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Diabetes in Ghana: a community based prevalence study in Greater Accra
Diabetes Research and Clinical Practice 56 (2002) 197– 205 www.elsevier.com/locate/diabres
Diabetes in Ghana: a community based prevalence study in Greater Accra Albert G.B. Amoah a,b,*, Samuel K. Owusu a,b, Samuel Adjei c a
Department of Medicine and Therapeutics, Diabetes Research Laboratory, Uni6ersity of Ghana Medical School, P.O. Box 4236, Accra, Ghana b National Diabetes Management and Research Centre, Korle Bu Teaching Hospital, Accra, Ghana c Health Research Unit, Ministry of Health, Accra, Ghana Received 15 March 2001; received in revised form 24 November 2001; accepted 4 December 2001
Abstract Data on the prevalence of diabetes in Ghana is scanty and unreliable. In the present study we have ascertained the prevalence of diabetes, impaired fasting glycaemia (IFG) and impaired glucose tolerance (IGT) in a random cluster sample of Ghanaians aged 25 years and above from the Greater Accra area of Ghana. Diabetes, IFG and IGT were defined by criteria of the American Diabetes Association and World Health Organization. The mean age of the 4733 subjects involved in the study was 44.3 9 14.7 years, and participation rate was 75%. The crude prevalence of diabetes was 6.3%. Out of 300 subjects with diabetes, 209 (69.7%) had no prior history of the disease. Diabetes, IGT and combined IFG and IGT increased with age. The oldest age group (64 + years) had the highest diabetes prevalence (13.6%). The age-adjusted prevalence of diabetes, IFG and IGT, were 6.4, 6.0 and 10.7%, respectively. Diabetes was more common in males than females (7.7 vs. 5.5%) [PB 0.05]. Worsening glycaemic status tended to be associated with increase in age, body mass index, systolic and diastolic blood pressures. Ascertainment of predictors for diabetes in Ghanaians and the significance of the relatively high rates of and IFG and IGT however, remain to be determined. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Type 2 diabetes; Prevalence; Impaired fasting glycaemia; Impaired glucose tolerance; Ghana
1. Introduction The prevalence of diabetes in sub-Saharan Africa had been estimated between 0.0 and 1.9% [1 – 12]. Recent studies from urban Cameroon, Nigeria and Tanzania suggest that the disease may now be more common in sub-Saharan Africa than previously * Corresponding author. Tel./fax: +233-21-67-1047. E-mail address: [email protected] (A.G.B. Amoah).
thought [12 –14]. In Ghana, information on the prevalence of diabetes is scanty and outdated. In 1958, using urinalysis for diabetes screening, Dodu [1] found a diabetes prevalence of 0.4% among 4000 urban outpatient population in Accra. In a community sample of 5000 subjects from a provincial capital in Ghana, Dodu and de Heer [15] reported a diabetes prevalence of 0.2%. Based on these figures, the impression was created among policy makers that diabetes is rare in Ghanaians.
0168-8227/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 1 6 8 - 8 2 2 7 ( 0 1 ) 0 0 3 7 4 - 6
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The diagnostic criteria for diabetes have recently been revised by an Expert Committee of the American Diabetes Association (ADA) [16] and by a World Health Organization (WHO) consultation [17]. The threshold of fasting plasma glucose for diabetes has been lowered to 7.0 mmol/l and an additional category, impaired fasting glycaemia (IFG) has been proposed as a new group with increased risk of developing diabetes [16,17]. Additionally, the WHO retained the 2-h glucose criteria for diagnosis of diabetes [17]. The new diagnostic criteria have recently been employed to review previously published studies in Africans [18]. Ghana is a tropical country in West Africa with a surface area of 238,533 km2. The population in 2000 was 19.7 million with a gross domestic product (GDP) of US$ 7.4 bn and per capita GDP of US$ 412. The Accra metropolitan area is the largest urban population (1.6 million) [19]. In 1998, a non-communicable diseases survey (NCDS 98) was initiated to determine the prevalence of diabetes, hypertension, obesity, ischaemic heart disease and cardiovascular risk factors in selected communities in this area. In this communication, we report the prevalence of diabetes, IFG and IGT in the Greater Accra area, using the new diagnostic criteria [16,17].
2. Patients and methods
2.1. Target population and sampling For ease of survey, two urban communities in the Accra metropolis (Labadi/Cantoments and Teshie), together with one area of rural Accra (Danfa/Abokobi, 20 villages) were selected as representative. A stratified two-stage cluster sampling technique was used. A sample size of 752 was determined based on an estimate of diabetes prevalence of 2%, an absolute precision of 1% and a confidence interval of 95%, in accordance with the Statcalc function of Epi Info, Version 6 (Center for Diseases Control, Atlanta, Georgia, USA, and World Health Organization, Geneva, Switzerland). This sample size was multiplied by the maximum design effect
for clustering of two to give a sample of 1504. To allow for a non-response rate of 20% and nonparticipation rate of 10%, a final sample size of 2100 per community was employed. The Ghana Statistical Service randomly selected 14 census enumeration zones from each of the two urban communities. From each zone, adults aged ] 25 years were listed, and 150 eligible subjects were subsequently selected by systematic random sampling per enumeration area to participate in the study. In the rural area, all eligible adults were listed and randomized. From each of the three survey communities, 2100 subjects were recruited into the study.
2.2. Sur6ey personal A 19-member team made up of a graduate field coordinator, three senior public health nurses, one state registered nurse, three university graduates and 11 pre-university students were trained and supervised to perform household listing by the Ghana Statistical Service. Five laboratory technicians, one phlebotomist, four additional senior public health nurses, one community health nurse and two pre-university students were subsequently recruited to join 17 members of the original census team for the actual survey. To standardize survey measurements and procedures, the survey team was trained using specially prepared survey manuals that conformed to recommended noncommunicable disease survey protocols [20]. Three of the senior public health nurses were trained and certified to measure blood pressure accurately, using a double headed stethoscope and resource material from Shared Care (Accurate blood pressure measurement, a video course. Torrance, CA, USA).
2.3. Sur6ey methods Fasting blood samples was taken from subjects before 10:00 h. Subjects then drank the equivalent of 75 g of anhydrous glucose in 300 ml of water and a second blood sample was taken 2 h after the glucose drink. During the OGTT, subjects did not engage in strenuous activity or smoke. Fluoridated blood samples were kept on ice and cen-
A.G.B. Amoah et al. / Diabetes Research and Clinical Practice 56 (2002) 197–205
trifuged within 15 min. The resultant plasma was frozen on dry ice in the field and transported frozen to be stored at − 80° C until analyzed. Plasma glucose was determined with glucose oxidase kits (Randox Laboratories Ltd., Crumlin, UK) on an automatic chemistry analyzer (Erba Smartlab, Mumbai, India) at the Diabetes Research Laboratory of the University of Ghana Medical School, Accra. Anthropometric measurements were performed on subjects in light clothing and without shoes. Weight was measured with a heavy duty Seca 770 floor digital scale (Hamburg, Germany) to the nearest 0.1 kg. Height was measured with a height measure to the nearest millimetre. Body mass index (BMI) was calculated from the weight and height measurements. After at least 10 min rest, blood pressure was measured to the nearest 2 mmHg, in the right arm of seated subjects on two occasions at an interval of 1 min with a mercury sphygmomanometer and a cuff of appropriate size. Demographic data and information on diabetes status/treatment were subsequently determined with the aid of a structured questionnaire. After the survey, demographic data were also obtained from 558 randomly selected non-respondents from the survey communities.
2.4. Sur6ey facilitation and quality assurance Before the main survey, a field trial was conducted. This involved 60 subjects from outside the three survey communities. The field trial enabled fine-tuning of survey procedures and measurements. Before and during the survey period, local resource personnel went round the community in mobile vans equipped with public address systems, each evening (18:00 h) and morning (05:00 h), to remind survey subjects to prepare correctly for the survey and to report at the survey site on time. The local resource personnel also visited scheduled participants in their homes each evening to remind them to fast correctly and report to the survey site on time. In Teshie and to a greater extent in the rural Accra, survey subjects were bussed to the survey site each morning
199
to ensure they did not have to walk long distances and to help them arrive on time. To ensure the accuracy of BP readings, the three nurses certified to measure blood pressure were re-certified every 3 weeks during the 12week survey period, using the video. The weighing scale was checked against two reference scales each morning before commencement of weighing. Finally, data collection instruments were checked for accuracy and completeness of entries before subjects were discharged home from the survey site. Plasma glucose was determined in duplicate and normal and elevated commercial control sera were run with a batch of samples from 20 subjects. The inter-assay coefficient of variation for normal and elevated plasma glucose controls was 1.4 and 2.4%, respectively, the corresponding intra-assay coefficient of variation was 1.8 and 1.4%, respectively.
2.5. Data analysis Data from the three communities were pooled together for the present report. Impaired fasting and oral glucose tolerance was defined in accordance with the new American Diabetes Association and World Health Organization criteria [16,17]. Diabetes was defined by a venous fasting plasma glucose of ] 7.0 mmol/l and/or 2-h venous plasma glucose of ]11.1 mmol/l [16,17] or treatment for diabetes (diet, oral glucose-lowering drug and/or insulin). Impaired glucose tolerance (IGT) [2-h plasma glucose 7.8–11.0 mmol/l] was ascertained in subjects without prior diabetes, whose fasting plasma glucose was B 7.0 mmol/l. Impaired fasting glycaemia (IFG) [fasting plasma glucose ]6.1 and B 7.0 mmol/l] was determined in subjects without prior diabetes, whose 2-h plasma glucose was less than 7.8 mmol/l. The statistical package SPSS 10.0 for Windows (SPSS Inc., Chicago, IL, USA) was used for analyses. Data are expressed as mean9 SD. Student’s unpaired, two-sided t-test was used to compare means between two groups and ANOVA for more than two groups. Chi-square was used in the comparison of proportions.
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Prevalence estimates were age-standardized to the Ghanaian population by the direct method [21] using a population estimate of 18.3 million and 5-year age groups from 25 years and above [22]. In addition, the prevalence estimate was age-adjusted to the ‘new’ world standard population [23].
2.6. Ethics The study was approved by the Ethical and Protocol Review Committee of the University of Ghana Medical School and complied with the Helsinki Declaration of 1975 (revised in 1983 and 1989) on human experimentation. Informed consent was obtained from all participants.
3. Results Out of a total of 6300 subjects selected, 4733 subjects participated in the study, giving a response rate of 75%. The response rates in the first, second and third communities were 70, 77 and 77%, respectively. Table 1 shows the mean9 SD of selected variables for males and females and for the total study population. The mean age of subjects was 44.39 14.7 years. Males were older and had lower BMI than females. The crude prevalence of diabetes in all subjects was 6.3%. The corresponding prevalence of IFG (n =289) and IGT (n= 502) separately were 6.1 and 10.6%, respectively. An additional 180 (3.8%) subjects had combined IFG and IGT. The crude diabetes
prevalence in the first, second and third communities were 7.3, 5.9, 5.9% (PB 0.05), respectively. Out of 300 subjects with diabetes, 209 (69.7%) had no prior history of diabetes. Diabetes was diagnosed by fasting plasma glucose alone in 65 subjects (21.7%). In 62 subjects (20.7%), diabetes was diagnosed by OGTT alone. In another 82 subjects (27.3%), both the fasting plasma glucose and OGTT were diagnostic of diabetes. Table 2 shows the crude age- and sex-specific prevalence [n (%)] of plasma glucose diagnostic categories in Ghanaian subjects. The oldest age group (64+ years) had the highest diabetes prevalence (13.6%). Age standardization to the Ghanaian population yielded a diabetes prevalence of 6.1%; the corresponding prevalence of IFG and IGT, were 6.1 and 10.5%, respectively. The prevalence rate of diabetes, IFG and IGT, adjusted to the new world standard population [23], were 6.4, 6.0, 10.7%, respectively. The corresponding adjusted diabetes prevalence was higher in males than in females (7.7 vs. 5.5%; P B 0.05). Mean characteristics (9 SD) of subjects in the various plasma glucose categories by sex are shown in Table 3. In Table 4, demographic characteristics of respondents are contrasted with those of 558 non-respondents.
4. Discussion The health care policy in Ghana places little emphasis on diabetes control and prevention, due to the belief that the disease is rare among
Table 1 Phenotypic characteristics of the Ghanaian subjects studied Variable
Male
Female
P
All
n Age (years) BMI (kg/m2) FPG (mmol/l) 2-hPG (mmol/l) Heart rate (/min) SBP (mmHg) DBP (mmHg)
1860 44.9 9 14.7 22.6 93.9 5.5 91.1 7.092.0 75910 1299 22 75913
2873 44.0 914.6 25.6 9 5.8 5.4 9 1.3 7.0 92.2 79 9 11 129 9 26 75 9 14
B0.05 B0.001 B0.003 \0.05 B0.001 \0.05 \0.05
4733 44.3 914.7 24.4 95.3 5.5 91.2 7.0 92.1 78 911 129 9 25 75 914
Mean9SD; BMI, body mass index; FPG, fasting plasma glucose; 2-hPG, 2-h plasma glucose; DBP, diastolic blood pressure; SBP, systolic blood pressure.
n (%).
n 25–34 35–44 45–54 55–64 64+
Age group (years)
2153 768(85.3) 610(79.8) 398(70.9) 211(66.1) 166(50.2)
1309 460(82.9) 326(73.4) 245(62.7) 157(63.4) 121(54.5)
3462 1228(84.4) 936(77.5) 643(67.5) 368(65.1) 287(51.9)
143 38(6.8) 35(7.9) 40(10.2) 21(8.5) 9(4.1)
M
F
M
All
IFG
Normal fasting and glucose tolerance
146 31(3.4) 45(5.9) 32(5.7) 17(5.3) 21(6.3)
F 289 69(4.7) 80(6.6) 72(7.6) 38(6.7) 30(5.4)
All
Table 2 Crude age- and sex-specific prevalence of plasma glucose diagnostic categories in Ghanaian subjects
178 31(5.6) 33(7.4) 44(11.3) 25(10.2) 45(20.3)
M
IGT
324 66(7.3) 58(7.6) 73(13.0) 41(12.9) 86(26.0)
F
502 97(6.7) 91(7.5) 117(12.3) 66(11.7) 131(23.7)
All
83 15(2.7) 22(5.0) 20(5.1) 11(4.5) 15(6.8)
M
97 16(1.8) 21(2.7) 19(3.4) 26(8.2) 15(4.5)
F
IFG and IGT
180 31(2.1) 43(3.6) 39(4.1) 37(6.5) 30(5.4)
All
145 11(2.0) 28(6.3) 42(10.7) 32(13.0) 32(14.4)
M
Diabetes
155 19(2.1) 30(3.9) 39(7.0) 24(7.5) 43(13.0)
F
300 30(2.1) 58(4.8) 81(8.5) 56(9.9) 75(13.6)
All
A.G.B. Amoah et al. / Diabetes Research and Clinical Practice 56 (2002) 197–205 201
73913
73913b
749 12
779 13
1329 22
7.090.4
6.390.2
80916b
137928b
6.9 90.4b
78915
134925
7.090.4
6.390.2
b
139 929b 78 914b
77 914
8.7 90.8b
5.390.5b
916.5 26.8 9 6.1a
51.1
F
134925
8.7 90.8
5.490.4
22.8 94.4
51.4 9 16.7
M
IGT
77914
1379 28
8.790.8
5.490.5
25.396.4
51.2916.6
All
Mean9 SD; FPG, fasting plasma glucose; 2-hPG, 2-h plasma glucose; SBP, systolic blood pressure; DPB, diastolic blood pressure. a t-test: male vs female, PB0.05. b t-test: male versus female, P\0.05; ANOVA comparing glucose tolerant categories. c PB0.05.
125923
1259 24b
126 920
SBP (mmHg) DBP (mmHg)
6.390.7
6.3 9 0.7a
6.29 0.7
2-hPG (mmol/l)
5.290.5
5.1 9 0.5a
6.3 90.2b
24.595.1
24.095.0
9 13.6 25.1 9 5.5a 23.093.8
9 14.5 25.9 95.7a b
45.69 13.9
42.2913.8
41.8 a
46.3
42.8914
44.8 913.2
All
F
M
All
M
F
IFG
Normal fasting and glucose tolerance
BMI 22.2 93.5 (kg/m2) FPG 5.29 0.5 (mmol/l)
Age (years)
Variable
Table 3 Characteristics of subjects in the plasma glucose categories by sex
799 14
138923
9.09 0.9
6.49 0.2
b
809 17b
143 9 31b
8.8 9 0.8b
6.4 9 0.3b
9 15.1 28.1 9 7.0a
50.6
49.2 9 15.4 23.5 9 4.4
F
M
IFG and IGT
79915
1419 28
8.99 0.9
6.49 0.3
26.096.4
49.9915.2
All
83914
1449 25
11.8 9 4.0
7.7 9 2.7
25.1 95.1
53.1913.0
M
Diabetes
b
81914b
147933b
13.09 5.7a
8.393.9b
9 15.3 28.096.9a
52.7
F
82914c
1469 30c
12.495.0c
8.09 3.4c
26.696.3c
52.9914.2c
All
202 A.G.B. Amoah et al. / Diabetes Research and Clinical Practice 56 (2002) 197–205
A.G.B. Amoah et al. / Diabetes Research and Clinical Practice 56 (2002) 197–205 Table 4 Comparison of survey participants with a random sample of non-respondents with respect to selected demographic variables Variable
Respondents
Non-respondents
n Age (years) Sex (F:M)
4733 44.3 914.7 1.5:1.0
558 40.2 9 20.7a 1.2:1.0
Age groups (%) (years)b 25–34 35–44 45–54 55–64 64+
30.8 25.5 20.1 12.0 11.6
46 25.5 13.9 5.2 9.4
1.9
0.9
Prior history of diabetes (%) a b
Mean 9SD; PB0.001. Pearson 2, PB0.001.
Ghanaians [1,24]. We provide for the first time, diabetes prevalence data in adult Ghanaians, using current recommended diagnostic criteria [16,17]. Adjusting the crude prevalence rate to the adult Ghanaian population or to the ‘new’ world standard population [23] did not result in great differences in the rates of diabetes. Adjustment to the new world standard population resulted in a diabetes prevalence of 6.4%, confirming that diabetes is not rare in adult Ghanaians. The relatively high rate of diabetes has important public health implications for health planners. Ghana is a low-income country [19] with a heavy burden of infectious diseases. That the level of non-communicable diseases like diabetes is also relatively high is likely to increase the financial burden on the economy. There is an urgent need therefore for a health policy shift towards control and prevention of diabetes in Ghanaians considering the expected rise in the rate of diabetes [25] that is likely to accompany increasing urbanization and acculturation. We report a higher prevalence of diabetes than some recent studies from Africa [11– 14]. It is of interest that, using the new ADA criteria to review studies in Cameroon, South Africa and Tanzania, diabetes prevalence between 0.7 and 10.6% have been reported [18]. People with African an-
203
cestry in the Caribbean and more so in the UK and the USA have relatively higher rates of diabetes compared to native West Africans [12,13]. Cooper et al. [13] demonstrated a rising gradient of diabetes in people of African ancestry from Nigeria through the Caribbean to the UK and U.S. Ghanaians and other West Africans share ethno-genetic links with people of African Ancestry in the Caribbean and USA [26]. Thus, the potential for the relatively high rates of Type 2 diabetes occurring in native West Africans exist, as the region undergoes epidemiologic transition with increasing urbanization and acculturation. Our figure for undiagnosed diabetes reported here (69.9%) is higher than that reported for developed countries [27–29] and for some developing countries [30]. The relatively high rates of previously undiagnosed diabetes in our subjects, reflects lack of diabetes awareness in Ghana. Often Ghanaian patients with symptoms of hyperglycaemia initially consult traditional healers, and therefore present late with diabetes complications to health care professionals. The high level of undiagnosed cases of diabetes should therefore help health workers to focus on public education to heighten diabetes awareness and on the early detection and management of the disease. Integration of diabetes care into primary care may thus prove cost effective. The prevalence of impaired fasting glycaemia in our subjects (6.1%) was similar to that reported recently in Jamaicans [30]. In some communities in sub-Saharan Africa, higher rates of IFG have been reported [18]. Also nearly 11% of our subjects had impaired glucose tolerance. Generally, worsening glycaemic status was associated with increasing age, body mass index, systolic blood pressure and diastolic blood pressure. Predictors for diabetes in Ghanaians and the pathophysiological significance of the relatively high prevalence level of IFG and IGT in Ghanaians, however, remain to be determined in future studies. A drawback of our study was that it was not based on a representative national sample. Also we provide no data on Type 1 diabetes. No C-peptide or GAD studies are presented. None of our diabetic subjects however, had Type 1 dia-
204
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betes. The World Health Organization recommends dietary preparation before the oral glucose tolerance test. No special dietary preparation could be enforced in our study. Generally, Ghanaians consume a relatively high carbohydrate diets with carbohydrate content far in excess of 250 g daily. Subjects were also encouraged to prepare correctly for the survey and to adhere to prior instructions regarding fasting and the oral glucose tolerance test. Also compared to respondents, our non-respondents were relatively younger, and they were less likely to have prior diabetes. Thus, a slight over-estimation of the prevalence of diabetes in our respondents cannot be discounted. Our study, carried out in a cluster sample of adults in purposively selected communities in the Greater Accra area of Ghana, nevertheless provides useful data on diabetes prevalence in Ghanaians. In conclusion our study has revealed that diabetes is not rare in Ghanaians. For the first time, objective data on the prevalence of diabetes and IFG and IGT, using recommended diagnostic criteria for diabetes are available. Such information may assist health planners in Ghana to formulate prevention and control programmes for diabetes.
Acknowledgements We wish to thank Twumasi-Ankrah, Tweneboa-Kodua (Ghana Statistical Service, Accra), Thomas Ndanu, Nana Esi Nkumah Amoah (Field Coordinators, Ghana Non-communicable Diseases Survey, NCDS 98), Mercy Abbey (Health Research Unit, Ministry of Health, Accra) and our survey personnel for their assistance. We are also thankful to Charles Oppong and Henry Edu (Diabetes Research Laboratory, Department of Medicine, University of Ghana Medical School) for their assistance with laboratory analyses. We are also grateful to World Health Organization (Accra, Brazzaville and Geneva offices), Dr Hilary King, WHO, Geneva; Professor Jaako Tuomilehto, National Public Health Institute, Helsinki, Finland; Professor Charles Rotimi, Loyola University, Chicago, USA and
Professors Kwame Osei and Rev. Seth Ayettey for their helpful suggestions. The assistance of Mirjana Vekich, Loyola University, Chicago, USA is acknowledged. Our thanks also go to George Mensah, Noguchi Memorial Institute, University of Ghana, Legon. Financial assistance from Eli Lilly and Company Foundation, USA and the Ghana Ministry of Health is acknowledged. This work was supported by Eli Lilly and Company Foundation, USA, Ghana Ministry of Health, National Diabetes Management and Research Centre, Korle Bu, Accra.
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Diabetes in Ghana: a community based prevalence study in Greater Accra Albert G.B. Amoah a,b,*, Samuel K. Owusu a,b, Samuel Adjei c a
Department of Medicine and Therapeutics, Diabetes Research Laboratory, Uni6ersity of Ghana Medical School, P.O. Box 4236, Accra, Ghana b National Diabetes Management and Research Centre, Korle Bu Teaching Hospital, Accra, Ghana c Health Research Unit, Ministry of Health, Accra, Ghana Received 15 March 2001; received in revised form 24 November 2001; accepted 4 December 2001
Abstract Data on the prevalence of diabetes in Ghana is scanty and unreliable. In the present study we have ascertained the prevalence of diabetes, impaired fasting glycaemia (IFG) and impaired glucose tolerance (IGT) in a random cluster sample of Ghanaians aged 25 years and above from the Greater Accra area of Ghana. Diabetes, IFG and IGT were defined by criteria of the American Diabetes Association and World Health Organization. The mean age of the 4733 subjects involved in the study was 44.3 9 14.7 years, and participation rate was 75%. The crude prevalence of diabetes was 6.3%. Out of 300 subjects with diabetes, 209 (69.7%) had no prior history of the disease. Diabetes, IGT and combined IFG and IGT increased with age. The oldest age group (64 + years) had the highest diabetes prevalence (13.6%). The age-adjusted prevalence of diabetes, IFG and IGT, were 6.4, 6.0 and 10.7%, respectively. Diabetes was more common in males than females (7.7 vs. 5.5%) [PB 0.05]. Worsening glycaemic status tended to be associated with increase in age, body mass index, systolic and diastolic blood pressures. Ascertainment of predictors for diabetes in Ghanaians and the significance of the relatively high rates of and IFG and IGT however, remain to be determined. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Type 2 diabetes; Prevalence; Impaired fasting glycaemia; Impaired glucose tolerance; Ghana
1. Introduction The prevalence of diabetes in sub-Saharan Africa had been estimated between 0.0 and 1.9% [1 – 12]. Recent studies from urban Cameroon, Nigeria and Tanzania suggest that the disease may now be more common in sub-Saharan Africa than previously * Corresponding author. Tel./fax: +233-21-67-1047. E-mail address: [email protected] (A.G.B. Amoah).
thought [12 –14]. In Ghana, information on the prevalence of diabetes is scanty and outdated. In 1958, using urinalysis for diabetes screening, Dodu [1] found a diabetes prevalence of 0.4% among 4000 urban outpatient population in Accra. In a community sample of 5000 subjects from a provincial capital in Ghana, Dodu and de Heer [15] reported a diabetes prevalence of 0.2%. Based on these figures, the impression was created among policy makers that diabetes is rare in Ghanaians.
0168-8227/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 1 6 8 - 8 2 2 7 ( 0 1 ) 0 0 3 7 4 - 6
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The diagnostic criteria for diabetes have recently been revised by an Expert Committee of the American Diabetes Association (ADA) [16] and by a World Health Organization (WHO) consultation [17]. The threshold of fasting plasma glucose for diabetes has been lowered to 7.0 mmol/l and an additional category, impaired fasting glycaemia (IFG) has been proposed as a new group with increased risk of developing diabetes [16,17]. Additionally, the WHO retained the 2-h glucose criteria for diagnosis of diabetes [17]. The new diagnostic criteria have recently been employed to review previously published studies in Africans [18]. Ghana is a tropical country in West Africa with a surface area of 238,533 km2. The population in 2000 was 19.7 million with a gross domestic product (GDP) of US$ 7.4 bn and per capita GDP of US$ 412. The Accra metropolitan area is the largest urban population (1.6 million) [19]. In 1998, a non-communicable diseases survey (NCDS 98) was initiated to determine the prevalence of diabetes, hypertension, obesity, ischaemic heart disease and cardiovascular risk factors in selected communities in this area. In this communication, we report the prevalence of diabetes, IFG and IGT in the Greater Accra area, using the new diagnostic criteria [16,17].
2. Patients and methods
2.1. Target population and sampling For ease of survey, two urban communities in the Accra metropolis (Labadi/Cantoments and Teshie), together with one area of rural Accra (Danfa/Abokobi, 20 villages) were selected as representative. A stratified two-stage cluster sampling technique was used. A sample size of 752 was determined based on an estimate of diabetes prevalence of 2%, an absolute precision of 1% and a confidence interval of 95%, in accordance with the Statcalc function of Epi Info, Version 6 (Center for Diseases Control, Atlanta, Georgia, USA, and World Health Organization, Geneva, Switzerland). This sample size was multiplied by the maximum design effect
for clustering of two to give a sample of 1504. To allow for a non-response rate of 20% and nonparticipation rate of 10%, a final sample size of 2100 per community was employed. The Ghana Statistical Service randomly selected 14 census enumeration zones from each of the two urban communities. From each zone, adults aged ] 25 years were listed, and 150 eligible subjects were subsequently selected by systematic random sampling per enumeration area to participate in the study. In the rural area, all eligible adults were listed and randomized. From each of the three survey communities, 2100 subjects were recruited into the study.
2.2. Sur6ey personal A 19-member team made up of a graduate field coordinator, three senior public health nurses, one state registered nurse, three university graduates and 11 pre-university students were trained and supervised to perform household listing by the Ghana Statistical Service. Five laboratory technicians, one phlebotomist, four additional senior public health nurses, one community health nurse and two pre-university students were subsequently recruited to join 17 members of the original census team for the actual survey. To standardize survey measurements and procedures, the survey team was trained using specially prepared survey manuals that conformed to recommended noncommunicable disease survey protocols [20]. Three of the senior public health nurses were trained and certified to measure blood pressure accurately, using a double headed stethoscope and resource material from Shared Care (Accurate blood pressure measurement, a video course. Torrance, CA, USA).
2.3. Sur6ey methods Fasting blood samples was taken from subjects before 10:00 h. Subjects then drank the equivalent of 75 g of anhydrous glucose in 300 ml of water and a second blood sample was taken 2 h after the glucose drink. During the OGTT, subjects did not engage in strenuous activity or smoke. Fluoridated blood samples were kept on ice and cen-
A.G.B. Amoah et al. / Diabetes Research and Clinical Practice 56 (2002) 197–205
trifuged within 15 min. The resultant plasma was frozen on dry ice in the field and transported frozen to be stored at − 80° C until analyzed. Plasma glucose was determined with glucose oxidase kits (Randox Laboratories Ltd., Crumlin, UK) on an automatic chemistry analyzer (Erba Smartlab, Mumbai, India) at the Diabetes Research Laboratory of the University of Ghana Medical School, Accra. Anthropometric measurements were performed on subjects in light clothing and without shoes. Weight was measured with a heavy duty Seca 770 floor digital scale (Hamburg, Germany) to the nearest 0.1 kg. Height was measured with a height measure to the nearest millimetre. Body mass index (BMI) was calculated from the weight and height measurements. After at least 10 min rest, blood pressure was measured to the nearest 2 mmHg, in the right arm of seated subjects on two occasions at an interval of 1 min with a mercury sphygmomanometer and a cuff of appropriate size. Demographic data and information on diabetes status/treatment were subsequently determined with the aid of a structured questionnaire. After the survey, demographic data were also obtained from 558 randomly selected non-respondents from the survey communities.
2.4. Sur6ey facilitation and quality assurance Before the main survey, a field trial was conducted. This involved 60 subjects from outside the three survey communities. The field trial enabled fine-tuning of survey procedures and measurements. Before and during the survey period, local resource personnel went round the community in mobile vans equipped with public address systems, each evening (18:00 h) and morning (05:00 h), to remind survey subjects to prepare correctly for the survey and to report at the survey site on time. The local resource personnel also visited scheduled participants in their homes each evening to remind them to fast correctly and report to the survey site on time. In Teshie and to a greater extent in the rural Accra, survey subjects were bussed to the survey site each morning
199
to ensure they did not have to walk long distances and to help them arrive on time. To ensure the accuracy of BP readings, the three nurses certified to measure blood pressure were re-certified every 3 weeks during the 12week survey period, using the video. The weighing scale was checked against two reference scales each morning before commencement of weighing. Finally, data collection instruments were checked for accuracy and completeness of entries before subjects were discharged home from the survey site. Plasma glucose was determined in duplicate and normal and elevated commercial control sera were run with a batch of samples from 20 subjects. The inter-assay coefficient of variation for normal and elevated plasma glucose controls was 1.4 and 2.4%, respectively, the corresponding intra-assay coefficient of variation was 1.8 and 1.4%, respectively.
2.5. Data analysis Data from the three communities were pooled together for the present report. Impaired fasting and oral glucose tolerance was defined in accordance with the new American Diabetes Association and World Health Organization criteria [16,17]. Diabetes was defined by a venous fasting plasma glucose of ] 7.0 mmol/l and/or 2-h venous plasma glucose of ]11.1 mmol/l [16,17] or treatment for diabetes (diet, oral glucose-lowering drug and/or insulin). Impaired glucose tolerance (IGT) [2-h plasma glucose 7.8–11.0 mmol/l] was ascertained in subjects without prior diabetes, whose fasting plasma glucose was B 7.0 mmol/l. Impaired fasting glycaemia (IFG) [fasting plasma glucose ]6.1 and B 7.0 mmol/l] was determined in subjects without prior diabetes, whose 2-h plasma glucose was less than 7.8 mmol/l. The statistical package SPSS 10.0 for Windows (SPSS Inc., Chicago, IL, USA) was used for analyses. Data are expressed as mean9 SD. Student’s unpaired, two-sided t-test was used to compare means between two groups and ANOVA for more than two groups. Chi-square was used in the comparison of proportions.
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Prevalence estimates were age-standardized to the Ghanaian population by the direct method [21] using a population estimate of 18.3 million and 5-year age groups from 25 years and above [22]. In addition, the prevalence estimate was age-adjusted to the ‘new’ world standard population [23].
2.6. Ethics The study was approved by the Ethical and Protocol Review Committee of the University of Ghana Medical School and complied with the Helsinki Declaration of 1975 (revised in 1983 and 1989) on human experimentation. Informed consent was obtained from all participants.
3. Results Out of a total of 6300 subjects selected, 4733 subjects participated in the study, giving a response rate of 75%. The response rates in the first, second and third communities were 70, 77 and 77%, respectively. Table 1 shows the mean9 SD of selected variables for males and females and for the total study population. The mean age of subjects was 44.39 14.7 years. Males were older and had lower BMI than females. The crude prevalence of diabetes in all subjects was 6.3%. The corresponding prevalence of IFG (n =289) and IGT (n= 502) separately were 6.1 and 10.6%, respectively. An additional 180 (3.8%) subjects had combined IFG and IGT. The crude diabetes
prevalence in the first, second and third communities were 7.3, 5.9, 5.9% (PB 0.05), respectively. Out of 300 subjects with diabetes, 209 (69.7%) had no prior history of diabetes. Diabetes was diagnosed by fasting plasma glucose alone in 65 subjects (21.7%). In 62 subjects (20.7%), diabetes was diagnosed by OGTT alone. In another 82 subjects (27.3%), both the fasting plasma glucose and OGTT were diagnostic of diabetes. Table 2 shows the crude age- and sex-specific prevalence [n (%)] of plasma glucose diagnostic categories in Ghanaian subjects. The oldest age group (64+ years) had the highest diabetes prevalence (13.6%). Age standardization to the Ghanaian population yielded a diabetes prevalence of 6.1%; the corresponding prevalence of IFG and IGT, were 6.1 and 10.5%, respectively. The prevalence rate of diabetes, IFG and IGT, adjusted to the new world standard population [23], were 6.4, 6.0, 10.7%, respectively. The corresponding adjusted diabetes prevalence was higher in males than in females (7.7 vs. 5.5%; P B 0.05). Mean characteristics (9 SD) of subjects in the various plasma glucose categories by sex are shown in Table 3. In Table 4, demographic characteristics of respondents are contrasted with those of 558 non-respondents.
4. Discussion The health care policy in Ghana places little emphasis on diabetes control and prevention, due to the belief that the disease is rare among
Table 1 Phenotypic characteristics of the Ghanaian subjects studied Variable
Male
Female
P
All
n Age (years) BMI (kg/m2) FPG (mmol/l) 2-hPG (mmol/l) Heart rate (/min) SBP (mmHg) DBP (mmHg)
1860 44.9 9 14.7 22.6 93.9 5.5 91.1 7.092.0 75910 1299 22 75913
2873 44.0 914.6 25.6 9 5.8 5.4 9 1.3 7.0 92.2 79 9 11 129 9 26 75 9 14
B0.05 B0.001 B0.003 \0.05 B0.001 \0.05 \0.05
4733 44.3 914.7 24.4 95.3 5.5 91.2 7.0 92.1 78 911 129 9 25 75 914
Mean9SD; BMI, body mass index; FPG, fasting plasma glucose; 2-hPG, 2-h plasma glucose; DBP, diastolic blood pressure; SBP, systolic blood pressure.
n (%).
n 25–34 35–44 45–54 55–64 64+
Age group (years)
2153 768(85.3) 610(79.8) 398(70.9) 211(66.1) 166(50.2)
1309 460(82.9) 326(73.4) 245(62.7) 157(63.4) 121(54.5)
3462 1228(84.4) 936(77.5) 643(67.5) 368(65.1) 287(51.9)
143 38(6.8) 35(7.9) 40(10.2) 21(8.5) 9(4.1)
M
F
M
All
IFG
Normal fasting and glucose tolerance
146 31(3.4) 45(5.9) 32(5.7) 17(5.3) 21(6.3)
F 289 69(4.7) 80(6.6) 72(7.6) 38(6.7) 30(5.4)
All
Table 2 Crude age- and sex-specific prevalence of plasma glucose diagnostic categories in Ghanaian subjects
178 31(5.6) 33(7.4) 44(11.3) 25(10.2) 45(20.3)
M
IGT
324 66(7.3) 58(7.6) 73(13.0) 41(12.9) 86(26.0)
F
502 97(6.7) 91(7.5) 117(12.3) 66(11.7) 131(23.7)
All
83 15(2.7) 22(5.0) 20(5.1) 11(4.5) 15(6.8)
M
97 16(1.8) 21(2.7) 19(3.4) 26(8.2) 15(4.5)
F
IFG and IGT
180 31(2.1) 43(3.6) 39(4.1) 37(6.5) 30(5.4)
All
145 11(2.0) 28(6.3) 42(10.7) 32(13.0) 32(14.4)
M
Diabetes
155 19(2.1) 30(3.9) 39(7.0) 24(7.5) 43(13.0)
F
300 30(2.1) 58(4.8) 81(8.5) 56(9.9) 75(13.6)
All
A.G.B. Amoah et al. / Diabetes Research and Clinical Practice 56 (2002) 197–205 201
73913
73913b
749 12
779 13
1329 22
7.090.4
6.390.2
80916b
137928b
6.9 90.4b
78915
134925
7.090.4
6.390.2
b
139 929b 78 914b
77 914
8.7 90.8b
5.390.5b
916.5 26.8 9 6.1a
51.1
F
134925
8.7 90.8
5.490.4
22.8 94.4
51.4 9 16.7
M
IGT
77914
1379 28
8.790.8
5.490.5
25.396.4
51.2916.6
All
Mean9 SD; FPG, fasting plasma glucose; 2-hPG, 2-h plasma glucose; SBP, systolic blood pressure; DPB, diastolic blood pressure. a t-test: male vs female, PB0.05. b t-test: male versus female, P\0.05; ANOVA comparing glucose tolerant categories. c PB0.05.
125923
1259 24b
126 920
SBP (mmHg) DBP (mmHg)
6.390.7
6.3 9 0.7a
6.29 0.7
2-hPG (mmol/l)
5.290.5
5.1 9 0.5a
6.3 90.2b
24.595.1
24.095.0
9 13.6 25.1 9 5.5a 23.093.8
9 14.5 25.9 95.7a b
45.69 13.9
42.2913.8
41.8 a
46.3
42.8914
44.8 913.2
All
F
M
All
M
F
IFG
Normal fasting and glucose tolerance
BMI 22.2 93.5 (kg/m2) FPG 5.29 0.5 (mmol/l)
Age (years)
Variable
Table 3 Characteristics of subjects in the plasma glucose categories by sex
799 14
138923
9.09 0.9
6.49 0.2
b
809 17b
143 9 31b
8.8 9 0.8b
6.4 9 0.3b
9 15.1 28.1 9 7.0a
50.6
49.2 9 15.4 23.5 9 4.4
F
M
IFG and IGT
79915
1419 28
8.99 0.9
6.49 0.3
26.096.4
49.9915.2
All
83914
1449 25
11.8 9 4.0
7.7 9 2.7
25.1 95.1
53.1913.0
M
Diabetes
b
81914b
147933b
13.09 5.7a
8.393.9b
9 15.3 28.096.9a
52.7
F
82914c
1469 30c
12.495.0c
8.09 3.4c
26.696.3c
52.9914.2c
All
202 A.G.B. Amoah et al. / Diabetes Research and Clinical Practice 56 (2002) 197–205
A.G.B. Amoah et al. / Diabetes Research and Clinical Practice 56 (2002) 197–205 Table 4 Comparison of survey participants with a random sample of non-respondents with respect to selected demographic variables Variable
Respondents
Non-respondents
n Age (years) Sex (F:M)
4733 44.3 914.7 1.5:1.0
558 40.2 9 20.7a 1.2:1.0
Age groups (%) (years)b 25–34 35–44 45–54 55–64 64+
30.8 25.5 20.1 12.0 11.6
46 25.5 13.9 5.2 9.4
1.9
0.9
Prior history of diabetes (%) a b
Mean 9SD; PB0.001. Pearson 2, PB0.001.
Ghanaians [1,24]. We provide for the first time, diabetes prevalence data in adult Ghanaians, using current recommended diagnostic criteria [16,17]. Adjusting the crude prevalence rate to the adult Ghanaian population or to the ‘new’ world standard population [23] did not result in great differences in the rates of diabetes. Adjustment to the new world standard population resulted in a diabetes prevalence of 6.4%, confirming that diabetes is not rare in adult Ghanaians. The relatively high rate of diabetes has important public health implications for health planners. Ghana is a low-income country [19] with a heavy burden of infectious diseases. That the level of non-communicable diseases like diabetes is also relatively high is likely to increase the financial burden on the economy. There is an urgent need therefore for a health policy shift towards control and prevention of diabetes in Ghanaians considering the expected rise in the rate of diabetes [25] that is likely to accompany increasing urbanization and acculturation. We report a higher prevalence of diabetes than some recent studies from Africa [11– 14]. It is of interest that, using the new ADA criteria to review studies in Cameroon, South Africa and Tanzania, diabetes prevalence between 0.7 and 10.6% have been reported [18]. People with African an-
203
cestry in the Caribbean and more so in the UK and the USA have relatively higher rates of diabetes compared to native West Africans [12,13]. Cooper et al. [13] demonstrated a rising gradient of diabetes in people of African ancestry from Nigeria through the Caribbean to the UK and U.S. Ghanaians and other West Africans share ethno-genetic links with people of African Ancestry in the Caribbean and USA [26]. Thus, the potential for the relatively high rates of Type 2 diabetes occurring in native West Africans exist, as the region undergoes epidemiologic transition with increasing urbanization and acculturation. Our figure for undiagnosed diabetes reported here (69.9%) is higher than that reported for developed countries [27–29] and for some developing countries [30]. The relatively high rates of previously undiagnosed diabetes in our subjects, reflects lack of diabetes awareness in Ghana. Often Ghanaian patients with symptoms of hyperglycaemia initially consult traditional healers, and therefore present late with diabetes complications to health care professionals. The high level of undiagnosed cases of diabetes should therefore help health workers to focus on public education to heighten diabetes awareness and on the early detection and management of the disease. Integration of diabetes care into primary care may thus prove cost effective. The prevalence of impaired fasting glycaemia in our subjects (6.1%) was similar to that reported recently in Jamaicans [30]. In some communities in sub-Saharan Africa, higher rates of IFG have been reported [18]. Also nearly 11% of our subjects had impaired glucose tolerance. Generally, worsening glycaemic status was associated with increasing age, body mass index, systolic blood pressure and diastolic blood pressure. Predictors for diabetes in Ghanaians and the pathophysiological significance of the relatively high prevalence level of IFG and IGT in Ghanaians, however, remain to be determined in future studies. A drawback of our study was that it was not based on a representative national sample. Also we provide no data on Type 1 diabetes. No C-peptide or GAD studies are presented. None of our diabetic subjects however, had Type 1 dia-
204
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betes. The World Health Organization recommends dietary preparation before the oral glucose tolerance test. No special dietary preparation could be enforced in our study. Generally, Ghanaians consume a relatively high carbohydrate diets with carbohydrate content far in excess of 250 g daily. Subjects were also encouraged to prepare correctly for the survey and to adhere to prior instructions regarding fasting and the oral glucose tolerance test. Also compared to respondents, our non-respondents were relatively younger, and they were less likely to have prior diabetes. Thus, a slight over-estimation of the prevalence of diabetes in our respondents cannot be discounted. Our study, carried out in a cluster sample of adults in purposively selected communities in the Greater Accra area of Ghana, nevertheless provides useful data on diabetes prevalence in Ghanaians. In conclusion our study has revealed that diabetes is not rare in Ghanaians. For the first time, objective data on the prevalence of diabetes and IFG and IGT, using recommended diagnostic criteria for diabetes are available. Such information may assist health planners in Ghana to formulate prevention and control programmes for diabetes.
Acknowledgements We wish to thank Twumasi-Ankrah, Tweneboa-Kodua (Ghana Statistical Service, Accra), Thomas Ndanu, Nana Esi Nkumah Amoah (Field Coordinators, Ghana Non-communicable Diseases Survey, NCDS 98), Mercy Abbey (Health Research Unit, Ministry of Health, Accra) and our survey personnel for their assistance. We are also thankful to Charles Oppong and Henry Edu (Diabetes Research Laboratory, Department of Medicine, University of Ghana Medical School) for their assistance with laboratory analyses. We are also grateful to World Health Organization (Accra, Brazzaville and Geneva offices), Dr Hilary King, WHO, Geneva; Professor Jaako Tuomilehto, National Public Health Institute, Helsinki, Finland; Professor Charles Rotimi, Loyola University, Chicago, USA and
Professors Kwame Osei and Rev. Seth Ayettey for their helpful suggestions. The assistance of Mirjana Vekich, Loyola University, Chicago, USA is acknowledged. Our thanks also go to George Mensah, Noguchi Memorial Institute, University of Ghana, Legon. Financial assistance from Eli Lilly and Company Foundation, USA and the Ghana Ministry of Health is acknowledged. This work was supported by Eli Lilly and Company Foundation, USA, Ghana Ministry of Health, National Diabetes Management and Research Centre, Korle Bu, Accra.
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