Comparison of fourth and fifth Korotkoff diastolic blood pressures in 5 to 30 year old individuals

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1995; 8:1083-1089

Comparison of Fourth and Fifth Korotkoff Diastolic Blood Pressures in 5 to 30 Year Old Individuals The Bogalusa Heart Study Isaac W. Hammond, Elaine M. Urbina, Wendy A. Wattigney, Weihang Bao, William C. Steinmann, and Gerald S.Berenson

The use of fourth phase Korotkoff sound (K4) versus fifth phase Korotkoff sound (K5) for the determination of diastolic blood pressure (DBP) has been a subject of controversy since the indirect method of determining arterial blood pressure was described. Using data from the Bogalusa Heart Study, we evaluated the differences between K4 and K5 (K4 - K5) from 4633 subjects 5 to 30 years of age examined b e t w e e n 1987 and 1991. The overall mean difference between K4 and K5 was 9.9 ± 5.6 mm Hg (mean ± SD). The average difference was highest in 5 to 8 year olds, where it measured 12.3 ± 5.5 mm Hg. The average K4-K5 difference fell with increasing age and reached a value of 6.3 ± 2.6 mm Hg by 25 years of age. For all race/sex groups, the youngest two age groups differed statistically from the oldest age groups in K4-K5 difference (P K .006). There were significant differ-

KEY WORDS: Blood pressure measurement, diastolic blood pressure, Korotkoff sounds, Bogalusa Heart Study.

Received December 8, 1994. Accepted May 23, 1995. From the Tulane Center for Cardiovascular Health, Tulane School of Public Health & Tropical Medicine (WAW, WB, GSB); and the Departments of Medicine (1WH, WCS) and Pediatrics (Cardiology) (EMU), Tulane University Medical Center; New Orleans, Louisiana. This research is supported by funds from the National Heart, Lung, and Blood institute of the U.S. Public Health Service (USPHS), Early Natural History of Arteriosclerosis HL38844. Address correspondence and reprint requests to Gerald S. Berenson, MD, Tulane Center for Cardiovascular Health, Tulane School of Public Health & Tropical Medicine, 1501 Canal Street, 14th Floor, New Orleans, LA 70112-2824.

ypertension is one of the most important risk factors for death in the United States. Although indirect measurement of blood pressure by s p h y g m o m a n o m e t e r is routine for detection and monitoring of hypertension, there are limitations to the m et hod and its interpretation. The Korotkoff phases or sounds are used to determine systolic and diastolic blood pressures. Systolic blood pressure is denoted by the first phase (the first appearance of faint, clear tapping sounds that

~ 1995 by the American ]oltr~zal o! H~/~crtc!Isi~z I ~d

ences between blacks and whites (P < .015) and between men and w om en ( P < .001) for subjects between 13 and 17 years of age. Additional analyses were performed with individuals having K5 = 0 added to yield an expanded popul at i on of 5117 persons. Overall, 9.5% had at least one of six measurements of K5 = 0 and most were y o u n g subjects: 27% of children 5 to 8 years and 13% of children 9 to 12 years. We conclude that by age 15 there may be no relevant clinical difference in K4K5. However, in children, K4 and K5 should be recorded and K4 is a more reproducible measure of diastolic blood pressure. Am J Hypertens 1995;8: 1083-1089

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0895-7061/95/$9.50 0895-7061 (95)00230-M

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gradually increase in intensity). Diastolic blood pressure is denoted by the fourth phase (when there is muffling of sound so that a soft, blowing quality is heard) or the fifth phase (when sound disappears). The choice of fourth versus fifth phase has been controversial as long as the indirect method of determining blood pressure has been in use. Standards for the determination of blood pressure were established in 1939 by a committee that recommended the fourth phase be used for diastolic blood pressure. 1 In 1951 the recommendations were revised and the fifth phase was recommended as diastolic blood pressure. 2 By 1967 the World Health Organization and the American Heart Association both recommended that both the fourth and fifth phases be recorded. 3'4 The controversy over blood pressure measurements has continued, especially for children, since recommendations are to use disappearance of sound as a clear measurement in adults while in children, the disappearance of sound may occur at a pressure near zero.

More recently, observations made in population studies of children have suggested the fourth phase as a more appropriate measurement, s'6 Since blood pressure measurements have been obtained over a range of age from childhood to young adulthood in a relatively large biracial (black-white) population in the Bogalusa Heart Study, a comparison of fifth versus fourth phase diastolic blood pressure measurements was made to evaluate which measure of diastolic blood pressure might be more appropriate. METHODS AND MATERIALS Population The Bogalusa Heart Study is a longterm epidemiologic study of cardiovascular disease risk factors from birth through early adulthood. The study sample was selected from the children residing in Ward 4 of Washington Parish (County), LA, which includes the city of Bogalusa. This biracial community of approximately 22,000 people is two-thirds white and one-third black. Blood pressure measurements, various laborato~ measurements, a family history/ health habit questionnaire, and anthropometric data were collected on 5117 participants aged 5 to 30 years old during cross-sectional surveys from September 1987 until October 1991, according to protocols previously defined. 7'8 Blood Pressure Measurement The screening protocol began with measurement of the right upper arm length using an anthropometric caliper. This value was divided in two and the halfway point was marked on the arm. The right upper arm circumference was measured at the mark, to the nearest 1/10th cm using a cloth tape measure. Proper blood pressure cuff size was selected from a table listing cuff size as

AJH-NOVEMBER 1995-VOL. 8, NO. 11

a function of right upper arm length versus midarm circumference as developed in previously published protocols. 7'8 Replicated casual blood pressures were measured, adhering to a protocol used in all Bogalusa Heart Study examinations. 7 These were obtained by trained examiners on seated, relaxed subjects at the last stage of the screening. Six blood pressure values were recorded for each participant with mercury sphygmomanometers (W.A. Baum Co., Inc., Copague, NY). Blood pressures were recorded as the first, fourth, and fifth Korotkoff phases. The mean of the six blood pressures was used in the analyses. Upon completion of the screening, reexamination and blood pressure recordings were repeated on a 10% random sample of the study subjects for quality control. Subjects with a fifth phase diastolic blood pressure recording of 0 mm Hg (N = 484) were removed from the initial analyses, since averaging these values would artificially skew the data. This yields a total study population of 4633. However, additional analyses were performed on an expanded study population (N = 5117) that included individuals with a fifth phase diastolic blood pressure of zero. The percent distribution by age and race/sex group for subjects with a fifth phase diastolic blood pressure reading of zero for one or more of the six manual blood pressures recorded during the screening process was then determined. Statistical Analysis The Statistical Analysis System (SAS Inc., Cary, NC) was used for the analyses. 9 Descriptive statistics were used to describe the mean systolic (SBP), diastolic fourth phase (K4), diastolic fifth phase blood pressures (K5), and the difference between the fourth and fifth phase diastolic blood pressures (K4 - K5) of the study cohort. Student's t test for paired dependent means was used to test the difference between the two measures of diastolic blood pressure. To test the distribution of the difference between the two diastolic blood pressure measures, the ×2 test for the goodness of fit was used. RESULTS The study population ranged in age from 5 to 30 years with a mean age of 17.1 -+ 7.6 years. Forty-seven percent of these subjects were men, and 63% percent were white. The average blood pressure (SBP/K4/K5) for the population was 105.4/65.2/55.2 mm Hg --- 11.7/ 10.2/13.3 mm Hg. The mean difference between the fourth and fifth phase Korotkoff diastolic blood pressures (K4 - K5) was 9.9 -+ 5.6 mm Hg (Table 1). When examining the magnitude of the difference between fourth and fifth phase DBP, it was found that 18 (0.40%) subjects had no difference between the fourth and fifth phase DBP, 660 (14.2%) subjects

DIASTOLIC BLOOD PRESSURE COMPARISON 1085

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TABLE 1. BLOOD PRESSURE LEVELS AND NUMBER OF CHILDREN AND YOUNG ADULTS EXAMINED FOR INDIRECT BLOOD PRESSURE BY AGE Age (years)

No.

5-8 9-12 13-17 18-24 25-30 Total

800 964 981 855 1033 4633*

Diastolic Blood Pressure --K4 K5

Systolic Blood Pressure

93.8 100.3 108.7 110.8 111.5 105.4

z 8.1 -+ 8.9 +- 9.7 Jr 10.0 +_ 10.6 +- 11.7

54.4 61.2 66.2 69.7 72.5 65.2

+ 7.9 -+ 8.2 -+ 7.4 +- 7.9 +- 8.6 +- 10.2

42.2 48.1 55.4 62.2 66.2 55.2

+ 9.9 -_ 11.1 +-_ 10.4 -~ 9.4 -+ 9.4 -+ 13.3

Average K4 - K5 Difference

12.3 13.1 10.8 7.5 6.3 9.9

+ 5.5 + 6.3 -+ 5.5 - 3.5 + 2.6 + 5.6

Subjects with K5 = 0 excluded. Blood pressures given as mean +- SD m mm Hg. Population: 47% men, 63~>'~white: mea~i a~e 17.l +- 7.~ years.

h a d a difference of I to 4 m m H g b e t w e e n fourth and fifth p h a s e s , 1,777 (38.4%) h a d a difference of 5 to 8 m m Hg, 1059 (22.9%) subjects h a d a difference of 9 to 12 m m Hg, 554 (12.0%) subjects h a d a difference of 13 to 16 m m Hg, a n d 565 (12.2~) subjects had a difference of 17 m m H g or m o r e . The p e r c e n t distribution of the K4-K5 difference w a s also e x a m i n e d b y age (Figure 1). There is a trend for d e c r e a s e d differences b e t w e e n fourth a n d fifth p h a s e DBP w i t h increasing age. A ×2 analysis re ~ vealed significant differences b e t w e e n the age g r o u p s (×2 = 1244.2, P < .001). W h e n the percent distribution of the K4-K5 difference w a s e x a m i n e d by age, race, a n d sex g r o u p s (Figure 2), the trend for decreased differences b e t w e e n fourth a n d fifth p h a s e DBP with increasing age w a s again seen. For all race/ sex g r o u p s , the y o u n g e s t t w o age g r o u p s (5 to 8 years old a n d 9 to 12 years old) differed statistically from t h e oldest age g r o u p s (18 to 24 years old a n d 25 to 30 y e a r s old) in K4-K5 differences (P < .006). Within

each age range, there are no differences b e t w e e n a n y of the four race/sex g r o u p s , except for subjects 13 to 17 years of age w h e r e all four g r o u p s differed significantly (P K .015). Similarly, in a g i v e n age g r o u p , there w e r e only statistically significant differences bet w e e n blacks a n d whites (P < .015) a n d b e t w e e n m e n a n d w o m e n (P < .001) for subjects b e t w e e n 13 a n d 17 years of age. Univariate correlation coefficients w e r e d e r i v e d bet w e e n the different b l o o d p r e s s u r e p a r a m e t e r s (Table 2). Systolic blood p r e s s u r e w a s positively correlated with b o t h fourth a n d fifth p h a s e b l o o d p r e s s u r e s a n d this effect w a s still significant after correction for age. The correlations b e t w e e n K1, K4, K5, a n d t h e K4-K5 d i f f e r e n c e w e r e all n e g a t i v e . H o w e v e r , after correction for age, systolic b l o o d p r e s s u r e h a d a w e a k l y positive correlation w i t h K4-K5 difference (all P < .001). Correlations w e r e also derived b e t w e e n b l o o d pressure p a r a m e t e r s a n d selected a n t h r o p o m e t r i c vari-

60 5O 0 • ..Q ::3 0rJ

Age (years) 40

m5-8 ~9-12

30

•13-17 O 1._

D.

E~ 18-24

20

m25-30 10

N =4633

1-4

5-8

9-12

13-16

K4-K5 Difference (mmHg) (X 2 =

1244

P <

0001)

>17

FIGURE 1.

The percent distribution of children and young adults with differences of diastolic blood pressure (K4 - K5) by age. Note at younger ages considerably greater differences are found.

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14 r

A

03 "1"

E

v

HAMMOND ET AL

E o o c oI . =

12 10

! Race/Sex Group mWhite Males

8

EZ]White Females 6

~ B l a c k Males

I,I-.m

a

4

4-

2

U3 Back Females N=4633

0

5-8

9-12

13-17

18-24

FIGURE 2. The difference between diastolic blood pressure measurements of K4 and K5 with increasing age by race and sex groups. A t adolescence significant differences were found between men and women. Also decreasing differences are notes after adult stature is reached.

25-30

Age (years) (For all groups, Age, Race: P< .001) (*Sex: P< 001)

ables (Table 2). Age, weight, height, and body mass index were all strongly positive correlates of K1, K4, and KS, and these effects persisted, although to a lesser degree, after a d j u s t m e n t for age. These anthropometric variables were weakly, and negatively, correlated with the K4-K5 difference; however, after adj u s t m e n t for age, a n t h r o p o m e t r i c observations were weakly, t h o u g h significantly, positively correlated with the K4-K5 difference (all P < .001). Additional analyses were p e r f o r m e d with those individuals having a fifth phase diastolic blood pressure recording of zero to 20 m m Hg (N = 484) a d d e d to the s t u d y p o p u l a t i o n to yield an e x p a n d e d population of 5117 subjects, Overall, 9.5% of the total population had at least one fifth phase diastolic blood pressure m e a s u r e m e n t of zero. Most of these subjects were y o u n g , in fact, almost one-third (27.5~) of all children aged 5 to 8 vears had at least one fifth phase diastolic blood pressure m e a s u r e m e n t of zero. The percentage of children with a K5 of zero was still significant in the 9 to 12 year age g r o u p (13~7~) but by adolescence, this percentage had fallen to a negligible a m o u n t (0.03%). The percent distributions by age, race, and sex g r o u p of subjects with a fifth phase blood pressure of zero was also d e t e r m i n e d and is s h o w n in Figure 3.

DISCUSSION A l t h o u g h the d i l e m m a of w h e t h e r f o u r t h or fifth phase diastolic blood pressure is the most appropriate measure of diastolic blood pressure remains, 1°'11 data resulting from adult e p i d e m i o l o g y studies continue to r e c o m m e n d the fifth phase. 12 W h e t h e r this r e c o m m e n d a t i o n s h o u l d be e x t r a p o l a t e d to b l o o d pressure m e a s u r e m e n t s in children based o n adult experiences is not settled. In our initial observations to develop m e t h o d s of recording blood p r e s s u r e in children it was n o t e d that muffling of the f o u r t h phase was a clearer characteristic than n o t i n g a precise level of s o u n d disappearance (fifth phase). 5 Further, a significant n u m b e r of m e a s u r e m e n t s o n children were n o t e d not to have a clear fifth phase, with s o u n d s persisting to very low levels a n d often to zero. Few direct arterial and indirect studies have b e e n p e r f o r m e d in children. In 1963, in a s t u d y of 120 children u n d e r g o i n g diagnostic cardiac catheterization for congenital heart disease, Moss et al f o u n d that indirectly m e a s u r e d K4 slightly o v e r e s t i m a t e d intraarterial diastolic blood pressure a n d K5 underestimated to an even greater degree. 13 H o w e v e r , since similar large studies have not b e e n c o n d u c t e d on

TABLE 2. AGE ADJUSTED UNIVARIATE CORRELATION COEFFICIENTS BETWEEN SELECTED VARIABLES

SBP K4 K5 K4 - K5

SBP

K4

1 0.62 0.43 0.14

0.62 1 0.88 0.15

All P < .0001. N = 4633.

K5

K4 - K5

Weight

Height

Body Mass Index

0.43 0.88 1 -0.6

0.14 - 0.15 -0.6 1

0.43 0.3 0.23 0.02

0.4 0.29 0.2 0.06

0.34 0.25 0.19 0.02

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DIASTOLIC BLOOD PRESSURE COMPARISON

1087

3O

,~.

25

•~,

20

I Race/Sex Groups iWhite

Male

E~White Female

p 15

I l l Black Male

o a.

E-J Black Female

10

FIGURE 3. The percent distribution of subjects with K5 diastolic blood pressure at O. Note the greater percent in the childhood age groups.

N=5117 i

5-8

9-12

13-17

18-24

25-30

Age (years) *At/east one of six readings taken by 2 observers is zero

healthy children, it remains unclear which measure is truly the better estimate of diastolic blood pressure in children. 1° Consequently, the recording of both fourth and fifth phases has been routine in the Bogalusa Heart Study; this is also recommended by the American Heart Association. t4 For children, observations in Bogalusa provide an opportunity to examine both measures more extensively. Analyses in children have used averages of fourth phase measurements in most instances because of the difficulty with measurement of the fifth phase. Analysis of tracking further indicates fourth phase mav~ be more predictive of a future diastolic pressure. 1~'~6 The current data studying differences between K4 and K5 over various age groups show that the difference between the fourth and fifth phase diastolic blood pressure decreases with age. Therefore, fifth phase measurements may be appropriate after children reach adult stature and blood pressure levels tend to reach a plateau. However, for measurements in childhood and adolescence, perhaps up to age 15 to 18 years, fourth phase is recommended from our data. Figure 3 suggests an earlier age may be appropriate in girls since mature stature is reached earlier. Although race and gender differences in blood pressure may exist, 7'17'18 the difference between fourth and fifth phase diastolic blood pressure appears to be most influenced by age or size of the individual. 19 Only during the age range when puberty is expected to occur do significant race or sex differences in K4-K5 appear. This might be explained by the differences in age at which puberty and therefore, growth spurt, occurs between the four race/sex groups. The hypothesis that growth may influence the K4-K5 difference is suggested by data that shows body size expressed as height or ponderal index

(weight/height3) is a strong correlate of blood pressure in growing children. 19 However, anthropometric measurements were only weakly correlated with the K4-K5 differences in this study. Therefore, other physiologic factors may be influencing the change of the K4-K5 difference with age, such as changes in arterial elasticity. 13 A high percentage of children will have at least one fifth phase measurement of zero. Observations of indirect blood pressure being made by automatic instruments may not clarify this decision since some instruments tend to measure diastolic blood pressure higher at y o u n g ages a n d lower after adolescence. 2°'21 Furthermore, if an automatic oscillometric type instrument is employed, the systolic and mean blood pressure will be measured and both and diastolic blood pressure is calculated. Two trends were observed in these data. First there was a bigger difference between fourth and fifth phase DBP noted in younger children at lower blood pressures and a higher percentage of younger children had at least one fifth phase recording of zero. This will tend to minimize the significance of any systematic K4-K5 difference that might exist in the data and thus their clinical significance. The trend towards decreasing K4 - K5 with age has been described previously in the literature 22"23 and the clarity of the fourth versus the fifth phase is said to be more distinct in children than in adults. 1° Furthermore, the fourth Korotkoff sound is the more clearly distinguished phase in children as compared to adults where K5 is being recommended. 11 Differences noted in our studies are consistent with the absolute differences reported by Folsom et al, 22 although those observations were on subjects between 24 and 75 years. Similarly, Hense et a123 re-

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p o r t e d that 38.2% h a d no absolute difference bet w e e n fourth a n d fifth p h a s e in his s t u d y including individuals with an a v e r a g e of 48 years (range 30 to 60 years) c o m p a r e d to our 0.4% in the p r e s e n t study. In one of the few reports on the K4-K5 difference in children, Sinaiko f o u n d that half of the M i n n e s o t a children studied h a d no difference b e t w e e n K4 a n d K5. 6 H o w e v e r , only t w o m e a s u r e m e n t s w e r e perf o r m e d a n d 57.6% of the p o p u l a t i o n w a s 13 years of age or older, the age at w h i c h smaller K4-K5 differences are s e e n in our data as well. T h e m e a n d i f f e r e n c e b e t w e e n f o u r t h a n d fifth p h a s e DBP w a s a p p r o x i m a t e l y 10 m m Hg, consistent w i t h earlier observations. 24 C o n s i d e r a t i o n of this difference could influence decisions to treat high blood p r e s s u r e . For e x a m p l e , a case with persistent BP of 138/96/86, w o u l d be c o n s i d e r e d n o r m o t e n s i v e b a s e d on a specific cutpoint, 140/90. If we use fourth p h a s e the patient m a y be c o n s i d e r e d to h a v e h y p e r t e n s i o n . We note f r o m our a u t o p s y studies a n d echocardiographic o b s e r v a t i o n s evidence of cardiac e n l a r g e m e n t a n d renal artery c h a n g e s occur at m u c h lower levels t h a n criteria for a b n o r m a l i t y in adults. At the 90th percentile for the fourth phase, evidence of target o r g a n c h a n g e s a r e f o u n d . 25"26 H o w e v e r there still rem a i n s c o n t r o v e r s y as to which are the m o s t a p p r o priate diastolic blood p r e s s u r e percentiles b a s e d on distributions in a p o p u l a t i o n , especially in g r o w i n g children. 19 T h e choice of K o r o t k o f f s o u n d affects decision for t h e r a p y ; c o n s e q u e n t l y the choice should rest on the e x t e n s i v e e p i d e m i o l o g i c o b s e r v a t i o n s . Sinaiko et al c o m p a r e d results f r o m the Minnesota-St. Paul Children a n d A d o l e s c e n t Blood Pressure Prog r a m to the 1987 Task Force Report on Blood Pressure Control in Children. 6'11 He f o u n d that the p r e v a l e n c e of s i g n i f i c a n t diastolic h y p e r t e n s i o n w a s u n d e r e s t i m a t e d b y 2% to 3% if K5 rather t h a n K4 w a s used. 6 Fortunately, the difference b e t w e e n K4 and K5 decreases f r o m a m e a n of 12 m m H g to approxim a t e l y 6 m m H g in m e a s u r e m e n t s f r o m age 5 years to 30 years. In an adult p o p u l a t i o n , the K4-K5 difference m a y h a v e less clinical relevance to h y p e r t e n s i v e diseases. In contrast to adults, there are significant differences b e t w e e n fourth a n d fifth p h a s e diastolic blood p r e s s u r e s n o t e d at y o u n g ages. A h i g h p e r c e n t a g e of children will h a v e a fifth p h a s e m e a s u r e m e n t of zero. F r o m this observation, along with better tracking of fourth p h a s e diastolic b l o o d pressure, it is s u g g e s t e d the fourth p h a s e r e m a i n s the m o r e a p p r o p r i a t e m e a sure t h r o u g h the adolescence.

AJH-NOVEMBER 1995-VOL. 8, NO. 11

REFERENCES 1. Joint recommendations of the American Heart Association and the Cardiac Society of Great Britain and Ireland: standardization of blood pressure reading. New York, American Heart Association, Inc., July 1939. 2. Committee to Revise Standardization of High Blood Pressure Readings: Recommendations for h u m a n blood pressure determinations by sphygmomanometers. New York, American Heart Association, October 1951. 3. World Health Organization Technical Report Series, No. 231, 1962 (Arterial hypertension and ischemic heart disease). 4. Report of a Subcommittee of the Postgraduate Education Committee, American Heart Association: Recommendation for human blood pressure determination by sphygmomanometers. Circulation 1967;36:980-988. 5. Voors AW, Weber LS, Berenson GS: A choice of diastolic Korotkoff phases in mercury sphygmomanometry of children. Prey Med 1979;8:492-499. 6.

Sinaiko AR, Gomez-Marin O, Prineas RJ: Diastolic fourth and fifth phase blood pressure in 10-15-yearold children. Am J Epidemiol 1990;132:647-655.

7.

Voors AW, Foster TA, Frerichs RR, et al: Studies of Blood Pressures in Children, Ages 5-14 Years, in a Total Biracial Community, The Bogalusa Heart Study. Circulation 1976;54:319-327. 8. Berenson GS, McMahan CA, Voors AW, et al: Cardiovascular Risk Factors in Children--The Early Natural History of Atherosclerosis and Essential Hypertension. New York, Oxford University Press, 1980, p 450. 9. SAS Institute Inc.: SAS/STAT User's Guide, Version 6, 4th ed. Cary, NC, SAS Institute Inc., 1989. 10 Geddes LA: The Direct and Indirect Measurement of Blood Pressure. Chicago, Year Book Medical Publishers, Inc., 1970, pp 5-196. 11

National Heart, Lung and Blood Institute's Task Force on Blood Pressure Control in Children: Report of the Second Task Force on Blood Pressure Control in Children. Pediatrics 1987;79:1-25. 12 National High Blood Pressure Education Program Working Group report on primary prevention of hypertension. Arch Intern Med 1993;153:186-208.

13 Moss AJ, Adams FH: Index of indirect estimation of diastolic blood pressure. Am J Dis Child 1963;106:364367. 14 Perloff D, Grim C, Flack J, et al: Human blood pressure determination by sphygmomanometry. Circulation 1993;88:2460-2470. 15 Voors AW, Webber LS, Berenson GS: Time course studies of blood pressure in children--The Bogalusa Heart Study. Am J Epidemiol 1979;109:320-334.

ACKNOWLEDGMENT

16 Webber LS, Cresanta JL, Voors AW, Berenson GS: Tracking of cardiovascular disease risk factor variables in school-age children. J Chronic Dis 1983;36:647-660.

The authors express appreciation to the Bogalusa Heart Study staff, Dan Kuras for computer assistance, and the children of Bogalusa. Without their cooperation this study would not be possible.

17 Voors AW, Berenson GW, Dalferes ER, Jr.: Racial differences in blood pressure control. Science 1979;204: 1091-1094. 18 Berenson GS, Webber LS, Srinivasan SR: Pathogenesis

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of hypertension in black and white children. Proceedings of the Second International Interdisciplinary Conference on Hypertension. Clin Cardiol 1989;12(suppl IV):IV3-IV8.

DIASTOLIC BLOOD PRESSURE COMPARISON 1089

differences between fourth and fifth phase diastolic blood pressures in 4885 adults: implications for blood pressure surveys. Int J Epidemiol 1984;13(4):436 441.

20 Voors AW, Sklov MC, Halperin H, et al: Comparison of two automatic blood pressure recorders and the mercury sphygmomanometer. Hypertension 1982;4: 329-336.

23 Hense HW, Stieber J, Chambers L: Factors associated with measured differences between fourth and fifth phase diastolic blood pressure. Int J Epidemiol 1986;15(4):513-518. 24. D'Souza MF, Irwig LM: Measurement of blood pressure. Br Med J 1976;4:814-815. 25 Newman WP, Ill, Freedman DS, Srinivasan SR, Berenson GS: Risk factors in children and early atherosclerosis. N Engl J Med 1986;314:1580.

21 Wattigney WA, Webber LS, Lawrence MD, Berenson GS: Utility of an automatic instrument for blood pressure measurements in children. The Bogalusa Heart Study. Hypertension (Submitted).

26 Daniels SR, Meyer RA, Strife CF, et al: Distribution of target-organ abnormalities by race and sex in children with essential hypertension. J Human Hypertens 1990;4:103-104.

19 Voors AW, Webber LS, Frerichs RR, Berenson GS: Body height and body mass as determinants of basal blood pressure in children--The Bogalusa Heart Study. Am J Epidemiol 1977;106:101-108.

22 Folsom AR, Prineas RJ, Jacobs DR, et al: Measured