is intriguing that when analysed by step-wise regression, age was a second variable to sitting height in boys whereas age was eliminated from the equation for the girls by weight. Boys gain in both height and weight throughout their teens whereas in girls over 15 years the gain is almost entirely attributable to increase in muscle and fat. Thus, weight appeared as the second variable in the prediction equation in girls. However, since weight is the most inconstant variable and includes fat as well, equations with or without weight are also given to predict mean PEFR in Bangladeshi boys and girls. The linear models were considered for our population since Gupta and Mathur (39) reported the best fit of PEFR by a linear model after considering 11 different models in Indian boys and girls. The equation with height and age accounted for about 64 and 58% of the variance in PEFR in boys and girls, respectively. The amount not accounted for could be governed either by systematic effects not included or by random variation (39). We did not measure airway resistance, fat free mass or the compressive effect of the manoeuvre on the intrathoracic airways. The results for FVC and FEV~ in the present investigation were compared with similar studies conducted in teenagers of other ethnic origins with a view to estimating the
M. A. Rahman et al.
54
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1"40 1'45 I'
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Fig. 2 Comparison of FVC of the present study (with 1 SD)
in relation to height with those of separately published study in other groups (standard deviations omitted for clarity). The asterisk (*) indicates significantdifference (P < 0.05) between Bangladeshi and Libyan boys at that height category. [r-I, Jordanian boys (n = 46, P < 0.05); II, European boys (n = 45, P < 0.05); ~, Chineseboys (n-- 47, P < 0'05); ff],Libyan boys (n =48); <>,present study]
influence ofethnicity on lung function indices (Fig. 2). The possibility of wide variation in normal values of ventilatory capacity from one ethnic group to another was first pointed out by Myers (40). Later works of many investigators alleged that, apart from stature, ethnicity is a major constitutional factor that influences lung function variables. However, there is evidence of significant difference in results obtained from within the Indian subcontinent even between two contiguous populations (Madya Pradesh and Gujrat) in India (41, 42) where large ethnic differences would not be anticipated. Mean lung function values obtained by Chatterjee (12), Kamat et al. (43) and Verma et aL (1 O) in adults, differ from one another significantly after standardization for sex, age and height. Patrick and Patel's (44) figures for FVC in Indian children in Britain are different from those of Bhattacharya and Bannerjee (16) and Jain and Ramiah (8) for Indian children in India. Part of this variability can be attributed to the diversity of the genetic constitution of population groups. However, much also depends on environmental conditions not only o fdifferent regions in the Indian subcontinent but also, even more markedly, between the continents. These are likely to affect the growth of that group (and presumably also growth of their ventilatory function) differentially. The present results are similar to those reported by Bhattacharya and Bannerjee (16). Comparison with separately published results show that Bangladeshi teenage boys have lower FEVs than those of Euopeans (45), Jordanians (46) or Chinese teenagers (47) of same height (see Fig 2). Differences also become apparent between values for Bangladeshi and Libyan children (48) at heights of
more than 1.55 m. These samples undoubtedly differ in important environmental factors such as nutrition, altitude and climate, but also include ethnic differences. Even the ethnic factor is not a simple one. Differences in ethnic groups can be partly attributable to differences in body proportion and, in particular, trunk lengths (34), and also to putative differences in the pattern and rate of growth between different ethnic groups. Ethnic as well as environmental influences on age at puberty must also play a role. In the absence of convincing means of distinguishing ethnic and environmental effects, it follows that serious attempts to assess individual or group ventilatory status must depend on use of norms derived from a population of similar environment and ethnicity to the subjects. Further studies, especially direct comparisons between different groups, with special reference to the pubertal development, would focus more light on these matters. This study provides a source of normal values for forced expiratory indices in Bangladeshi teenagers. A group of healthy and well-nourished children of better economic background was considered for the sake of homogeneous environmental conditions, e.g. nutrition, physical activity and living conditions. It is possible that tests carried out with random samples from teenagers in Bangladesh would show results different from those reported here.
Acknowledgements This work was supported, in part, by the Association o fCommonwealth Universities. The authors gratefully acknowledge the hospitality and cooperation of the Cadet College authorities, especially the Principals, the medical officers, the paramedical staffand the adjutants during the visits, all the cadets for their great enthusiasm, Dr A H Short for helping to prepare the manuscript and Professor T. Bennett for revisions, and Dr S. Bhadra and Dr J.M. Patrick for their helpful critique.
References 1. Cotes JE. Lung Function: Assessment and Application in Medicine. 4th ed. Oxford: Blackwell Scientific Publications, 1979. 2. Cherniank RM. Ventilatory function in normal children. Can JMed 1962:87: 80-81. 3. Polgar G, Promadhat V. Pulmonary Function Testhlg in Children: Techniques and Standards. Philadelphia: W.B. Saunders, 1971, pp. 1-273. 4. Miller GJ, Ashcroft MT, Swan AV, Beadnell HMSG. Ethnic variation in forced expiratory volume and forced vital capacity of African and Indian adults in Guyana. Am Rev Respir Dis 1970; 102:979-98 I. 5. Miller G J, Saunders M J, Gilson RJC, Ashcroft MT. Lung function of healthy boys and girls in Jamaica in
L u n g f u n c t i o n in Bangladeshi teenagers
6. 7. 8.
9. 10.
I I. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.
23. 24. 25. 26. 27. 28,
relation to ethnic composition, test exercise perfomance and habitual physical activity. Thorax 1977; 32: 486-496. Mustafa KY. Spirometric lung function tests in normal men of African ethnic origin. Am Rev Respir Dis 1977; 116: 209-213. Jain SK, Ramiah TJ. Prediction ofventilatory 'norms' in healthy boys 7-14 years age. Indian J Chest Dis 1967: 10: 69. Jain SK, Ramiah TJ. Normal standards of pulmonary function tests for healthy Indian men 15-40 years old. Comparison of different regression equations (prediction formulae). Indian J M e d R e s 1969: 57: 1453-1463. Meenaxmi K, Singh HD. Lung function in school boys. lndian J Physiol Pharmaco11971: 15(2): 19. Verma SS, Kishore N, Raman CV, Lakhera SC, Das SK. Prediction of some ventilatory 'norms' in healthy Indian males of 21-69 years age. Indian J Physiol Pharmacol 1983: 27: 45-49. Udwadia FE, Sunavala JD, Shetye VM, Jain PK. The maximal expiratory flow-volume curve in normal subjects in India. Chest 1986: 89: 852-856. Chatterjee S, Saha D, Chatterjee BP. Pulmonary funtion studies in healthy non-smoking men of Calcutta. Ann Hum Bio11988; 15: 365-374. Malik MA, Moss E, Lee WR. Prediction values for the ventilatory capacity in male West Pakistani workers in United Kingdom. Thorax 1972; 27:611-619. Williams DE, Miller RD, Taylor WF. Pulmonary function studies in healthy Pakistani adults. Thorax 1978; 37: 243-249. Ayub M, Zaidi SH, Burki NK. spirometry and flowvolume curves in healthy, normal Pakistanis. Brit J Dis Chest 1987: 81: 35-43. Bhattacharya AK, Banerjee S. Vital capital in children and young adults in India. lndian J Med Res 1966; 54: 62-71. Bhatia SL. The vital capacity of the lungs, lndian Med Gazette 1929; 04: 519-521. Sobol T, Read J. Maximal expiratory flow rates in Australian adults. Aust Ann Med 1961; 10: 49-51. Laszlo G. Standardised lung function testing. Thorax 1984; 39: 881-889. American Thoracic Society: Standardization of spirometry 1987 update. Am Rev Respir Dis 1987; 136: 1285-1298. Weiner JS, Lourice JA. Human Biology--A Guide to Field Methods Oxford: Blackwell Science Publishers 1969. Melia RJW, Swan AV, Clarke G, Florey C du Ve, Nelson AN. Technical note: Suitability of a new turbine spirometer for epidemiological surveys in children. Bull Eur Physiopath Resph- 1985; 21: 43-48. Chowenczyk P J, Lawson CP. Pocket-sized device for measuring forced expiratory volume in one second and forced vital capacity. Brit M e d J 1982; 285: 15-17. Gunawardena RA, Houston K, Smith AP. Evaluation of the turbine pocket spirometer. Thorax 1987; 42: 689-693. Fairnbairn AS, Wood CM, Fletcher CM. Variability in answers to a questionnaire on respiratory symptoms. Br JPrev Soc Med 1959; 13: 175-193. Townsend MC. Spirometric forced expiratory volumes measured in the standing versus the sitting posture. A M Rev Respir Dis 1984; 130: 123-124. De P and De BN. The vital capacity of the Bangalees. Indian MedGazette 1939; 74: 409-414. Mukherjee HN, Gupta PC. The basal metabolism of Indians (Bengalees). Indian J Med Res 1931; 18: 807.
55
29. Strang LB. The ventilatory capacity of normal children. Thorax 1959; 14: 305-310. 30. Leeder SR, Swan AV, Peat JK, Woodclock AJ, Blackburn CRB. Maximum expiratory flow volume-curves in children: changes with growth and individual variability. Bull Eur Physiopath Respir 1977; 13: 249-260. 31. Taussig LM. Maximal expiratory flows at functional residual capacity: a test of lung function for young children. A M Rev Respir Dis 1977; 116:1331-1338. 32a Tanner JM, Whitehouse RH, Takaishi M. Standards from birth to maturity for height, weight and height velocity and weight velocity; British chidren, 1965. Arch Dis Child 1966; 41: 454--471. 32bTanner JM, Whitehouse RH, Takaishi M. Standards from birth to maturity for height, weight and height velocity and weight velocity; British chidren, 1965. Arch Dis Child 1966; 41: 613-635. 33. Tanner JM, Whitehouse RH. Clinical longitudinal standards for height, weight and height velocity and weight velocity and the stages of puberty. Arch Dis Child 1976; 51: 170-179. 34. Tanner JM. Human Growth (F Falkner, J Tanner, eds) 2nd ed, London: Plenum Press, 1986. 35. Tanner JM. Puberty, In: Foetus into Man London: Open books, 1978; 69 pp. 36. Primhak R_A,Biggins JD, Tsanakas JN, Hatzimiehael A, Milner RDG, Karpouzas JG. Factors affecting the peak expiratory flow rates in children. Br JDis Chest 1984; 78: 26-35. 37. Koch G. Standardization of lung function testing in infants, children and adolescents. Bull Europ Physiopath Respir 1983; 19: 15-24. 38. Godfrey S, Kamburoff PL, Nairn JN. Spirometry, lung volumes and airway resistance in normal children aged 5-18 years. Br JDis Chest 1970; 64: 15-24. 39. Gupta CK, Mather N. Statistical model relating peak expiratory flow rates to age, height and weight in men and women. JEpidemiol Commun Hlth 1982; 36: 64-67. 40. Myers JA. Vital Capacity of the Lungs Baltimore, Maryland: Williams and Wilkins Company, 1925; pp, 32-35. 41. Bhargava RP, Misra SM, Gupta NK. Ventilatory tests and lung volume studies in Madhya Pradesh-Physiological norms. Indian J Physiol Pharmacol 1973; 17: 267-272. 42. Talsania RC, Phadia EG, Goel TP. Vital capacity and maximum breathing capacity in Gujrathis. Indian J Physiol Pharmaco11965; 9: 67-74. 43. Kamat SR, Tyahi NK, Rashid SSA. Lung function in Indian adult subjects. Lunglndia 1982; 1:11-21. 44. Patrick JM, Patel A. Ethnic differences in the growth of lung function in children. Ann Hum BioI 1986; 13: 307-315. 45. Polgar G, Promadhat V. Pulmonary Function Testing in Children: Techniques and Standards. Philadelphia: W.B. Saunders Co, 1971 46. Sliman NA, Dajani BM, Shubair KS. Pulmonary function in normal Jordanian children. Thorax 1982; 37: 854--857. 47. Lain KK, Pang SC, Allan WGL et al., Predictive nomograms for forced expiratory volume, forced vital capacity and peak expiratory flow rate in Chinese adults and children. Brit J Dis Chest 1983; 77: 390-396. 48. Shamssain MH, Thompson J, Ogston SA. Forced expiratory indices in normal Libyan children aged 6-19 years. Thorax 1988; 43: 467-470.