Recent research published in the British Journal of Sports Medicine suggests that incorporating a mere 20-25 minutes of physical activity into one’s daily routine could significantly counterbalance the increased mortality risk associated with a highly sedentary lifestyle. The study underscores that while more substantial amounts of daily physical activity are linked to further reductions in death risk, these benefits are evident regardless of the time individuals spend seated each day.
In developed countries, it’s common for adults to spend between 9 and 10 hours a day seated, predominantly during work hours. Such extensive periods of sedentariness are linked to a greater risk of death, the researchers point out. Prior studies exploring the protective effects of physical activity against the dangers of prolonged sitting often relied on aggregated data, leading to a generalized approach to findings. In contrast, this study aimed for a more nuanced understanding by analyzing individual data from people equipped with activity trackers. This approach helped to assess how physical activity might influence the relationship between sedentary time and mortality risk, and vice versa, and to determine the specific amounts of physical activity and sedentary behaviour affecting this risk.
The analysis included data collected from 2003 to 2019 through four distinct cohorts: the Norwegian Tromsø Study of 2015-16, the Swedish Healthy Ageing Initiative from 2012 to 2019, the Norwegian National Physical Activity Survey of 2008-09, and the US National Health and Nutrition Examination Survey from 2003 to 2006. Nearly 12,000 individuals aged 50 or above were part of the study, each having at least four days of activity tracker data representing ten daily hours over a minimum two-year monitoring period. These participants also provided information on several factors that could influence outcomes, including their gender, education level, body metrics, smoking and drinking habits, and history of cardiovascular disease, cancer, or diabetes.
The study’s findings revealed that of the participants, 5943 spent less than 10.5 hours per day sitting, while 6042 exceeded this amount of sedentary time. Over an average follow-up period of five years, 805 individuals passed away, with a lower proportion of deaths among those who sat for less than 10.5 hours a day. Significantly, spending more than 12 hours a day in sedentary activities was linked to a 38% increased risk of death compared to sitting for 8 hours a day. Still, this risk was only evident among participants with less than 22 minutes of daily moderate to vigorous physical activity (MVPA). Conversely, exceeding 22 minutes of MVPA daily was associated with a lower death risk.
Furthermore, the study illustrated that while higher levels of MVPA were consistently associated with a reduced death risk regardless of sedentary time, the specific relationship between sitting time and mortality largely depended on moderate to vigorous activity volume. For instance, an additional 10 minutes of MVPA per day corresponded to a 15% lower death risk among those sitting less than 10.5 hours a day and a 35% reduction for those sitting more. Light physical activity only benefited those who were highly passive (spending over 12 hours a day sitting).
It’s important to note that the study is observational and cannot prove causation. The researchers also acknowledged limitations, such as the inability to update physical activity and sedentary time measurements over time and the exclusion of potential influencing factors like diet, mobility issues, and overall health status. Additionally, activity trackers may only accurately classify some types of activities and their intensity levels.
Despite these limitations, the research offers a compelling argument: even small quantities of moderate to vigorous physical activity can significantly mitigate the mortality risks associated with high sedentary time. Accumulating more than 22 minutes of such activity daily can eliminate the heightened risk of extended sitting periods. Therefore, promoting physical activity is a crucial strategy with potentially extensive health benefits for the public.
More information: Edvard H Sagelv et al, Device-measured physical activity, sedentary time, and risk of all-cause mortality: an individual participant data analysis of four prospective cohort studies, British Journal of Sports Medicine. DOI: 10.1136/bjsports-2022-106568
Journal information: British Journal of Sports Medicine Provided by BMJ
