Serum 25-hydroxyvitamin D [25(OH)D] is known to be associated with depression. However, the evidence concerning the association between vitamin D status and depressive episodes in population with prediabetes and diabetes remains limited. This study seeks to investigate the potential relationship between vitamin D levels and depression in this population.

This cohort study comprised 55,252 individuals with prediabetes and 17,369 patients with diabetes, who exhibited no signs of depression at baseline. Baseline 25(OH)D concentrations were assessed. Cox proportional hazard models were employed to estimate hazard ratios (HRs) and 95% CIs for depression, with adjustments made for potential confounding variables.

Over a mean follow-up period of 11.7 years, a total of 2,409 depression events were documented in participants with diabetes; and 6,078 depression events were recorded in the prediabetic participants, during a mean follow-up of 12.3 years. Vitamin D sufficiency (≥75 nmol/L) was observed in only 12.5% of individuals with prediabetes and 11.3% of those with diabetes. After multivariate adjustment, an inverse and dose-dependent relationship was identified between serum 25(OH)D concentrations and the risk of depression in prediabetic and diabetic participants (P trend <0.05). Compared with the lowest 25(OH)D level (<25 nmol/L), the highest level (≥75 nmol/L) exhibited a 17% reduction in the risk of depressive events (HR 0.83; 95% CI 0.75−0.93) among individuals with prediabetes and a 25% reduction (HR 0.75; 95% CI 0.61−0.90) among those with diabetes。

The findings of this study highlight the critical importance of prioritizing serum 25(OH)D levels in the management of depression in patients with diabetes and prediabetes.