Association between serum 25-hydroxyvitamin D and visceral fat area in adults with type 2 diabetes: A cross-sectional study.

ObjectiveTo examine the association between serum 25-hydroxyvitamin D and visceral fat area in adults with type 2 diabetes and assess the exposure-response pattern.MethodsThis retrospective cross-sectional study included 1271 adults with type 2 diabetes. Serum 25-hydroxyvitamin D was analyzed as a continuous variable and by quartiles. Multivariable linear regression models were sequentially adjusted for demographic, lifestyle, and metabolic factors, with body mass index added separately in the fully adjusted model. A generalized additive model was used to assess the exposure-response relationship. Prespecified subgroup analyses were also performed.ResultsVisceral fat area differed across quartiles of serum 25-hydroxyvitamin D, with a lower median value in Q4 than in Q1 (87.0 vs. 96.0 cm2; p = 0.002). Higher serum 25-hydroxyvitamin D was associated with lower visceral fat area in the multivariable model without body mass index (β = -0.77, 95% confidence interval: -1.13 to -0.41; p < 0.0001) and in the body mass index-adjusted model (β = -0.53, 95% confidence interval: -0.80 to -0.27; p < 0.0001). In quartile analyses, participants in Q4 had lower visceral fat area than those in Q1 in the body mass index-adjusted model (β = -10.04, 95% confidence interval: -16.19 to -3.89; p = 0.0015), whereas the associations for Q2 and Q3 were not statistically significant; nevertheless, a significant trend was observed across quartiles (p for trend = 0.0005). The generalized additive model suggested an approximately linear inverse association between serum 25-hydroxyvitamin D and visceral fat area.ConclusionsIn adults with type 2 diabetes, higher serum 25-hydroxyvitamin D levels were associated with lower HDS-2000-estimated visceral fat area, although the association was attenuated after adjustment for body mass index. This cross-sectional association should not be interpreted as independent of overall adiposity or unmeasured lifestyle, comorbidity, and treatment-related factors. Longitudinal studies are needed to clarify temporality.