How 22 minutes of exercise a day could reduce the health risks from sitting too long

Matthew Ahmadi and Emmanuel Stamatakis for The Conversation

Sydeny: People in developed countries spend an average of nine to ten hours a day sitting. Whether it’s spending time in front of a computer, stuck in traffic, or unwinding in front of the TV, our lives have become increasingly sedentary.

This is concerning because prolonged time spent sitting is linked to a number of health issues including obesity, heart disease, and certain types of cancers. These health issues can contribute to earlier death.

But a new study suggests that for people over 50, getting just 22 minutes of exercise a day can lower the increased risk of premature death from a highly sedentary lifestyle.

What the researchers did

The team combined data from two studies from Norway, one from Sweden and one from the United States. The studies included about 12,000 people aged 50 or older who wore wearable devices to track how active and sedentary they were during their daily routines.

Participants were followed up for at least two years (the median was 5.2 years) during the study period, which spanned 2003-2020.

Analyses took several lifestyle and health factors into account, such as education, alcohol intake, smoking status, and previous history of heart disease, cancer and diabetes. All this data was linked to national death registries.

A 22 minute threshold

A total of 805 participants died during follow up. The researchers found people who were sedentary for more than 12 hours a day had the highest risk of death (a 38 per cent higher risk than people who were sedentary for eight hours).

However, this was only observed in those who did less than 22 minutes of moderate to vigorous physical activity daily. So for people who did more than 22 minutes of exercise, there was no longer a significantly heightened risk – that is, the risk became generally similar to those who were sedentary for eight hours.

Higher daily duration of physical activity was consistently associated with lower risk of death, regardless of total sedentary time. For example, the team reported an additional ten minutes of moderate to vigorous physical activity each day could lower mortality risk by up to 15 per cent for people who were sedentary less than 10.5 hours a day. For those considered highly sedentary (10.5 hours a day or more), an additional ten minutes lowered mortality risk by up to 35 per cent.

The study had some limitations

The team couldn’t assess how changes in physical activity or sedentary time over several months or years may affect risk of death. And the study included only participants aged 50 and above, making results less applicable to younger age groups.

Further, cultural and lifestyle differences between countries may have influenced how data between studies was measured and analysed.

Ultimately, because this study was observational, we can’t draw conclusions on cause and effect with certainty. But the results of this research align with a growing body of evidence exploring the relationship between physical activity, sedentary time, and death.

It’s positive news

Research has previously suggested physical activity may offset health risks associated with high sedentary time.

The good news is, even short bouts of exercise can have these positive effects. In this study, the 22 minutes wasn’t necessarily done all at once. It was a total of the physical activity someone did in a day, and would have included incidental exercise (activity that’s part of a daily routine, such as climbing the stairs).

Several studies using wearable devices have found short bursts of high-intensity everyday activities such as stair climbing or energetic outdoor home maintenance activities such as mowing the lawn or cleaning the windows can lower mortality, heart disease and cancer risk.

Routines such as desk jobs can foster a sedentary lifestyle that may be difficult to shift. But mixing short bursts of activity into our day can make a significant difference towards improving our health and longevity.

Whether it’s a brisk walk during lunch, taking the stairs, or even a short at-home workout, this study is yet another to suggest that every minute counts.

(Matthew Ahmadi is Postdoctoral Research Fellow, Faculty of Medicine and Health, University of Sydney; Emmanuel Stamatakis is Professor of Physical Activity, Lifestyle, and Population Health, University of Sydney)