A secondary cross-sectional analysis was performed using data from the WHO STEPS  survey conducted in Burkina Faso in 2013. This study is a recommended tool for surveillance of chronic diseases and their risk factors in WHO member countries. The survey is a standardized method to collect, analyse and disseminate data. It is a sequential process that starts with gathering key information about risk factors with a questionnaire; subsequently and simple physical measurements and are collected. The WHO STEPS includes a representative sample of the study population, which allows the results to be generalizable to the entire population .
The study population was adults of both sexes aged between 25 and 64 years who had been living in Burkina Faso for at least six months on the day of the survey.
Sample size and data collection
The total sample size calculation and the data collection process throughout the country have been described by Soubeiga et al. in previous publication in BMC Public Health . The calculation was based on the prevalence of hypertension as primary outcome, and was estimated at 29.6% (IC95%: 27.3-31.9). The nationally-representative sample size, based on 20% non-response, was estimated as 4785 (rounded up to 4800) adults aged 25–64 years.
Since the national adult rate of those who ever been screened for hypertension was previously unknown, if it the approximative LMICs’ rate was assumed (at about 1/3) , the sample size would roughly be identical.
Data collection was conducted from 3 September to 24 October 2013 and household sociodemographic information was recorded via face-to-face interviews in the language spoken by the participant after BP and anthropometric measurements were collected.
Variables of interest extracted from the STEPS survey database
The participants’ demographic variables included gender, residence (rural, urban), age (25–64 years), marital status (grouped into i) married or cohabitating, ii) single), education level (grouped into i) no formal schooling, ii) primary school and iii) secondary or higher), and occupation (grouped into i) public or private formal employment, ii) employment without or with uncertain income, such as students, housekeepers or unemployed).
The STEPS questionnaire included the yes/no question on being ever screened for hypertension, and was: “Did a doctor or other health professional ever measure your BP?”.
Physical measurements: Anthropometric characteristics were weight (kg), height (m), BMI (weigh/height², kg/m²) and waist circumference (WC in cm). Height was measured to the nearest 0.1 cm using a stadiometer (SECA 214) on a subject without shoes while weight was measured to the nearest 0.1 kg with a personal scale (SECA 813) on a lightly clothed subject without shoes. Waist circumference was measured to the nearest 0.1 cm (as per WHO recommendations) with a measuring tape (SECA 203) at the midpoint between the last rib and the iliac crest, with the subjects standing upright and breathing normally. The BMI was used to characterize underweight (BMI<18.5 kg/m²), normal (BMI=18.5 – 24.9 kg/m²) overweight (BMI=25 – 29.9 kg/m²) and global obesity (BMI ≥30 kg/m²) states, and thus, BMI≥25 kg/m² defined overweight/obesity . The WC was used to characterize abdominal obesity. Recently, the African Partnership for Chronic Disease Research (APCDR) specifically recommends the cut-offs of 81.2/81.0 cm for detecting abdominal obesity in men/women in SSA , while the cut-offs of 94/80 cm for men/women were previously recommended by the International Diabetes Federation (IDF) .
Systolic blood pressure (SBP in mmHg), and diastolic blood pressure (DBP in mmHg) values were measured three times using a mobile device (CardioChek™ 1708 PA, Indiana, United States of America), with their mean value being used in the analysis. Individuals with mean values of SBP/DBP <120/80 mmHg were considered normotensive, those with SBP between 120 – 139 mmHg and/or DBP between 80–89 mmHg were considered prehypertensive, while those with SBP/DBP≥140/90 mmHg and/or medication as hypertensive .
All measurement devices were provided by the WHO and were carried out on the same day.
Participants included in the analyses
After data collection, 105 individuals were not eligible or had invalid data regarding sex, 10 had missing data on marital status or education level, 649 did not provide response to the yes/no question on “ever being or not screened for hypertension” while 61 and 144 participants did not have valid data on BP and anthropometric parameters respectively. In total, 3831 participants were included in the analyses.
StataCorp™ Stata Statistical Software for Windows (Version 14.0, College Station, Texas, United States of America) was used to analyse the data. The quantitative variables are expressed as the means±standard deviations, and the qualitative variables are expressed as percentages (%) with 95% conﬁdence intervals (CIs). Student’s t test was used to compare quantitative variables, and the chi-square test was used to compare categorical variables. We used the both cut-offs of APCDR and IDF to describe and compare abdominal obesity. Logistic regression analysis was performed using “ever been screened for hypertension” (from the binary item, yes/no response) as the outcome, while the overweight/obesity state and abdominal obesity (according to the APCDR cut-offs) were explanatory variables, and all the six sociodemographic factors were the variables for adjustment. We proceeded by a progressive elimination of factors by decreasing the order of significance, i.e., with high level of the p-value. For all analyses, a p-value less than 5% was considered significant.
All methods were performed in accordance with the relevant guidelines and regulations and the protocol of the STEPS survey was approved by the Ethics Committee for Health Research of the Ministry of Health (deliberation No: 2012-12092; December 05, 2012). All participants provided written informed consent to participate and were made aware of their possibility to voluntarily terminate their participation at any time.