CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 2, March/April 2022 AFRICA 53 countrywide prevalence of dyslipidaemia in Nigeria is unknown. Emerging evidence from various sub-national surveys8-10 suggests a high prevalence of dyslipidaemia, in contrast to earlier notions.11,12 However, the reliability of such findings remains contentious, given the small sizes of the populations surveyed. Worse still, the Nigerian population is large and culturally diverse, so much so that only a carefully selected random and representative samplewouldbe suitable to estimate the nationwide prevalence of dyslipidaemia. Efforts to estimate the nationwide prevalence from sub-national data have proven abortive due to heterogeneity in the methods employed, populations studied and dyslipidaemia criteria considered.13 The main objective of this study was to define the prevalence of dyslipidaemia in Nigeria using a representative, nationwide sample. Methods The study population consisted of Nigerians aged 18 years and above who participated in the REMoving the MAsk on Hypertension (REMAH) survey. REMAH was a nationwide survey of NCD risk factors in Nigeria that took place between March 2017 and February 2018. The study design of REMAH has been described in detail elsewhere.14,15 Using a multi-staged sampling technique, subjects were randomly selected from two communities (rural and urban) of a state from each of the six geopolitical zones of Nigeria as follows: Anambra (south-east), Akwa-Ibom (south-south), Oyo (south-west), Federal Capital Territory (north-central), Gombe (north-east) and Zamfara (north-west). The selected communities were mobilised, following which homes were visited and invitations were issued to persons aged 18 years and above. Consenting subjects were invited to a mobile health facility where various physical and clinical examinations were conducted. A total of 4 665 adults were invited, of whom 4 196 subjects consented to participate. However, blood samples were collected from 4 187 subjects, out of which only 3 211 had complete records and also met the criteria for calculating low-density lipoprotein cholesterol (LDL-C) using the Friedewald formula.16 These subjects were considered for analysis (Fig. 1). Before commencement of the study, in each locality, the investigators had a series of meetings with members of the community. During the meetings, the investigators addressed participants’ questions on various aspects of dyslipidaemia and other NCD risk factors. After laboratory analysis of the samples obtained during the field work, the results of the lipid profiles were transmitted to all participants and those who had one form of dyslipidaemia or another were given counselling on lifestyle changes. Those who were judged to need further intervention were referred to the tertiary health institution within the geo-political zone where the local principal investigator representing the zone was a practicing physician. The study complied strictly with the guidelines for research on human subjects as contained in the Helsinki declaration. Approval for the study was obtained from the University of Abuja Teaching Hospital Health Ethics Committee (FCT/ UATH/HREC/PR/041). Non-fasting blood samples were collected and centrifuged within 45 minutes of collection, following which the resulting sera were stored at –20°C for later analysis. Serum lipids, including total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) were analysed on a Landwind c100 auto chemistry analyser, using direct,17 endpoint18 and multilayer element19 methods, respectively, with the aid of test kits procured from Beijing Strong Biotechnologies Incorporations. LDL-C levels of samples with TG < 4.5 mmol/l were calculated using the Friedewald formula.16 Dyslipidaemia was defined according to the criteria of the WorldHealthOrganisation (WHO).20 A subject was considered to have elevated TC, otherwise referred to as hypercholesterolaemia (h-CHL), if TC was > 5.1 mmol/l; elevated TG, otherwise referred to as hypertriglyceridaemia (h-TG), if TG was > 1.7 mmol/l; elevated LDL-C (e-LDL) if LDL-C was > 3.5 mmol/l; or low HDL-C (l-HDL) if HDL-C was < 1 mmol/l for women or < 0.9 mmol/l for men. Trained field workers administered a modified WHO-STEPS questionnaire to obtain information on subjects’ demographics, lifestyle characteristics, and history of hypertension and diabetes mellitus. In accordance with the guidelines of the European Society of Hypertension,21 five consecutive blood pressure measurements were obtained from subjects in a sitting position using a mercury sphygmomanometer. The mean of the five readings was calculated as systolic and diastolic blood pressures. Height and weight were measured using a stadiometer to the nearest 0.1 cm and 0.1 kg, respectively. Measurements were taken while subjects were lightly clothed, barefoot and without head gear. Body mass index (BMI) was calculated as the weight (kg) per unit height squared (m2). Waist circumference was measured using a non-stretchable measuring tape, as the minimum horizontal distance midway between the iliac crest and the lower costal margin. Hip circumference was measured as the maximum horizontal distance around the buttocks. Subjects invited = 4 665 Subjects who declined = 469 Subjects recruited = 4 196 Subjects without blood samples = 9 Subjects with blood samples = 4 187 Subjects without complete records = 859 Subjects with complete records = 3 328 Samples with TG < 4.5 mmol/l = 117 No. of samples analyzed = 3 211 Fig. 1. The study flow.
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