Effects of morning versus evening exercise on vascular function in older adults with type 2 diabetes: a randomised controlled trial

Background Cardiovascular disease is a common complication of type 2 diabetes mellitus (T2DM), with increased risk closely associated with vascular dysfunction. Exercise is an effective strategy for improving vascular health, but whether exercise timing influences long-term vascular adaptations in patients with T2DM remains unclear. In this study, we investigated the effects of morning versus evening exercise on vascular function in older adults with T2DM. Methods Sixty-six older adults with T2DM were randomised to morning exercise, evening exercise, or control (n = 22 each). The exercise groups received 12 weeks of online moderate-intensity aerobic and resistance exercises, three times per week. The morning group exercised from 9:00 to 10:10, and the evening group from 19:00 to 20:10. The control group maintained their usual lifestyle and attended weekly health education sessions without structured exercise. Blood pressure, brachial-ankle pulse wave velocity (baPWV), flow-mediated vasodilation (FMD) and plasma nitric oxide (NO) levels were assessed at baseline and post-intervention. Outcomes were analysed using two-way repeated-measures analysis of variance, with exploratory analyses directly comparing the two exercise groups. Results Fifty-eight participants were included in the final analysis (morning, n = 20; evening, n = 19; control, n = 19). Significant group × time interactions were observed for FMD, baPWV, systolic blood pressure (SBP), mean arterial pressure (MAP), and plasma NO (all p < 0.05). Both exercise groups increased FMD and reduced SBP, MAP, and baPWV from baseline (all p < 0.05). Plasma NO increased significantly following the evening exercise (p = 0.003), whereas no significant changes were observed following the morning exercise (p = 0.722). At post-intervention, the evening group exhibited lower MAP (p = 0.012) and higher FMD (p = 0.019) and NO levels (p = 0.012) than controls. Exploratory analyses showed a greater baPWV reduction with evening exercise (group × time interaction, p = 0.034). The increase in plasma NO was numerically greater with evening exercise, although the interaction was not statistically significant (p = 0.051). Conclusions Exercise timing may influence vascular adaptations in older adults with T2DM, with evening exercise potentially offering additional benefits, particularly for arterial stiffness. Clinical trial registration https://www.chictr.org.cn/showproj.html?proj=200163 , identifier ChiCTR2300073737.