Study design and study population
This was a cross-sectional and prospective study conducted in the Littoral region of Cameroon. The Littoral region is one of the ten administrative regions of Cameroon. The Littoral region is an important economic region in which the economic capital is found. The study was conducted in the urban, semi-urban, and rural areas of the region.
Geographical settings were defined according to the BUCREP criteria [20]. The urban area is characterized by a high population density, mainly composed of civil servants, businessmen, and students, with important infrastructures, and a high level of urbanization. In a rural area, there is no agglomeration of population, the populations for the most part draw their income from agriculture, fishing and breeding. The semi-urban zone is located halfway between urban and rural areas [20].
Sample
The study ran from April to August 2021. Participants were randomly recruited and were of both genders aged 18 years and more residing in the study areas during the study period. Pregnant and lactating women, persons with cardiometabolic diseases, those on medication, and with physical disabilities were not included in our study. The study minimum sample was calculated using the Lorentz formulas with a prevalence of 8.4% of obesity reported by Tachang et al. [21] and the minimum was 120 participants. A total of 879 participants were recruited, and thus constituted, urban: 372, semi-urban: 195 and rural: 312 participants.
Ethics Approval
The study was approved by the Institutional Ethics Committee for Human Health Research of the University of Douala (No CE-UDO/07/2020/T), and by the regional delegation of the Ministry of Public Health. The study was conducted in accordance with the guidelines of the Helsinki Declaration of 1975, as revised in 2008. Also, research authorizations granted to hospital administration staff were obtained. Written informed consents were obtained from all. Data were collected anonymously and were confidential.
Socio-demographic And Behavioral Information
A questionnaire developed from the World Health Organization (WHO) STEPS manual for surveillance of risk factors of NCDs and adapted to the study context was used to collect socio-demographic information (age, level of education, marital status, medication diagnostic cardiometabolic disease…etc.) information on habits related to healthy living, alcohol intake and smoking (answering by “yes” or “no” to the question) in particular; and information about the medical history of study participants. The Alcohol Use Disorders Identification Test (AUDIT) was used to assess the participant’s alcohol consumption.
Parameters Measurements
♣ Anthropometric
Weight and body composition were measured using a bioelectric impedance meter Terraillon Wellness Coach (USA). Height was measured using a measuring tape. The body mass index (BMI) was calculated to assess the degree of obesity of each participant according to the Quetelet formula as the weight (Kg) divided by the square of the height (m2). The participants were classified according to their BMI as follows: normal weight (BMI < 25), overweight (BMI ≥ 25–29.9,) and obese (BMI > 30 kg/m2). Waist circumference (WC) was measured with an inelastic tape between the lower edge of the costal arch and the iliac bone’s upper crest in a standing position with an accuracy of 0.5 cm [22] and waist-to-height ratio (WHtR) was calculated as WC divided by the height.
♣ Blood pressure and heart rate
Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were taken using an electronic blood pressure monitor (JERISON, China) placed on the subject's left arm in a sitting position. The first measurement was taken after a 10 minutes rest in a sitting position and was followed by another measurement after 5 minutes intervals, the average of the two measurements was used to assess the presence or absence of high blood pressure.
♣ Physical activity
Levels of PA were determined based on the Global Physical Activity Questionnaire (GPAQ) analysis guide developed by WHO [23]. This questionnaire comprises 16 questions grouped to capture PA undertaken in different behavioral domains, these are work, transport, and leisure or recreation time during a typical week. GPAQ collects information on the practice of physical activities (frequency, duration, and intensity of activities) and on sedentary behavior. The questionnaire takes into account activities at work, during transport, and leisure activities. The results were scored and participants were classified as having low, moderate and high levels of PA
Biochemistry
For each fasting subject (12–14 hours of fasting), blood glucose was measured between 8 and 10 am using a MyStar Extra glucometer (SANOFI, China). Blood samples were taken from the ulnar vein, and a volume of 10 ml was collected and conserved in EDTA tubes by venepuncture in the hand of each participant. The plasma was obtained by centrifugation at 4000 rpm for 20 minutes in a Techmel & Techmel (USA) centrifuge, then placed in cryotubes and aliquots were frozen at -20°C for further biochemical analyses.
The levels of total cholesterol (TC), HDL-C, and triglycerides (TG) were determined using a UVmini 1240 spectrophotometer (SHIMADZU) according to the Biorex kit material (respectively Cholesterol CHO-Rev 01 of 1271/2008, Triglycerides BXC0271 and HDL CHO-Rev 01 of 1271/2008) [24, 25]. Low-density lipoprotein (LDL) was calculated using the Friedewald et al.[26] formula if the triglycerides are less than 400 mg/dl (4.6 mmol/l). LDL-c was calculated by subtracting HDL-c and VLDL from total cholesterol. The serum standards used for calibration were provided by the manufacturer.
The insulin resistance was assessed by calculating the Homeostatic Model Assessment Insulin resistance (HOMA-IR) using the following
$$\text{H}\text{O}\text{M}\text{A}- \text{I}\text{R} =\frac{[ \text{C}-\text{p}\text{e}\text{p}\text{t}\text{i}\text{d}\text{e} ] \text{x}\text{f}\text{a}\text{s}\text{t}\text{i}\text{n}\text{g} \text{g}\text{l}\text{u}\text{c}\text{o}\text{s}\text{e}}{22.5}$$
The C-peptide blood concentration was determined by ELISA (enzyme-linked immunosorbent assay) using the Mercodia C-peptide Ultrasensitive ELISA test (Mercodia AB Sylveniusgatan 8A SE-754 50 Uppsala, Sweden). The special Mercodia C-peptide ELISA kit is calibrated using the International Reference Reagent for C-peptide, IRR C-peptide 84/510 [27]. The HOMA-IR was evaluated in 600 individuals, 200 per area which were submitted to dosage of C-peptide.
Metabolic Syndrome Criteria
Harmonized definition of MetS by the International Diabetes Federation of 2009 [28] was used whose:
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central obesity that was defined by a waist circumference ≥ 94 cm in men and ≥ 80 cm in women,
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High fasting glucose level ≥ 100 mg/dL (5.6 mmol/L);
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hypertriglyceridemia-serum triglyceride level ≥ 150 mg/dL (1.7 mmol/L);
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Low HDL cholesterol-serum; HDL cholesterol < 40 mg/dL (1.0 mmol/L) in men and < 50 mg/dL (1.3 mmol/L) in females) ;
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High blood pressure [systolic blood pressure (SBP) ≥ 130 mmHg and/or diastolic blood pressure (DBP) ≥ 85 mmHg.
Participants with 3 or more of the 5 MetS components were considered to have MetS.
Statistical analysis
Statistical analysis was performed with the Statistical Package for Social Sciences (SPSS) software, Version 21.0 (SPSS, Inc. Chicago, U.S.A. IBM Corp.). Results of sociodemographic, behavioral information, ponderal status, MetS and its components and level of PA were expressed as proportions (%) for quantitative variables and means ± standard deviation (SD), the distribution pattern of variables was checked. The Chi-2 test was performed to compare unpaired proportions and Student’s t-test on unpaired series was performed to compare quantitative variables between urban, semi-urban and rural areas. Stepwise multivariate analysis was performed to examine the association between the level of PA, MetS and its cluster components, also between geographical settings, MetS and its components. The significance was set with a p-value < 0.05.