Is Nighttime the Best Time for Exercise?

TOPLINE:

Moderate to vigorous aerobic physical activity performed in the evening is associated with the lowest risk for mortality, cardiovascular disease (CVD), and microvascular disease (MVD) in adults with obesity, including those with type 2 diabetes (T2D).

METHODOLOGY:

• Bouts of moderate to vigorous aerobic physical activity are widely recognized to improve cardiometabolic risk factors, but whether morning, afternoon, or evening timing may lead to greater improvements is unclear.
• Researchers analyzed UK Biobank data of 29,836 participants with obesity (body mass index, › 30; mean age, 62.2 years; 53.2% women), including 2995 also diagnosed with T2D, all enrolled in 2006-2010.
• Aerobic activity was defined as bouts lasting ≥ 3 minutes, and the intensity of activity was classified as light, moderate, or vigorous using accelerometer data collected from participants.
• Participants were stratified into the morning (6 AM to < 12 PM), afternoon (12 PM to < 6 PM), and evening (6 PM to < 12 AM) groups based on when > 50% of their total moderate to vigorous activity occurred, and those with no aerobic bouts were considered the reference group.
• The association between the timing of aerobic physical activity and risk for all-cause mortality, CVD (defined as circulatory, such as hypertension), and MVD (neuropathy, nephropathy, or retinopathy) was evaluated over a median follow-up of 7.9 years.

TAKEAWAY:

• Mortality risk was lowest in the evening moderate to vigorous physical activity group (hazard ratio [HR], 0.39; 95% CI, 0.27-0.55) and even lower in the T2D subgroup (HR, 0.24; 95% CI, 0.08-0.76) than in the reference group.
• Mortality risk was lower in the afternoon (HR, 0.60; 95% CI, 0.51-0.71) and morning (HR, 0.67; 95% CI, 0.56-0.79) activity groups than in the reference group, but this association was weaker than that observed in the evening activity group.
• The evening moderate to vigorous activity group had a lower risk for CVD (HR, 0.64; 95% CI, 0.54-0.75) and MVD (HR, 0.76; 95% CI, 0.63-0.92) than the reference group.
• Among participants with obesity and T2D, moderate to vigorous physical activity in the evening was associated with a lower risk for mortality, CVD, and MVD.

IN PRACTICE:

The authors wrote, "The results of this study emphasize that beyond the total volume of MVPA [moderate to vigorous physical activity], its timing, particularly in the evening, was consistently associated with the lowest risk of mortality relative to other timing windows."

SOURCE:

The study, led by Angelo Sabag, PhD, Charles Perkins Centre, The University of Sydney, Sydney, was published online in Diabetes Care.

LIMITATIONS:

Because this was an observational study, the possibility of reverse causation from prodromal disease and unaccounted confounding factors could not have been ruled out. There was a lag of a median of 5.5 years between the UK Biobank baseline, when covariate measurements were taken, and the accelerometry study. Moreover, the response rate of the UK Biobank was low.

DISCLOSURES:

The study was funded by an Australian National Health and Medical Research Council Investigator Grant and the National Heart Foundation of Australia Postdoctoral Fellowship. The authors reported no conflicts of interest.