Sex and area differences in the association between adiposity and lipid profile in Sub-Saharan Africa: A comparison with a European population

Abstract

Introduction Sub-Saharan African (SSA) countries are facing a rising epidemic of non-communicable diseases (NCDs) alongside a persistent burden from undernutrition and infectious diseases. Mendelian randomization (using genetic variants as instrumental variables) and randomised controlled trial (RCT) evidence show that high levels of total (TC) and low-density lipoprotein-cholesterol (LDL-C) and of triglycerides (TG) are key causal risk factors for coronary heart diseases (CHD), that can be effectively modified to prevent CHD. Studies in high-income countries show that higher adiposity results in an adverse lipid profile, but whether this association is similar in SSA populations is unclear. One previous small study from Cameroon suggested higher adiposity increased dyslipidaemia in urban dwelling SSA populations but not in those in rural areas, but to our knowledge previous studies have not sought to replicate this. This study aimed to (i) assess the association between total and central adiposity measures and lipid profile in Malawi, exploring differences by sex and area of residence and (ii) compare the associations with observations from a predominantly white European-origin population cohort from the United Kingdom (UK). Methods Baseline data from the Malawi Epidemiology and Intervention Research Unit Non-Communicable Disease study (MEIRU NCD) were used. The study assessed adults in a rural (Karonga, Northern Malawi; n = 12,153) and an urban (area 25 of Lilongwe, the capital city; n= 12,869) of Malawi. The association of body mass index (BMI) and waist-hip ratio (WHR) with fasting lipids [TC, LDL-C, high density lipoprotein-cholesterol (HDL-C) and TG] was assessed by area and sex. Data from the UK Avon Longitudinal Study of Parents and Children (ALSPAC) were used for the comparison with a population from a high-income European setting, and included 3286 adolescents (mean age 17.8), 4107 mothers (mean age 47.9), and 1933 fathers (mean age 53.3). Multiple linear regression was used to examine the association of both BMI and WHR with each lipid measure, adjusted initially for age and then for potential confounding by household assets, education, marital status, number of children, smoking, alcohol, physical activity, lipid-lowering medication, and HIV status. As the UK data were taken from largely urban/sub-urban dwelling adolescents and middle-aged females and males, we selected two age groups of participants from the urban group of the Malawi cohort that had similar age distributions to the UK cohorts to compare associations between Malawians and UK residents. Results We observed positive linear associations of BMI and WHR with TC, LDL-C and TG and inverse association with HDL-C. Associations between BMI/WHR and serum lipids were in general similar in females and males, however, differed by area, with the associations between BMI and all serum lipids being stronger in rural than urban females, except for HDL-C, which was stronger in urban females. Associations did not differ consistently between rural and urban male residents. Associations of BMI and WHR with lipids were mostly similar or weaker in Malawi than the UK urban residents in both sexes and age groups. However, in middle-aged males, there was some evidence that associations of BMI and WHR with TC and LDL-C were stronger in Malawians. Conclusions The consistent associations observed of higher adiposity with adverse lipid profiles in females and males living in rural and urban areas of Malawi highlight the emerging adverse cardio-metabolic epidemic in this poor population. The similarity (or even stronger) associations between the Malawian and UK population highlight the importance of early interventions to control the emerging obesity epidemic in SSA populations.