Effect of waist circumference on the association between serum 25-hydroxyvitamin D and serum lipids: results from the National Health and Nutrition Examination Survey 2001-2006

Objective: To examine the interaction between waist circumference (WC) and serum 25-hydroxyvitamin D (25(OH) D) level in their associations with serum lipids. Design: Cross-sectional study. The associations of serum 25(OH) D with total cholesterol, HDL cholesterol (HDL-C), LDL cholesterol (LDL-C), LDL-C: HDL-C and TAG were examined using multiple linear regression. Effect modification by WC was assessed through cross-product interaction terms between 25(OH) D and WC categories (abdominal overweight, 80-<88 cm in females/94-<102 cm in males; abdominal obesity, >= 88 cm in females/>= 102 cm in males). Setting: The US National Health and Nutrition Examination Survey waves 2001-2006. Subjects: Non-pregnant fasting participants (n 4342) aged >= 20 years. Results: Lower 25(OH) D levels were significantly associated with lower HDL-C levels as well as with higher LDL-C: HDL-C and TAG levels in abdominally obese participants, but not in abdominally overweight or normal-waist participants. In contrast, lower 25(OH) D levels were associated with lower levels of total cholesterol and LDL-C in abdominally overweight and normal-waist participants only, but this association was only partly significant. However, a significant difference in the association between 25(OH) D and the lipids according to WC category was found only for LDL-C: HDL-C (P for interaction=0.02). Conclusions: Our results from this large, cross-sectional sample suggest that the association between lower 25(OH) D levels and an unfavourable lipid profile is stronger in individuals with abdominal obesity than in those with abdominal overweight or a normal WC.