- Email: [email protected]
Obesity and other risk factors for cardiovascular diseases among Africans: results from CARDIAC study in Tanzania
International Congress Series 1262 (2004) 372 – 375
www.ics-elsevier.com
Obesity and other risk factors for cardiovascular diseases among Africans: results from CARDIAC study in Tanzania Marina Njelekela a,*, Katsumi Ikeda b, Jacob Mtabaji a, Yukio Yamoric On behalf of the WHO-cardiovascular diseases and alimentary comparison (CARDIAC) study group a
Department of Physiology, School of Medicine, Muhimbili University College of Health Sciences, P.O. Box 65001, Dar es salaam, Tanzania b Department of Human and Environmental Science, Mukogawa Women’s University, Koshien, Hyogo, Japan c WHO Center for Primary Prevention of CVD, Kyoto, Japan
Abstract. Objective: To investigate the prevalence of obesity and central adiposity and to assess if any significant relationship exists between obesity and other risk factors for cardiovascular diseases (CVD) in an African population. Methods: A cross-sectional, epidemiological study was conducted in three distinct areas: urban, rural and a pastoralist population in Tanzania. Results: The overall prevalence of obesity (body mass index (BMI) z 30 kg/m2) was 14.2% and that of adiposity was 16.9%. Of the obese participants, 40.5% had reached higher education levels and 59.1% lived in the urban area. Significant hypertension (48.1%), hypercholesterolemia (32.4%), hypertriglyceridemia (20.3%), elevated LDL-C (33.8%), and hyperglycemia (4.6%) were seen among obese participants. Elevated plasma leptin concentration and low REE were observed among obese participants. Conclusion: Obesity, associated with significant biochemical derangement, is now a health problem in Tanzania. Effective strategies for primary prevention of obesity need to be introduced, especially in urban areas in Tanzania. D 2003 Elsevier B.V. All rights reserved. Keywords: Obesity; CVD risk factors; Urban; Education; Occupation; Africans
1. Introduction Many developing countries, including Tanzania, are still contending with infectious diseases although the prevalence of a number of non-communicable diseases, such as diabetes and hypertension, is increasing rapidly, particularly in urban areas [1]. Obesity is one of the modifiable major risk factors for cardiovascular diseases (CVD) and one of the * Corresponding author. Tel.: +255-22-2150302; fax: +255-22-2150465. E-mail address: [email protected] (M. Njelekela). 0531-5131/ D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2003.11.047
M. Njelekela et al. / International Congress Series 1262 (2004) 372–375
373
contributing factors in the development of diabetes and hypertension [2]. In some African countries, the prevalence of obesity has been found to be higher in urban areas as compared with rural areas [3]. Factors contributing towards obesity in African countries have also been previously reported [4]. With a higher body mass index (BMI), other CVD risk factors, such as hypertension, hypercholesterolemia, and hyperglycemia, tend to be elevated as well. Thus, this study reports on the prevalence of obesity and central adiposity and assesses if any significant relationship exists between obesity and other risk factors for CVD in Tanzania. 2. Materials and methods Data for this study were collected as part of the CARDIAC-MONALISA (MONeo ALImentation SAnae) Study, which was conducted in Tanzania in 1998. The study aimed at monitoring past trends in the populations previously included in the original CARDIAC study. The methodology has been described in detail in one of our previous publications [5]. In summary, the survey involved approximately 100 men and 100 women aged 46 –58 years from the three areas of Dar es Salaam, Handeni and Monduli, respectively. Anthropometric measurements and BP were measured. REE was estimated using Hosoya’s portable indirect calorimeter (HPIC, METAVINE, VINE Limited, Osaka, Japan). In this analysis, education and occupation were taken as measures of socio-economic status (SES) [6]. Samples of blood and urine were shipped to the central WHO CARDIAC Study laboratory in Kyoto, Japan, for analysis. 3. Statistical analysis All analyses were done using Stat view statistical software. The difference between the means across groups was tested by analysis of variance. Proportions were compared by contingency table analysis with a chi (v2) square test. Statistical significance was defined as p < 0.05. Separate analyses were conducted for men and women. 4. Results The analysis included 545 participants from the three distinct areas. The response rate was 90.8%. The overall prevalence of obesity (BMI z 30 kg/m2) was 14.2% and that of central adiposity (WC >102 cm) was 16.9% among men and 49.6% among women (WC > 88 cm). Participants from the urban area showed a significantly higher mean weight, WC, BMI, and blood pressure level, a higher prevalence of obesity and central adiposity compared with those in the rural and pastoralist populations. Resting energy expenditure was highest among the pastoralists and participants from rural areas (results not shown). Fig. 1 shows the prevalence of CVD risk factors among lean, obese and morbidly obese participants for both men and women. The overall prevalence of hypertension was 48.1%, hypercholesterolemia 32.4%, hypertriglyceridemia 20.3%, elevated LDL-C 33.8%, and hyperglycemia 4.6%, respectively. Of the obese participants, 40.5% had formal education and 59.1% lived in the urban area. Participants who received formal education for 9 years or more showed a significantly higher BMI (men, p < 0.001, women p < 0.0001) and a higher prevalence of elevated HBA1c percent ( z 7%) (women 40.0%, p < 0.05). Consumption of
374
M. Njelekela et al. / International Congress Series 1262 (2004) 372–375
Fig. 1. Prevalence of risk factors for CVD among lean (L), obese (O) and morbidly obese (MO) men and women.
a high calorie diet, such as coconut milk and meat for more than 3 days in a week, was higher in the educated group: meat (men 52.7%, p < 0.001; women 30.4%, p < 0.0001) and coconut milk (men 51.9%, p < 0.001; women 32.3%, p < 0.0001), respectively. 5. Discussion The elevated BMI and waist circumference in urban dwellers and among skilled workers indicates that as people become more affluent obesity levels tend to increase [7]. The change in diet structure and acquisition of professional and leisure occupation strongly relate to urbanization [8], which results in a change in CVD risk factor pattern in the urban areas compared with rural areas. In most developing countries, obesity is not yet recognized as a major health problem and resources set for non-communicable disease prevention and treatment are few [1]. The findings of this study attest to an association between obesity with the expected lipid derangements that would constitute part of the predisposition to cardiovascular disease and the metabolic syndrome in urban areas in Africa. Both WC and BMI elevations are commonly associated with dyslipidemia [2,7]. Blood pressure levels and prevalence of hypertension increased with obesity. The
M. Njelekela et al. / International Congress Series 1262 (2004) 372–375
375
association between elevated BMI and hypertension has been reported in another study in Africa [9]. Obesity decreases insulin signal transduction of the insulin receptor leading to insulin resistance [10]. The findings of this study tend to reinforce the fact that diagnosing obesity and identifying an individual and populations at risk requires at most a measuring tape and a weighing scale. The derived BMI and WC allow the identification of ‘‘action points’’ for intervention. The addition of lipid measurements, blood pressure readings and a fasting blood sugar would enable clinical diagnosis of the metabolic syndrome, which should be a target for intensive therapeutic lifestyle changes. Acknowledgements We would like to express our sincere appreciation to our participants and to the Center for Primary Prevention of Cardiovascular Diseases Kyoto for funding this project. References [1] N. Unwin, et al., Noncommunicable diseases in sub-Saharan Africa: where do they feature in the health research agenda? Bull. World Health Organ., Suppl. 79 (2001) 907. [2] P. Poirier, et al., Obesity and cardiovascular disease, Curr. Atheroscler. Rep. 4 (2002) 448 – 453. [3] M.A. Van der Sande, et al., Blood pressure patterns and cardiovascular risk factors in rural and urban Gambian communities, J. Hum. Hypertens. 14 (2000) 489 – 496. [4] P. Bovet, et al., Distribution of blood pressure, body mass index and smoking habits in the urban population of Dar Es Salaam, Tanzania, and associations with economic status, Int. J. Epidemiol. 31 (2002) 240 – 247. [5] M. Njelekela, et al., Prevalence of obesity in middle aged men and women in Tanzania Africa: relationship with resting energy expenditure and dietary factors, J. Nutr. Sci. Vitaminol. 48 (2002) 352 – 358. [6] G.A. Kaplan, J.E. Keil, Socioeconomic factors and cardiovascular disease: a review of the literature, Circulation 88 (1993) 1973 – 1998. [7] R. Martorell, et al., Obesity in women from developing countries, Eur. J. Clin. Nutr. 54 (2000) 247 – 252. [8] B.M. Popkin, The nutrition transition in low-income countries: an emerging crisis, Nutr. Rev. 52 (1994) 285 – 298. [9] F.A. Ukoli, et al., Body fat distribution and other anthropometric blood pressure correlates in a Nigerian urban elderly population, Cent. Afr. J. Med. 41 (1995) 154 – 161. [10] G.L. Dohm, Mechanisms of muscle insulin resistance in obese individuals, Int. J. Sport Nutr. Exerc. Metab. 11 (2001) S64 – S70(Suppl.).
www.ics-elsevier.com
Obesity and other risk factors for cardiovascular diseases among Africans: results from CARDIAC study in Tanzania Marina Njelekela a,*, Katsumi Ikeda b, Jacob Mtabaji a, Yukio Yamoric On behalf of the WHO-cardiovascular diseases and alimentary comparison (CARDIAC) study group a
Department of Physiology, School of Medicine, Muhimbili University College of Health Sciences, P.O. Box 65001, Dar es salaam, Tanzania b Department of Human and Environmental Science, Mukogawa Women’s University, Koshien, Hyogo, Japan c WHO Center for Primary Prevention of CVD, Kyoto, Japan
Abstract. Objective: To investigate the prevalence of obesity and central adiposity and to assess if any significant relationship exists between obesity and other risk factors for cardiovascular diseases (CVD) in an African population. Methods: A cross-sectional, epidemiological study was conducted in three distinct areas: urban, rural and a pastoralist population in Tanzania. Results: The overall prevalence of obesity (body mass index (BMI) z 30 kg/m2) was 14.2% and that of adiposity was 16.9%. Of the obese participants, 40.5% had reached higher education levels and 59.1% lived in the urban area. Significant hypertension (48.1%), hypercholesterolemia (32.4%), hypertriglyceridemia (20.3%), elevated LDL-C (33.8%), and hyperglycemia (4.6%) were seen among obese participants. Elevated plasma leptin concentration and low REE were observed among obese participants. Conclusion: Obesity, associated with significant biochemical derangement, is now a health problem in Tanzania. Effective strategies for primary prevention of obesity need to be introduced, especially in urban areas in Tanzania. D 2003 Elsevier B.V. All rights reserved. Keywords: Obesity; CVD risk factors; Urban; Education; Occupation; Africans
1. Introduction Many developing countries, including Tanzania, are still contending with infectious diseases although the prevalence of a number of non-communicable diseases, such as diabetes and hypertension, is increasing rapidly, particularly in urban areas [1]. Obesity is one of the modifiable major risk factors for cardiovascular diseases (CVD) and one of the * Corresponding author. Tel.: +255-22-2150302; fax: +255-22-2150465. E-mail address: [email protected] (M. Njelekela). 0531-5131/ D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2003.11.047
M. Njelekela et al. / International Congress Series 1262 (2004) 372–375
373
contributing factors in the development of diabetes and hypertension [2]. In some African countries, the prevalence of obesity has been found to be higher in urban areas as compared with rural areas [3]. Factors contributing towards obesity in African countries have also been previously reported [4]. With a higher body mass index (BMI), other CVD risk factors, such as hypertension, hypercholesterolemia, and hyperglycemia, tend to be elevated as well. Thus, this study reports on the prevalence of obesity and central adiposity and assesses if any significant relationship exists between obesity and other risk factors for CVD in Tanzania. 2. Materials and methods Data for this study were collected as part of the CARDIAC-MONALISA (MONeo ALImentation SAnae) Study, which was conducted in Tanzania in 1998. The study aimed at monitoring past trends in the populations previously included in the original CARDIAC study. The methodology has been described in detail in one of our previous publications [5]. In summary, the survey involved approximately 100 men and 100 women aged 46 –58 years from the three areas of Dar es Salaam, Handeni and Monduli, respectively. Anthropometric measurements and BP were measured. REE was estimated using Hosoya’s portable indirect calorimeter (HPIC, METAVINE, VINE Limited, Osaka, Japan). In this analysis, education and occupation were taken as measures of socio-economic status (SES) [6]. Samples of blood and urine were shipped to the central WHO CARDIAC Study laboratory in Kyoto, Japan, for analysis. 3. Statistical analysis All analyses were done using Stat view statistical software. The difference between the means across groups was tested by analysis of variance. Proportions were compared by contingency table analysis with a chi (v2) square test. Statistical significance was defined as p < 0.05. Separate analyses were conducted for men and women. 4. Results The analysis included 545 participants from the three distinct areas. The response rate was 90.8%. The overall prevalence of obesity (BMI z 30 kg/m2) was 14.2% and that of central adiposity (WC >102 cm) was 16.9% among men and 49.6% among women (WC > 88 cm). Participants from the urban area showed a significantly higher mean weight, WC, BMI, and blood pressure level, a higher prevalence of obesity and central adiposity compared with those in the rural and pastoralist populations. Resting energy expenditure was highest among the pastoralists and participants from rural areas (results not shown). Fig. 1 shows the prevalence of CVD risk factors among lean, obese and morbidly obese participants for both men and women. The overall prevalence of hypertension was 48.1%, hypercholesterolemia 32.4%, hypertriglyceridemia 20.3%, elevated LDL-C 33.8%, and hyperglycemia 4.6%, respectively. Of the obese participants, 40.5% had formal education and 59.1% lived in the urban area. Participants who received formal education for 9 years or more showed a significantly higher BMI (men, p < 0.001, women p < 0.0001) and a higher prevalence of elevated HBA1c percent ( z 7%) (women 40.0%, p < 0.05). Consumption of
374
M. Njelekela et al. / International Congress Series 1262 (2004) 372–375
Fig. 1. Prevalence of risk factors for CVD among lean (L), obese (O) and morbidly obese (MO) men and women.
a high calorie diet, such as coconut milk and meat for more than 3 days in a week, was higher in the educated group: meat (men 52.7%, p < 0.001; women 30.4%, p < 0.0001) and coconut milk (men 51.9%, p < 0.001; women 32.3%, p < 0.0001), respectively. 5. Discussion The elevated BMI and waist circumference in urban dwellers and among skilled workers indicates that as people become more affluent obesity levels tend to increase [7]. The change in diet structure and acquisition of professional and leisure occupation strongly relate to urbanization [8], which results in a change in CVD risk factor pattern in the urban areas compared with rural areas. In most developing countries, obesity is not yet recognized as a major health problem and resources set for non-communicable disease prevention and treatment are few [1]. The findings of this study attest to an association between obesity with the expected lipid derangements that would constitute part of the predisposition to cardiovascular disease and the metabolic syndrome in urban areas in Africa. Both WC and BMI elevations are commonly associated with dyslipidemia [2,7]. Blood pressure levels and prevalence of hypertension increased with obesity. The
M. Njelekela et al. / International Congress Series 1262 (2004) 372–375
375
association between elevated BMI and hypertension has been reported in another study in Africa [9]. Obesity decreases insulin signal transduction of the insulin receptor leading to insulin resistance [10]. The findings of this study tend to reinforce the fact that diagnosing obesity and identifying an individual and populations at risk requires at most a measuring tape and a weighing scale. The derived BMI and WC allow the identification of ‘‘action points’’ for intervention. The addition of lipid measurements, blood pressure readings and a fasting blood sugar would enable clinical diagnosis of the metabolic syndrome, which should be a target for intensive therapeutic lifestyle changes. Acknowledgements We would like to express our sincere appreciation to our participants and to the Center for Primary Prevention of Cardiovascular Diseases Kyoto for funding this project. References [1] N. Unwin, et al., Noncommunicable diseases in sub-Saharan Africa: where do they feature in the health research agenda? Bull. World Health Organ., Suppl. 79 (2001) 907. [2] P. Poirier, et al., Obesity and cardiovascular disease, Curr. Atheroscler. Rep. 4 (2002) 448 – 453. [3] M.A. Van der Sande, et al., Blood pressure patterns and cardiovascular risk factors in rural and urban Gambian communities, J. Hum. Hypertens. 14 (2000) 489 – 496. [4] P. Bovet, et al., Distribution of blood pressure, body mass index and smoking habits in the urban population of Dar Es Salaam, Tanzania, and associations with economic status, Int. J. Epidemiol. 31 (2002) 240 – 247. [5] M. Njelekela, et al., Prevalence of obesity in middle aged men and women in Tanzania Africa: relationship with resting energy expenditure and dietary factors, J. Nutr. Sci. Vitaminol. 48 (2002) 352 – 358. [6] G.A. Kaplan, J.E. Keil, Socioeconomic factors and cardiovascular disease: a review of the literature, Circulation 88 (1993) 1973 – 1998. [7] R. Martorell, et al., Obesity in women from developing countries, Eur. J. Clin. Nutr. 54 (2000) 247 – 252. [8] B.M. Popkin, The nutrition transition in low-income countries: an emerging crisis, Nutr. Rev. 52 (1994) 285 – 298. [9] F.A. Ukoli, et al., Body fat distribution and other anthropometric blood pressure correlates in a Nigerian urban elderly population, Cent. Afr. J. Med. 41 (1995) 154 – 161. [10] G.L. Dohm, Mechanisms of muscle insulin resistance in obese individuals, Int. J. Sport Nutr. Exerc. Metab. 11 (2001) S64 – S70(Suppl.).