Effect of intra-trial mean 25(OH)D level on diabetes risk, by race and weight: an ancillary analysis in the D2d randomized study cohort.
Academic Article
Overview
abstract
BACKGROUND: Higher serum 25-hydroxyvitamin D [25(OH)D] is associated with lower type 2 diabetes risk. 25(OH)D varies due to skin pigmentation and weight. OBJECTIVE: To determine if people of color and those with overweight/obesity (who have higher diabetes risk) have different associations between 25(OH)D and diabetes risk than individuals who are White or normal weight. METHODS: The D2d study is a randomized clinical trial in people with prediabetes that studied effects of daily vitamin D3 4000 IU vs placebo on diabetes risk (median follow-up 2.5 years). Among D2d participants, we compared baseline and intra-trial mean 25(OH)D levels, defined as mean of all available annual 25(OH)D values, among groups defined by self-reported race and body mass index (BMI). We used Cox proportional hazards models to assess associations between intra-trial mean 25(OH)D and diabetes risk by race- and BMI-based groups. RESULTS: Asian (n=130), Black (n=616), and White (n=1616) participants were included. Both baseline and intra-trial mean 25(OH)D levels differed significantly by race groups (both P <0.001) and were lower in Asian and Black vs. White participants; and in those with higher vs. lower BMI adjusted for race (both P <0.001). Compared to those with lower levels, Black and White participants with intra-trial mean 25(OH)D ≥40 ng/mL had significantly reduced diabetes risk [HR (95%CI)]: Black: 0.51 (0.29, 0.92); White: 0.42 (0.30, 0.60); and with a similar reduction in diabetes risk among Asian participants: 0.39 (0.14, 1.11). Compared to those with lower levels, participants with baseline BMI <40 kg/m2 who achieved intra-trial mean 25(OH)D levels ≥40 ng/mL had a significantly reduced diabetes risk. There were no significant interaction effects by race or BMI. CONCLUSIONS: Among people with prediabetes, particularly for Black and White race groups and those with BMI <40 kg/m2, the optimal 25(OH)D level may be ≥ 40 ng/mL to optimize diabetes prevention efforts. TRIAL IDENTIFIER: D2d ClinicalTrials.gov number, NCT01942694 https://clinicaltrials.gov/ct2/show/NCT01942694.
