Evening workouts associated with lower mortality in type 2 diabetes

Patients with type 2 diabetes and obesity who worked out in the evening had greater reductions in risk for mortality and cardiovascular and microvascular disease than those who exercised in the morning or afternoon, a retrospective study found.

Evening exercise was associated with the lowest incidence of mortality and cardiovascular morbidity compared to working out at other times of day, a study found.

To assess the association between timing of moderate to vigorous aerobic physical activity and risk of cardiovascular disease, microvascular disease, and all-cause mortality in adults with obesity and/or type 2 diabetes, researchers used data from a large prospective cohort study containing accelerometer-based physical activity data. Aerobic activity was defined as a bout lasting three or more continuous minutes. Between 2013 and 2015, participants wore an accelerometer on their dominant wrist 24 hours a day for seven days. Participants were categorized into morning, afternoon, or evening groups based on when they did most of their aerobic activity.

The core sample included 29,836 adults with obesity, with a mean age of 62.2 years. Over a mean follow-up period of 7.9 years, 1,425 deaths, 3,980 cardiovascular events, and 2,162 microvascular disease events occurred. Results were published by Diabetes Care on April 10.

Compared with patients who engaged in less than one bout of exercise per day, those who did evening activity had the lowest risk of mortality (hazard ratio [HR], 0.39; 95% CI, 0.27 to 0.55). Afternoon (HR, 0.60; 95% CI, 0.51 to 0.71) and morning (HR, 0.67; 95% CI, 0.56 to 0.79) activity had significant but weaker associations. Similar patterns were observed for cardiovascular and microvascular risk. Evening activity was associated with HRs of 0.64 (95% CI, 0.54 to 0.75) and 0.76 (95% CI, 0.63 to 0.92), respectively.

Findings were similar but even stronger in the subgroup of patients with type 2 diabetes (n=2,995). Evening exercise was again associated with the biggest drop in mortality risk (HR, 0.24; 95% CI, 0.08 to 0.76); afternoon showed a smaller association (HR, 0.44; 95% CI, 0.28 to 0.72), while the difference wasn't significant with morning activity (HR, 0.86; 95% CI, 0.57 to 1.29). For cardiovascular risk, the HRs were 0.54 (95% CI, 0.34 to 0.86), 0.73 (95% CI, 0.56 to 0.94), and 0.85 (95% CI, 0.69 to 1.06), respectively. A significant effect on microvascular disease was only seen with evening exercise (HR, 0.52; 95% CI, 0.32 to 0.86).

"These findings demonstrate a compelling connection between MVPA [moderate to vigorous physical activity] timing and a lower risk of morbidity and mortality in adults with obesity," the study authors wrote. "…These findings are robust and extend to the subset of participants with [type 2 diabetes], in whom evening MVPA exhibited even more pronounced associations with mortality and cardiovascular morbidity."

They noted that their findings may be related to the concept of the dawn phenomenon, in which patients with diabetes have relatively better insulin sensitivity and glycemia in the evening, which worsens overnight. "Therefore, engaging in MVPA later in the afternoon or evening, when postprandial glycemia is highest and hepatic insulin sensitivity begins to decline, may elicit the greatest metabolic benefits by directly influencing these pathways and leading to lower morning fasting glucose levels," the study authors wrote.