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