Seasonal variation in estimated cardiovascular risk in patients with type 2 diabetes

Background and aims: Seasonal variations in several risk factors for cardiovascular events (CVD) were described. Here, we evaluate the impact of seasonal variations in blood pressure (BP), lipid profile and glycemic control on estimated CVD risk in patients with type 2 diabetes (T2D). Methods and results: Retrospective monocentric study of patients with T2D who were visited at least once in the winter period and once in the summer period, less than 8 months apart, for which data related to systolic (S) BP, diastolic (D) BP, body mass index, glycosylated hemoglobin (HbA1c), total cholesterol, HDL cholesterol and smoking habit were available on both occasions. The 10-year CVD risk was calculated using the UKPDS risk engine and the ASCVD risk estimator. As many as 411 patients were included in the study. Significant within-patient differences between summer and winter were found for the absolute risk of events assessed with both calculators (Δs-w UKPDS-CHD: −1.33%, Δs-w UKPDS-Stroke: −0.84%, Δs-w ASCVD: −2.21%). The seasonal change in SBP was the main responsible for the change in risk estimated with both the UKPDS-Stroke (r2 = 0.43) and the ASCVD (r2 = 0.50) scores, while the change in total cholesterol was the main determinant of the change in risk for the UKPDS-CHD (r2 = 0.34). A significant correlation was identified between changes in temperature and changes in SBP (ρ = 0.130, p = 0.008), but not in other risk factors. Conclusions: Seasonal variations in the classic CVD risk factors influence the risk estimated using validated calculators.