Prevalence and Association of Conventional and Novel Risk Factors for Coronary Heart Disease in Langata Constituency,Nairobi,Kenya

Abstract

Therehas been considerable progress in the understanding of conventional risk factors for cardiovasculardisease such as cigarette smoking, hypertension, hyperlipideamia and diabetes. Howeverthey do not fully account for cardiovascular disease-associated complications. As a result,novel risk factors such as C-reactive protein (CRP) and homocysteine have come under investigation.The aim of this study was to determine the prevalence and interrelation of conventionaland novel risk factors for coronary heart disease among an urban population in Kenya.This was a cross-sectional study carried out in Langata Constituency of Nairobi County. Thedesign was based on a three-stage cluster sampling methodology. The first stage involved randomselection of 30 clusters, followed by random selection of households within the clusters, andfinallyselection of r~pondents from the households. Permission to carry out this study was grantedby Kenya Medical Research InstitutelNational Ethical Review Committee and Kenyatta University. Information on demographics and behavioural habits was collected using a structured questionnaire.Body composition was determined based on measurements of height and weight, anda general clinical examination performed including blood pressure check. Biochemical measurementsincluded fasting blood glucose, homocysteine, CRP and the lipid profile. Data wasweighted and analyzed using SPSS 16.0 with values of p< 0.05 considered statistically significantR. esults were expressed as mean ±SD or as proportions (%). Unpaired t-test was used forcontinuous normally distributed variables and Chi-square test and Fisher's exact probability forcategorical variables. Linear associations were calculated using the Spearman's correlation coefficientand the odds ratios calculated using EPI info 6. A total of 539 adults (m: 299; w: 240) withmeanage of 38.09 ± 13.4 years participated. Pre~alence of homocysteine> 12)lmol/L, CRP >5mg/L,diabetes, high blood pressure and obesity was 42.7%, 18.4%, 9.5%, 50.2% and 16.3% respectively.Homocysteine was significantly associated with increasing blood pressure (AOR 6.3[95%CI 1.5-6.3]; p=0.002J, and obesity (AOR 0.15 [95% CI 0.06-0.4]; p<0.001). CRP was significantly associated with obesity -&<'0,.001). Both homo cysteine and CRP recorded high specificity and negative predictive value to conventional risk markers of CHD. Based on the Framingham risk scores, the proportion.of women with<l %, 1%, 2%, 3%, 4%, 5%, 6%, 8%, 11%,14%,17% 10-year risk of developing hard coronary heart disease event was 67.3%, 15.2%, 3.9%,2.7%,3%, 1.8%, 1.5%, 1.5%, 1.5%, 0.9% and 0.3% respectively. The proportion of men with<1%,1%,2%,3%,4%,5%,6%,8%,10%,12%,16%,20%,25% and ~30% 10-year risk of developingMI or CHD was 33.1%,18.4%,7.4%,4.3%,4.3%,3.7%,5.5%,6.1%,7.4%,3.1%, 1.8%,3.1%,1.2% and 0.6% respectively. In conclusion, the prevalence of coronary heart disease risk factors remains high in this urban Kenyan population. High blood pressure and dyslipideamiaare the major contributors to the overall risk as evidenced by the strong dyslipideamic rather than diabetic risk profile. The coexistence of hyperhomocysteineamia with . other coronary heart disease risk factors positions homo-cysteine as a potential prevention intervention target in this study population. Addition of homo-cysteine and CRP to conventional risk factors may result in small increases in the ability to classify risk.