Relative contribution of vitamin D deficiency to subclinical atherosclerosis in Indian context: Preliminary findings

Asian Indians have a genetic predisposition to atherothrombotic risk. common carotid intima-media thickness (CCIMT) measured by ultrasound is a quantitative marker for atherosclerotic burden and a derived variable, that is, “CCIMT statistical Z-score (Z-score)” is useful for better quantification. The association between vitamin D deficiency and atherosclerosis is inconclusive. Since, vitamin D deficiency is highly prevalent in India, there is a need to study its relative contribution to subclinical atherosclerotic burden. This prospective cross-sectional study (n = 117) in apparently healthy individuals aged 20 to 60 years sought to identify the determinants of CCIMT Z score with CCIMT measured by “echo-tracking” method. A multivariable linear regression analysis was done with CCIMT Z score as dependent variable and the following as independent variables: age, body mass index, waist-to-height ratio, total cholesterol to HDL ratio (TC-HDL ratio), serum vitamin D3 levels (ng/mL), sex, diabetes mellitus, current cigarette smoking status. A diagnostic prediction model was also developed with a threshold value of 1.96 for CCIMT Z score. The mean (SD) for calendar age (y) was 40 (8). There were 26 (22.22%) individuals in sample with CCIMT Z score ≥1.96 (advanced stage) of whom 14 (23.33%) were <40 y (n = 60). The mean score was 1.28 (90th percentile) in the entire sample. Vitamin D3 deficiency with a mean (SD) blood level (ng/mL) of 14.3 (6.4) was noted and prevalence of deficiency was 81%. The final model was CCIMT Z-score = 0.80 + (0.841 × current smoking = 1) + (0.156 × TC-HDL ratio) – (0.0263 × vitamin D3 blood level in ng/mL). The decreasing order of association is smoking, TC-HDL ratio, and vitamin D3. With the model, likelihood ratio (95% CIs) was better for positive test 3.5 (1.23–9.94) than that for a negative test 0.83 (0.66–1.02). Internal validation with Bootstrap resampling revealed stability of baseline diagnostic variables. There is substantial subclinical atherosclerotic burden in Indian setting with independent contribution by vitamin D deficiency. The model is valuable in “ruling-in” of the underlying advanced atherosclerosis. The study is limited by convenient sampling and lack of external validation of the model.