Seasonal variations on endothelium-dependent flow-mediated vasodilation in adults with type 2 diabetes and nondiabetic adults with hypertension and/or dyslipidaemia who perform regular exercise.

Introduction:Endothelium-dependent flow-mediated dilation (FMD) of the brachial artery often changes seasonally. We aimed to examine the association between the seasonal variation on FMD and regular exercise in adults with type 2 diabetes (T2D) and nondiabetic adults with hypertension and/or dyslipidaemia (non-T2D). Methods:This retrospective study included 14 T2D and 17 non-T2D adults, who started to perform moderate-intensity aerobic exercise for 30-40 min/d at a hospital gym in 2006-2010 and maintained exercise performance at least 2 d/wk until the end of the observation period. We observed and analysed the data for 5 years (from March 2011 to February 2016). FMD, cardio-ankle vascular index (CAVI) and metabolic outcomes were compared among seasons in the T2D and non-T2D groups. Results:The FMD values were lower in winter than in other seasons in both groups (all P < .01). The annual range of FMD was larger by 31% in the T2D group than in the non-T2D group (P < .05). The systolic blood pressure (BP) values were higher in winter than in other seasons in both groups (all P < .01), and the diastolic BP values were higher in winter than in summer in both groups (T2D: P < .05; non-T2D: P < .01). CAVI and other outcomes did not change seasonally. Conclusions:Flow-mediated vasodilation showed seasonal variation in T2D adults, even if they performed exercise regularly for a long period of time. Additionally, we found that the annual range of FMD might increase with the presence of T2D.