Early birds get the burn: Monash study finds early bedtimes associated with more physical activity

(Press-News.org) Going to bed earlier than usual may help to optimise physical activity the following day, Monash University-led research has found.

Published in Proceedings of the National Academy of Sciences (PNAS), the study examined whether sleep duration and sleep timing were associated with the duration of moderate-to-vigorous and overall physical activity the following day.

In the primary study, almost 20,000 participants wore a validated biometric device (WHOOP) for one year, resulting in almost six million nights of data. Objective sleep and physical activity metrics were derived from the wrist-worn device.

The study examined how both typical sleep habits and nightly fluctuations in sleep were linked to next-day physical activity levels.

On average, people who went to bed earlier were more physically active. For example, those with a typical bedtime around 9pm logged about 30 more minutes of moderate-to-vigorous physical activity each day compared to those who regularly stayed up until 1am.

Even compared to those who typically went to bed at 11pm (the average bedtime for the entire sample), the 9pm sleepers recorded nearly 15 additional minutes of daily moderate-to-vigorous physical activity.

Lead author Dr Josh Leota, from Monash University’s School of Psychological Sciences, said the findings suggested individuals with later bedtimes may be at a disadvantage under conventional work schedules.

“Standard 9-to-5 routines can clash with the natural sleep preferences of evening types, leading to social jetlag, poorer sleep quality, and increased daytime sleepiness – which can all reduce motivation and opportunity for physical activity the next day,” Dr Leota said.

Importantly, the study also looked at whether individuals can actively alter this relationship. The researchers found that when people went to sleep earlier than usual but still got their typical amount of sleep, they recorded the highest levels of physical activity the next day.

“These insights carry meaningful implications for public health,” Dr Leota said. “Rather than just promoting sleep and physical activity independently, health campaigns could encourage earlier bedtimes to naturally foster more active lifestyles. A holistic approach that recognises how these two essential behaviours interact may lead to better outcomes for individual and community health.”

An additional validation study involving almost 6000 participants from the All of Us Research Program, using Fitbit data, reinforced these findings, showing the relationships were broadly consistent across diverse populations.

Senior author Dr Elise Facer-Childs, from the Monash University School of Psychological Sciences, said that these findings highlight a powerful relationship between sleep timing and physical activity.

“Sleep and physical activity are both critical to health, but until now we didn't fully grasp how intricately connected they are in everyday life,” Dr Facer-Childs said.

“Our findings are consistent across different populations, and show that if you can get to sleep earlier than usual whilst keeping your sleep duration the same, you may be more likely to increase your physical activity the following day”, says Dr Facer-Childs.

Read the research paper here: DOI 10.1073/pnas.2420846122

The researchers are only available by email. Audio and video assets, for use after the embargo lifts, available here from Monday 30 June.

This research was conducted in collaboration with Brigham and Women’s Hospital, Harvard Medical School, WHOOP Inc., the Swiss Institute of Bioinformatics, the University of Lausanne, and Flinders University.

 

END