Study population
This is an analysis of inclusion data collected in the TAnve HEalth Study (TAHES) a prospective population-based cohort study initiated in 2015 in Tanve, a rural setting 150 km north of Cotonou, the capital of Benin. The TAHES involved all adults above 25 years old living in Tanve(9). Its main objective is to assess the frequency of CVDs and their associated risk factors. Exclusion criteria were pregnant women and refusals to participate.
All participants and/or their families gave informed consent prior to inclusion in the study. Written consent was obtained whenever feasible. For illiterate people, the study’s objectives were verbally explained and consent was obtained by thumbprint.
The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki and had prior approval of the Benin national health's research ethics committee and the “Comité de Protection des Personnes du Sud-Ouest et d’Outre-Mer 4 in France”.
Data collection
An exhaustive sampling using a door-to-door approach was performed. Data were collected by 8 teams of 3 trained investigators, using a questionnaire adapted from WHO STEPS tools(10) in the households.
Sociodemographic data
Sociodemographic data included age, sex, marital status (never married, living with someone as a couple, widow/divorced/separated), education (none, primary education, higher), profession (employee/government employee, craftsman/ storekeeper, farmer/breeder/fisherman, homemade/retired, jobless), and the household income per month (low, middle, high) according to the World Bank indicators(11).
Cardiovascular risk factors
The cardiovascular risk factors were defined according to the WHO STEPS surveillance manual(12). Tobacco use was assessed and participants were classified as never users and current/former users (including cigarette, cigar, pipe or other modes of tobacco use including chewing tobacco).
Weight was measured to the nearest 100 g on mechanical scales (Seca, Hamburg, Germany) and height was measured to the nearest centimeter using a carpenter meter. While the stand upright position was impossible, height was estimated according to the knee height (KH) using Chumlea’s formula for non-Hispanic Black people. Body mass index (BMI) was calculated as weight/height². Underweight was defined as BMI <18.5 kg/m², normal weight: BMI= 18.5-24.9 kg/m², overweight: BMI= 25-29.9 kg/m², and obese BMI ≥ 30 kg/m².
Diabetes was defined as currently taking antidiabetic drugs or having a fasting capillary whole blood glucose value³ 126 mg/dL(13).
Blood pressure measurements and HTN definition
Systolic (SBP) and diastolic (DBP) blood pressures were recorded, in seated position, after a rest of at least 15 minutes, using an electronic device (OMRON® M3, OMRON Corporation, Japan). Three measures were recorded, in both arms, at 5-minutes intervals. In accordance to the 2017 ESC Guidelines on hypertension the average of the last two measurements was used in the analyses and hypertensive subjects was defined by self-reporting ongoing treatment, or SBP ³140 mm Hg and/or DBP ³90 mm Hg (14). The hypertension was defined as controlled when SBP <140 mm Hg and DBP <90 mm Hg under pharmacological treatment.
Other Data
Nutritional variables included the dietary sodium intake using a food frequency questionnaire(15) and defined according to the WHO guidelines for sodium intake(16).
“Rare” salt intake was defined by low-salt food intake, seasoning less than once a day and consuming ready-made-dishes less than twice a week.
Low intake of fruit and vegetable was defined as consuming less than five total servings (400 g) of fruit and vegetables per day.
Harmful (moderate to heavy) use of alcohol was defined as consumption of >60 g of alcohol for men or 40 g for women in one occasion within the last 30 day. Consumption below these thresholds was considered as light.
Sedentary lifestyle was defined as <150 min of moderate-intensity activity (walk, bicycle) per week, or equivalent.
Data Analysis
Descriptive analyses were performed to compare the socio-demographic, cardiovascular risk factors and nutritional variables in men and women. The averages (±SD) and numbers (ratios) were compared with Fisher’s exact test and the Chi-square test, as appropriate.
The association between variables and HTN was assessed by univariable and multivariable analyses. A multivariable logistic regression model was performed to identify associated factors for HTN within demographic variables and CVD risk factors when p-value <0.20 in univariable logistic regression. Interactions between independent variables in the final model were examined.
We performed several models. In these models, age and sex were forced systematically.
First, we adjusted for sociodemographic factors such as age, sex, country, area, marital status, and previous occupation (model 1). Second, cardiovascular risk factors — tobacco use, BMI, physical activity, diabetes — were additionally adjusted (Model 2).
Third, nutritional factors (salt consumption and alcohol consumption, fruits a,d vegetables) were also adjusted for (Model 3).
The level of significance was fixed at 0.05 for all analyses. Statistical analyses were carried out using Statview 5.0 software (SAS Institute,Cary, USA).