The study was a cross-sectional, community-based epidemiological study using stratified cluster sampling design conducted in rural Kuseki village in Kuje area council and urban Garki in Abuja Municipal Area Council both in the Federal Capital Territory (FCT), Abuja, Nigeria from August- December, 2010. These populations were the original natives of the area that now bears the FCT. The study area was divided into approximately four equal sectors using the electoral list. The minimum sample size of 174 (in each location) was derived from the formulae n = Z2pq/d2 where n = minimum sample size, z = confidence limits = 1.96 (95% confidence level), p = prevalence of metabolic syndrome in Abuja (13%) [18], q = 1-p and d = degree of accuracy (0.05). We however chose a sample above the minimum to increase the power of the study and to allow for non-response.
The first house was randomly decided and thereafter every tenth house was taken for the study. If the chosen residents were unwilling to participate in the study, or not a native Abuja resident, the adjacent house was selected. All members of the household with age less than 18 years as well as pregnant women were excluded from the study. The eligible residents in the selected houses were recruited. If desired number of subjects could not be included and the end of the area was reached, investigators returned back to the starting point and the above procedure was repeated until all the remaining subjects were enrolled. The same procedure was applied in all the sectors and sites. All subjects had their sociodemographic variables recorded. They were also assessed for smoking and alcohol consumption. All the subjects were fully informed about the purpose of the study and a written informed consent was obtained from each of them. Approval for the study was obtained from the health research and ethics committee of both local governments as well as the University of Markudi, Benue state, Nigeria.
Anthropometric measurements
Body weight (to nearest 0.1 kg) and height (to nearest 0.1 cm) were measured while subjects were dressed in light clothing and stood erect with bare foot and eyes directed straight ahead. Body mass index (BMI) was calculated as weight (kg)/ height (m)2. Waist circumference (WC) was measured midway between iliac crest. The skinfolds (biceps, triceps, subscapular, suprailiac and abdominal) thickness were measured using Lange skinfold calipers by the same physician (OSA). The sum of all skinfolds (S5SF), central (sum of subscapular skinfold, suprailiac skinfold and abdominal skin fold) and peripheral skinfolds (sum of biceps skinfold and triceps skinfold) were calculated.
Measurement of percentage body Fat and blood pressure
The percentage body fat (%BF) was estimated using Deurenberg formulae [19] Blood pressure and resting heart rate measurements. Participants were seated for at least 5 min before the diastolic blood pressure (DBP), systolic blood pressures (SBP) and resting heart rate (RHR) were measured on the left arm with arcusson mercury sphygmomanometer. The average of three consecutive measurements was taken as the mean systolic and diastolic blood pressure. To define high levels of blood pressure the recent criteria recommended by the WHO were used; hypertension: SBP of 140 mm Hg and/or DBP of 90 mmHg, or use of blood pressure lowering drugs.
Biochemical measurements
A fasting venous blood sample was obtained after anthropometry and physical examination for blood glucose and lipid profile. Estimation of total cholesterol (TC), serum triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C), was performed on the sample drawn after 12 hour overnight fast. TC was estimated with the ferric chloride method [20]. The method described by Rosenberg and Gottfried [21] was used for the determination of TG. After precipitation of very low-density lipoprotein cholesterol and low-density lipoprotein cholesterol (LDL-C) from the serum by phosphotungstic acid and magnesium chloride, the supernatant was taken and HDL-C estimation performed by the method described for TC. The value of LDL-C was calculated using Friedwald’s equation [22].
Definitions
BMI, WC and %BF categories were determined according to WHO criteria, with overweight defined as BMI = 25–29.9 kg/m2; WC = 80–87.9 cm in women and WC = 94-101.9 cm in men; and obesity as BMI >30 kg/m2; WC > 88 cm in women and WC >102 cm in men [23, 24]; For BF%, over weight was defined as BF = 33-39% in women and BF = 21-27% in men, and obesity as BF > 39% in women and BF > 27% in men [23]. Further, S5SF ≥50 mm was taken as high. Impaired fasting glucose (FBS ≥ 6.1 mmol/L) and diabetes (FBS ≥ 7.0 mmol/L) were diagnosed according to the WHO criteria [25]. The National Cholesterol Education Program Adult Treatment Panel III criteria was used to define dyslipidaemia (Total cholesterol ≥ 5.1 mmol/L, triglycerides ≥ 1.7 mmol/L, LDL-C ≥ 3.3 mmol/L and HDL-C ≤ 1.0 mmol/L) [26].
Statistical methods
Data were recorded on a pre-designed proforma and latter entered into a SPSS spreadsheet. For the variables following approximate normal distribution, mean and standard deviation (SD) were computed, while categorical variables were expressed as frequencies and percentages. Student’s t-test was used to compare the mean values in the two independent groups while categorical variables were compared using pearson chi square test. Correlations between variables were analyzed using the non-parametric spearman rank order test. A multivariate regression analysis was conducted to determine the anthropometric predictors of systolic blood pressure in the simultaneous context of other covariates. The variables entered into the multiple linear regression models were those that showed an association on bivariate analysis. A p-value of ≤ 0.05 was considered statistically significant. Statistical Package for Social Sciences 16.0 (SPSS) was used for statistical analysis.
