SA JOURNAL OF DIABETES & VASCULAR DISEASE RESEARCH ARTICLE VOLUME 19 NUMBER 1 • July 2022 5 Methods A cross-sectional study using a complex multi-stage cluster sampling method was used to recruit 1 000 participants in the city of Gaborone and surrounding villages. The target population included Batswana men and women aged between 25 and 65 years residing in Gaborone, Tlokweng and Mogoditshane. Data were collected at shopping malls where people of heterogeneous characteristics converge. A total of 37 shopping malls were classified as either a super mall or satellite mall across Gaborone and the two villages. A total of seven malls were randomly selected for the study. The International Diabetes Federation (IDF) Africa region14 reports an estimated diabetes prevalence of approximately 4% among Batswana adults. Since the required sample size will increase with higher population prevalence, a prevalence of 8% among the 25- to 65-year cohort was assumed. d2 Z2 (1-α/2)P(1–P) = where d is the margin of error, P the prevalence level and Z the normal score corresponding to the (1–α) % confidence level. With a 5% type I error and assumed 8% diabetes prevalence in Botswana, the sample was calculated at = 452. With cognisance of the cluster sampling method being employed, the correlated responses were accounted for. A design effect of two was applied, which doubled the sample size to 904. Furthermore, some critical questions on anthropometric measures may not have been available for some respondents due to refusal and/or nonresponse. Assuming a refusal rate of 10%, the final sample size used was 1 000. A sampling frame of all shopping malls in Gaborone and surrounding villages of Tlokweng and Mogoditshane was compiled and a sample was randomly selected from the list. In the selected malls, shoppers were recruited as they passed by the testing area. The recruitment was alternated between a stratifying variable, gender, to ensure a balance between male and female participants. Once eligibility had been established and consent to participate had been obtained, the participants were enrolled in the study. Ethical approval was obtained from the institutional review boards of both the University of Botswana and Stellenbosch University (ref #: IRB0005239), as well as from the Ministry of Health, Botswana (ref # HRU 00806). Data were collected from volunteers who agreed to participate in the study after an introduction and briefing on the study intent. Following written, informed consent, a total of 800 volunteers were recruited, interviewed and assessed. Data collection included demographic, anthropometric, biochemical and behavioural factors. All procedures specified by the Health Professions Council of Botswana as good clinical practices were strictly adhered to. Demographic data included questions related to gender, age, level of education, marital and work status, number of people above 18 years in the household and average annual earnings. Medical history included questions related to history of elevated blood pressure (BP), diabetes, TC and CVDs. Resting BP, height and weight, and waist and hip circumferences were measured and recorded. Biochemical measures gathered data related to BG and blood lipids [TC, triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C)]. BP measurements were taken using an automated BP monitor (OMRON Intelli Sense M3W) after a five-minute rest following the interview. Waist and hip circumferences were measured using a SECA measuring tape (201 cm) according to the International Society for the Advancement of Kinanthropometry (ISAK) standard guidelines.15 Height was measured with a portable SECA stadiometer using the free-standing method with the head placed in the Frankfort plane, and weight was measured with the SECA Alpha digital scale (model 770). Capillary BG, TG and TC were assessed with the finger-prick test with the Care Sense N BG monitoring system, while blood lipids were measured using the Cardio Check PA system. Although several definitions are formulated for the MetS,16-18 the IDF is considered more relevant for the African context.19 We therefore classified participants as having the MetS using the IDF criterion where central obesity (defined as waist circumference ≥ 94 cm for men and ≥ 80 cm for the women was indicated, with ethnicspecific values for other groups), and any two of the following four; raised levels of TG ≥ 3.9 mmol/l, low HDL-C levels (men < 1.0 mmol/l; women < 1.3 mmol/l) or on dyslipidaemia medication, elevated BG ≥ 5.6 mmol/l or on diabetes medication, or elevated BP ≥ 130/85 mmHg or on HTN medication. Statistical analysis Statistical analysis was conducted using Statistical Package for Social Sciences (SPSS version 22). Most of the variables analysed for this output were quantitative, hence we report their means ± standard deviations. All variables tested were contrasted by gender using Student’s t-tests. Contrasts for proportions among subpopulations were performed using homogeneity chi-squared tests. A significant difference was accepted if p-values were less than 0.05 for both tests. Results A total of 800 respondents participated in the study drawn from seven shopping malls, yielding an 80% response rate. From the 800 participants, 664 were selected from malls in Gaborone and the remaining 136 from Tlokweng and Mogoditshane. The results are based on the 756 participants (363 men and 393 women) who had complete data for all variables. Therewereno significant differences for age,waist circumference, diastolic BP, BG and TG between genders (Table 1). There was a significant gender effect observed for body mass index (BMI) (p < 0.001), hip circumference (p < 0.001), waist–hip ratio (p < 0.001), systolic BP (p < 0.001) and HDL-C (p < 0.001). Women presented with a higher BMI (34.4 vs 13.0%) and waist circumference (45.5 vs 11.0%), and low HDL-C levels (50.0 vs 48.7%), while the men had higher systolic BP (50.3 vs 39.4%). Overall prevalence of the MetS was estimated at 32.7%. The prevalence was higher among women at 44.5% versus men at 20.0% (Table 1). Overall, low HDL-C levels identified the highest candidates for the MetS at a prevalence of 49.4%, followed by waist circumference (47.9%), TG (47.4%) and elevated BP (44.7%) (Table 1). The oldest age group (55–65-year-olds) had the highest prevalence of the MetS, with men having 52.9% and women 61.5% (Table 2). The MetS prevalence increased with age among men, from 26.6% in the 25–34 age group, 41.3% in the 35–44 age group, 46.7% in the 45–54 age group and 52.9% in the 55–65 age group. A similar trend was observed in the women, with the prevalence increasing from 39.0% in the 25–34 age group,
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