Run early, but not too early, for your heart

Good news for morning exercisers! A new analysis of the UK biobank study shows that morning physical activity is associated with lower cardiovascular risk than midday and evening exercise (1). The study, which included 86,657 adults over 40 years with a mean age of 61.6 years and 58% women, aimed to explore the risk of cardiovascular disease, defined as coronary artery disease or cerebrovascular disease, across distinct clusters of patients based on their timing of physical activity, which was assessed using data from wearable accelerometers. During the study, 3707 cardiovascular events were recorded during a follow-up time of six years.

The investigators created clusters based on a data-driven K-means clustering analysis that identified four distinct physical activity clusters: average pattern of the total UK-biobank, early-morning peak, late-morning peak, and evening peak. According to the study, after adjusting for sex and age, morning (08:00-11:00 a.m.), and specifically late-morning physical activity was associated with reduced risk for coronary artery disease (HR 0.84, 95%CI 0.77,0.92) and stroke (HR 0.79, 95%CI 0.64,0.97).

A stratified data analysis revealed that the observed association between the timing of physical activity and cardiovascular risk was significant among women only but not among men (p-for-interaction for sex criteria<0.001). Also, despite lower incident cases among participants in the more active group compared to the less active participants (1396 cases vs. 2311 cases), the beneficial association between morning physical activity and cardiovascular risk was not impacted by the level of physical activity (p>0.05).

The results of this study show, once again, that not all lifestyle habits carry the same benefits and provide novel insights on the possible beneficial effects of morning physical activity, especially in the late morning and mostly among women. This study also suggests that the current approach to physical activity aiming to target “minutes per week” may not be the only relevant recommendation to lower cardiovascular risk and that chrono-activity (i.e., time-dependent physical activity) may be an independent factor affecting cardiovascular risk reduction.