Abstract T P147: Vitamin D Deficiency is Associated With Stroke in ethnic Chinese but Not South Asians in a Case-Control Study

Abstract

Vitamin D deficiency is associated with risk of stroke and coronary artery disease in whites but not in blacks. There are no such data comparing Asian ethnicities with differing skin pigmentation. Compared to ethnic Chinese, ethnic South Asians are comparatively of darker pigmentation and are have lower vitamin D levels. We aimed to determine any ethnic interaction between vitamin D and ischemic stroke in a case-control study of ethnic Chinese and South Asians. We recruited 271 ischemic stroke patients of Chinese (87%) and South Asian (13%) ethnicity with blood samples taken within 2 weeks of onset to reflect pre-stroke levels. They were matched for age, gender and ethnicity to 271 stroke-free controls from a population-based study. Serum 25 hydroxyvitamin D [25(OH)D] levels were measured using competitive electroluminescence immunoassay in an accredited laboratory, blinded to clinical data. Among the cases and controls, the ethnic distribution was 87% Chinese and 13% South Asian. Mean 25(OH)D levels were lower in South Asians than Chinese among stroke cases (19.1 ± 8.4 vs 24.6 ± 9.3μg/L; p=0.001), and among controls (16.7 ± 6.6 vs 29.3 ± 9.7μg/L; p<0.001). Among Chinese, 25(OH)D levels were lower in stroke cases than controls (p<0.001), however this was not observed among South Asians (p=0.188). There was an interaction between ethnicity with the association of 25(OH)D levels and stroke (p <0.001), which remained even after adjusting for covariates of diabetes, hypertension, hyperlipidemia, previous myocardial infarction and smoking status as well as calcium, phosphate, and PTH levels (p=0.003). The relationship between vitamin D and stroke risk differed between Chinese and South Asians, consistent with studies of ethnic groups with differing skin pigmentation. This adds to evidence of a possible adaptive mechanism towards the consequences of vitamin D deficiency in ethnicities with darker pigmentation. Furthermore, ethnicity should be an important consideration in vitamin D-related epidemiology and treatment studies.