Comparison of risk factors for coronary heart disease in a sample of the rural and urban populations of Tanzania with special reference to the level of physical activity

Abstract

Objective To estimate and compare the level of some risk factors for coronary heart disease (CHD) in a sample of the rural and urban populations of Tanzania, with particular reference to the level of physical activity, and the relationships between physical activity level and other coronary risk factors. Design A cross-sectional study to estimate levels of selected coronary risk factors in females and males aged 30 - 60, such as blood pressure, body mass index, obesity, serum lipids, physical activity and percentage of alcohol and tobacco users, and users of several types of diets. Setting The indigenous inhabitants of Temeke - Kigamboni, Tanga - Handeni and Arusha - Monduli districts (rural population), and residents of the city of Dar-Es-Salaam and Morogoro town (urban population). Participants A sample of 985 subjects was surveyed. From the rural area 501 subjects (females: 256, and males: 245), and from the urban area 484 subjects (females: 255, and males: 229) participated in the study. Main outcomes Several rural-urban differences in the observed variables were found in this study. A higher prevalence of a cluster of major CHD risk factors was noted in the urban than vu

in the rural population. The rural population had a significantly higher physical activity level (PAL) than the urban population, i.e. 29.8±15.8 against 16.5± 8.6 kcal/kg/d (mean±SD) (p < 0.001). Both systolic blood pressure (SBP) and diastolic blood pressure (DBP) were significantly lower in the rural than in the urban population, i.e. 129.8±23.8 against 133.5±24.6 mm Hg (p < 0.02), and 77.5±12.7 against 82.1±14.3 mm Hg (mean±SD) (p < 0.001). Prevalence of systolic hypertension, (defined as ~ 140 mm Hg), was found in 31 % - females, and 29% - males of the rural subjects and in 28% - females, and 36% - males of the urban subjects. Prevalence of diastolic hypertension, (defined as ~ 90 mm Hg), was found in 20% - females, and 12% - males of the rural population, and 23% - females, and 29% - males of the urban population. The body mass index (BMI) was significantly lower in the rural population than in the urban population, 22.5±5.0 vs. 27.4±5.6 kg/m'' (mean±SD) (p < 0.001). Prevalence of overweight (defined as BMI ~ 25 kglm2) was found in 22% - females, and 13% - males of the rural population, and 37% - females, and 45% - males of the urban population. Prevalence of obesity (defined as BMI ~ 30 kg/nr') was found in 13% - females, and 7% - males of the rural and 45% - females, and 25% - males of the urban population. Waist and hip circumferences, and waist-to-hip ratio were significantly lower in the rural population, i.e. 73.5 ±19.2, 83.9±22.0 cm, and 0.88±0.1 (mean±SD) (p < 0.001) compared with corresponding values 90.9±12.8, 98.0±11.8 cm, and 0.93±0.1 (mean±SD) (p < 0.001) in the urban population. The rural population had slightly lower serum values of all selected lipids than the urban population. Values in the rural group were: total cholesterol (TC) 3.7±1.1 mmollL, triglycerides (TO) 1.4±0.7 mmollL, high-density lipoprotein cholesterol (HDL-c) 1.0±0.3 mmol/L, low-density Vlll

lipoprotein cholesterol (LDL-c) 2.1±0.9 mmol/L, total cholesterol to high-density lipoprotein cholesterol ratio (TCIHDL-c ratio) 4.2 ±1.8, and free fatty acids (FFA) 0.2±0.2 mmol/L, (mean±SD). Corresponding values in the urban group were: TC 4.5±1.1 mmol/L, TG 1.6±1.1 mmol/L, HDL-c 1.1±0.3 mmol/L, LDL-c 2.7±1.0 mmol/L, TC/HDL-c ratio 4.5±1.6 mmol/L, and FFA 0.3±0.2 mmol/L, (mean±SD). Prevalence ofhypercholesterolemia (defined as TC ~ 5.2 mmol/L) was found in 9 % - females, and 7% - males of the rural, and 22% - females, and 26% - males of the urban population. The PAL was inversely related to most of the selected risk factors ofCHD P<O.OOl). The strongest inverse relationship was between PAL and BM!. In univariate scatter plots, for groups, SBP and DBP blood pressure decreased with increasing PAL, and increased with increasing BM!. For both groups, SBP and DBP blood pressure increased with increasing age, but the increase was steeper for the urban than for the rural group. In multivariate analysis, PAL was a significant negative predictor of several other coronary risk factors, but the apparent influence was low compared to other predictors (p < 0.001). Age, BMI and TG were positive predictors of both SBP and DBP. Overall, cigarette smoking was relatively common in the rural population, i.e. 20% (6% of females, and 31 % of males) against 9%, in the urban population (2% of females, and 14% of males). The prevalence of cigarette smoking was higher among males than females (p < 0.001). Smokeless tobacco use was also prevalent in the rural population: 12% (14% of females, and 11 % of males), but not observed in the urban population. The number of subjects reporting alcohol consumption was lower in the rural population, i.e. 20% (13% of females, and 27% of males) compared to the urban population 27% (17% of females, and 36 % of IX

males) (p <0.01). The major proportion of rural subjects reported either high fat/low carbohydrate intake or low fatlhigh carbohydrate intake, while high fatlhigh carbohydrate seemed to be the main diet pattern of the urban group. Conclusion The fmdings from this population-based survey in Tanzania suggest that urbanization is accompanied by an unfavourable alteration of several coronary risk factors. The urban group had a lower level of physical activity than the rural group, higher blood pressure, body mass index, blood lipids, prevalence of obesity and a higher percentage of subjects reporting high fatlhigh carbohydrate diet. Although the levels of some selected coronary risk factors in the sample of the Tanzanian population were low compared to those reported from studies conducted in western communities, the observed urban-rural differences might be indicative of a progress towards an increase in coronary heart disease, as the population becomes more urbanized. Key words: Coronary, risk factors, physical activity, diet, blood pressure, serum lipids, rural, urban, population, Tanzania, Africa.