⚖️ Physical activity or sleep: which is more important?

In the whirlwind of daily priorities, sleep is often relegated to the background, traded for an extra hour of work or a moment of leisure. However, many studies suggest that this trade-off may be to our disadvantage. A recent large-scale analysis reveals an asymmetric and surprising link between our nightly rest and our daytime activity, putting the most common health advice into perspective.

The quest for a balanced lifestyle, centered around sufficient sleep and regular physical activity, seems to be an unattainable ideal for the vast majority of us.

The observation of a widespread double deficit

A research team compiled and examined a phenomenal amount of anonymized data, collected over several years from more than 70,000 people worldwide. This information, from sleep sensors and activity trackers, provides a faithful snapshot of lifestyle habits, far from the sometimes approximate declarations of questionnaires. The resulting panorama is clear: reconciling sleep and movement goals is a rare feat.

Indeed, less than 13% of the individuals monitored simultaneously manage to sleep between 7 and 9 hours and take at least 8,000 steps daily. Conversely, a worrying proportion, nearly one in six, combines short sleep, less than 7 hours, and a sedentary activity level, below 5,000 steps per day. This configuration is regularly associated in the scientific literature with increased risks for physical and mental health.

The meticulous analysis of these millions of days allows going beyond the simple statistical observation. It reveals precise temporal dynamics, showing how nights influence the following days, and vice versa. The researchers were able to model these interactions, highlighting a directional relationship stronger than anticipated. This observation leads to reconsidering the hierarchy of actions to take to improve one's overall lifestyle.

The primacy of sleep over activity

The most striking result of this work, published in Communications Medicine, lies in the asymmetry of the influence between sleep and activity. The data demonstrate that a good quality night, characterized by adequate duration and few awakenings, predisposes to a more active day. Conversely, accumulating steps in a day does not significantly improve the quality or duration of the following sleep. Rest thus appears as the main lever.

Notably, the relationship is not linear. Nights of medium duration, around 6 to 7 hours, are correlated with a greater number of steps the next day, more than for very long nights. The authors emphasize that this finding does not mean that one should reduce their rest time, but that one should aim for efficient sleep. Individuals whose sleep is fragmented or not restorative, regardless of its duration, show overall lower and less regular physical activity.

This discovery offers a pragmatic perspective for people with busy schedules. According to the authors, starting by stabilizing and improving one's sleep could be the most efficient strategy to regain energy and motivation, and thus initiate a virtuous circle. Simple adjustments to the environment and nighttime habits could therefore have an indirect, but substantial, impact on the overall level of physical activity, without requiring additional willpower effort.