Association Between Serum 25(OH)D and Cardiovascular Morbidity and Mortality in People with Type 2 Diabetes: a Community-based Cohort Study

Aim: We aimed to explore the association between vitamin D and cardiovascular morbidity and mortality in people with Type 2 diabetes recruited from a community-based study because there is limited and inconsistent research of this group.

Methods: A prospective community-based cohort study among people aged 55-66 years with Type 2 diabetes as part of The Cardiovascular Risk in Type 2 Diabetes - A Prospective Study in Primary Care (CARDIPP). We analysed serum 25-hydroxyvitamin D [25(OH)D ] at baseline. Cox regression analyses were used to calculate hazard ratios (HR) for the first myocardial infarction, stroke or cardiovascular mortality according to 25(OH)D .

Results: We examined 698 people with a mean follow-up of 7.3 years. Serum 25(OH)D was inversely associated with the risk of cardiovascular morbidity and mortality: HR 0.98 [95% confidence interval (CI) 0.96 to 0.99, P = 0.001]. Compared with the fourth quartile (Q4) [25(OH)D > 61.8 nmol/l], HR (with 95% CI) was 3.46 (1.60 to 7.47) in Q1 [25(OH)D < 35.5 nmol/l] (P = 0.002); 2.26 (1.01 to 5.06) in Q2 [25(OH)D 35.5-47.5 nmol/l] (P = 0.047); and 1.62 (0.70 to 3.76) in Q3 [25(OH)D 47.5-61.8 nmol/l] (P = 0.26) when adjusting for age, sex and season. The results remained significant after adjusting also for cardiovascular risk factors, physiological variables including parathyroid hormone and previous cardiovascular disease (P = 0.027).

Conclusions: Low 25(OH)D is associated with an increased risk of cardiovascular morbidity and mortality in people with Type 2 diabetes independent of parathyroid hormone. Vitamin D could be considered as a prognostic factor. Future studies are needed to explore whether vitamin D deficiency is a modifiable risk factor in Type 2 diabetes.