CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 5, September/October 2022 AFRICA 235 Several studies have also reported that chronic low-grade inflammation is associated with MA and the risk of atherosclerosis.16-18 Furthermore, MA was also found to be associated with serum total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C).19,20 Contradicting results wherein MA was not associated with CRP, IL-6 21,22 and serum lipids23 have been reported. Some studies have attributed the contradiction of associations to differences in the study approach, the method of diagnosing MA, control for confounders, or differences in sample size.21,23 Although, the mechanism leading to MA is unclear, the literature documents that endothelial dysfunction may be responsible.24 Associations of endothelial dysfunction with MA,25 dyslipidaemia26 and low-grade inflammation27 have long been reported among patients with conditions such as hyperlipidaemia. MA, together with low-grade inflammation and dyslipidaemia, are the risk factors for CVDs.28-30 Hence, the hypothesis that high levels of serum lipids and inflammatory markers are associated with MA. MA has been reported to be more prevalent in blacks compared to whites in an American population.31,32 This is thought to be due to socio-economic discrepancies, access to healthcare, differences in glycaemic control, or a possible biological or genetic difference in the populations.32 This makes the investigation of MA in a black population essential. Despite the current burden of NCDs, including CVDs, in South Africa,33 there is a paucity of data on the prevalence of MA in the black South African population. Globally, most studies on MA focused separately on either MA and inflammatory markers or MA and serum lipids. As a result, not many studies have reported on the association among these three cardiovascular risk factors. This study was undertaken to determine the prevalence of MA among a presumably healthy black population, and further to determine the association of MA with inflammatory markers and serum lipids. It is noteworthy that MA, together with an evaluation of inflammatory markers and serum lipids, may have a potential role in improving cardiovascular risk prediction. Methods A cross-sectional study using a quantitative method was conducted in a rural black population to determine the association of inflammatory markers and serum lipids with MA. This study is part of a larger study titled ‘Prevention, control and integrated management of chronic diseases in a rural black population, South Africa’. The larger study aimed to identify specific risk factors for chronic diseases in a rural settlement in the Limpopo province, South Africa. The study used a WHO STEPS questionnaire to gather information on socio-economic status and risk factors for NCDs with questions covering different cardiovascular risk factors.8 The study setting has previously been reported by Alberts et al.34 The study was conducted in the Dikgale Health and Demographic Surveillance System (DHDSS) site, a rural site in the Limpopo Province of South Africa, situated approximately 40 km north-east of Polokwane, the capital of Limpopo Province. The area constitutes communities typically made up of households clustered in villages with a population of approximately 36 000, speaking the local language of Sepedi. In 2009, the site was enlarged from eight to 15 villages. The area has poor infrastructure with minimal use of available electricity and shared or communal taps for water supply.34 The site has a socioeconomic status characterised by high rates of unemployment and singlehood, and low rates of tertiary education.35-38 These living conditions are consistent with the findings of the South African National Health and Nutrition Examination Survey (SANHANES-1).39 In a larger study, 2 981 participants were selected randomly from the DHSSS database. Only participants aged 18 years old and above were selected to participate in the study. Of the 2 981, only 1 407 participants completed the WHO STEPS questionnaire, of whom 878 were women and 525 were men. Only 817 of the participants were available to donate fasting blood samples. Reasons for the low participation were leaving for work early in the morning, unavailability after repeated visits, refusal to participate, death or emigration.35 The WHO STEPS questionnaire was first translated into Sepedi (a local language), and the field workers were then trained in the administration and understanding of the questionnaire during a pilot study to pre-test its feasibility among participants who did not form part of the main study. The current study included participants who gave written consent to take part in the study, completed the WHO STEPS questionnaire, and gave both blood and urine samples. The study excluded participants with albumin/creatinine ratio (ACR) > 2.5 mg/mmol in males and > 3.5 mg/mmol in females,40 and participants with confounders such as renal disease (serum creatinine of ≥ 170 µmol/l), diabetes (glucose of ≥ 7.0 mmol/l and/or history of diabetes), pregnant women and HIV-positive participants. Furthermore, participants who were on medication for diabetes and HIV, or using lipid-lowering drugs were excluded to avoid interference with serum lipids. The final sample of 602 participants was obtained. As part of the larger study, a spot urine sample was collected into a sterile urine jar from each participant. Blood was collected in silica-coated vacutainer tubes, EDTA-containing tubes and sodium fluoride tubes. Blood samples were centrifuged and immediately after centrifugation, serum lipids, hs-CRP, glucose, insulin, HIV status and creatinine were determined. The remaining serum was stored in cryotubes at –80°C for further determination of IL-6. The frozen samples were aliquoted to minimise freeze–thaw cycles on individual tubes, thus preserving the sample quality and integrity. Serum hs-CRP levels were measured using the IMMAGE 800 immunochemistry system. Insulin and IL-6 were determined using the ACCESS 2 chemistry system. Serum lipid (TG, cholesterol, HDL-C and LDL-C) and glucose levels were determined using the ILAB 300 plus chemistry system. Spot morning urine samples were collected using a sterile urine jar. Urine creatinine and albumin concentrations were measured using the ILAB 300 plus chemistry system and the ACR was calculated. Subjects with an ACR of 2.5–25 mg/mmol in males and 3.5–35 mg/mmol in females40 were considered microalbuminuric and subjects with an ACR of < 2.5 mg/mmol in males and < 3.5 mg/mmol in females were considered normoalbuminuric (NA). Subjects with MA were regarded as the cases and subjects with NA were regarded as controls for this study. Anthropometry (weight, height and waist circumferences) were all measured according to the WHO procedures. Weight was measured using a calibrated smart D-quip electronic scale
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