Retiring to bed earlier may assist you in achieving fitness aspirations

The adage states, early to bed and early to rise fosters a person’s health, affluence, and sagacity.

Wealth and wisdom may still remain a conundrum, yet sleep specialists at Harvard, Brigham and Women’s Hospital, and Monash University assert there’s compelling proof that turning in earlier than typical and obtaining adequate rest can enhance a vital element of good health: attaining sufficient heart-rate-increasing physical activity.

The research, which took place from 2021 to 2022, revealed that individuals who achieved the highest levels of moderate-to-vigorous physical activity the following day slept earlier than their usual schedule, yet their total sleep duration remained comparable. The most significant contrast in subsequent day activity was noted between individuals who generally averaged 5 hours of sleep per night and those who managed 9 hours. In this instance, the short sleepers gained an additional 41.5 minutes of moderate-to-vigorous physical activity the next day.

“Generally, individuals who went to bed earlier participated in more frequent and extended physical activity daily compared to those who routinely went to bed later,” stated Mark Czeisler, a clinical fellow in medicine at Harvard Medical School, resident physician at Brigham and Women’s Hospital, and co-author of the study.

Czeisler, who completed his undergraduate studies at Harvard College in 2019 and graduated from HMS in May, suggested that those individuals might have been better refreshed and more motivated to exercise, but it could also be that retiring to bed earlier allowed them to awaken sooner, thus providing additional time in their day. Identifying specific causes and impacts, he mentioned, would be a future objective of further research.

U.S. health directives recommend that adults achieve 150 to 300 minutes of moderate-to-vigorous physical activity weekly. Moderate activities include those that induce sweating and elevate heart rate and breathing, such as brisk walking, cycling, or gardening. Vigorous activities make it challenging to converse during them and encompass activities such as running, swimming, and basketball.

“The main takeaway is that sleep and physical activity may be more interconnected than we previously assumed,” remarked Josh Leota, adjunct researcher with the Brigham’s Division of Sleep and Circadian Disorders, research fellow at Monash University in Australia, and the primary author of the paper. “Even minor adjustments in bedtime could be associated with your level of activity the next day. Therefore, instead of perceiving sleep and exercise as competing for hours, we should consider how they can complement each other.”

The study, released in June in the Proceedings of the National Academy of Sciences, leverages advancements in wearable fitness devices, which provided daily sleep and activity information for nearly 20,000 Americans who recorded almost 6 million nights over the span of a year.

Researchers utilized anonymized data from WHOOP Inc., a Boston-based health tracker technology company rooted at Harvard. The results from WHOOP were confirmed by a secondary investigation, All of Us, conducted by the National Institutes of Health, which provided a demographically representative cohort with free Fitbit devices for participation.

Czeisler noted that the All of Us study indicated similar trends between sleep and physical activity, though the magnitude of the effect was reduced. This could be attributed to differences among the study populations, he indicated, with the WHOOP cohort being more inclined to self-select for an interest in fitness and athletic performance.

The research, conducted without external funding, clarifies an area where earlier studies produced mixed results.

Some studies failed to demonstrate any association between sleep patterns and levels of moderate-to-vigorous physical activity. Others, however, do establish a link, albeit suggesting different conclusions. Controlled experimental studies indicated reduced physical activity the following day for those who garnered less sleep than usual, while epidemiological investigations—often carried out via questionnaires among individuals in typical conditions—suggested the opposite.

One advantage of the present study is that acquiring longitudinal data from two substantial samples over several months and up to a year allows for both comparisons between participants and “within participant” analyses of an individual’s tracker data under varying situations.

Additionally, Czeisler mentioned that objective tracker data mitigates potential biases or recall difficulties commonly found in questionnaire-based studies.

Although both sleep and physical activity have been explored previously, Czeisler asserted that the current work is among the largest in participant size and the longest in duration to investigate the relationship between the two in everyday contexts. This is significant, as health practitioners and public health officials often deliver separate guidance about optimal sleep amounts and ideal physical activity levels for wellness, but there lacks public health communication surrounding how one might influence the other.

Busy adults might opt, for instance, to reduce sleep, rising early to engage in workouts. Alternatively, they may decide to stay out late with friends on Friday and Saturday evenings, which may influence weekend exercise routines.

“If one of the conclusions is that individuals are forfeiting sleep for exercise or vice versa, the critical question becomes: what amount of each behavior optimizes health span and lifespan?” Czeisler said. “With only 24 hours in a day, what constitutes the optimal equilibrium?”

Leota mentioned an essential next step is to utilize the findings to design experiments to ascertain causality, aiming at a robust basis for forthcoming public health recommendations.

“We would like to explore whether promoting earlier bedtimes directly leads to increased physical activity the following day, within an experimental framework,” Leota commented. “This would yield strong evidence to update public health messaging aimed at enhancing community physical activity levels.”