Higher Daily Counts Are Associated With a Reduced Risk Regardless of Sitting Time in Those Over 50
Engaging in just 20-25 minutes of daily physical activity could counteract the increased mortality risk associated with a predominantly sedentary lifestyle, according to a study published in the British Journal of Sports Medicine.
However, the study also indicates that higher daily tallies of physical activity are linked to lower risk, irrespective of the amount of time spent seated every day.
In developed nations, adults spend an average of 9 to 10 hours every day sitting down—mostly during working hours. And a highly sedentary lifestyle is associated with a heightened risk of death, explain the researchers.
Research Methodology and Data Collection
Much of the previously published research on the benefits of physical activity to counter prolonged sitting time has relied on aggregated data, which inevitably results in a broad brush approach, they suggest.
To try and overcome this, the researchers pooled individual participant data from four groups of people fitted with activity trackers to find out whether physical activity might modify the association between sedentary time and death, and vice versa, and what amount of physical activity and sitting time might influence risk.
They included individual participant data collected between 2003 and 2019 from the Norwegian Tromsø Study 2015–16; the Swedish Healthy Ageing Initiative (HAI) 2012–19; the Norwegian National Physical Activity Survey (NNPAS) 2008– 09; and the US National Health and Nutrition Examination Survey (NHANES) 2003–06.
Just short of 12,000 people aged at least 50 were included in the analysis. They had a minimum of 4 days of 10 daily hours of activity tracker records, had been monitored for at least 2 years, and had provided details of potentially influential factors: their sex, educational level, weight, height, smoking history, alcohol intake, and whether they had current and/or previous cardiovascular disease, cancer and/or diabetes.
Key Findings
In all, 5943 people spent fewer than 10.5 hours sitting down every day; 6042 clocked up 10.5 or more sedentary hours.
Linkage with death registries showed that during an average period of 5 years, 805 (7%) people died, 357 (6%) of whom spent under 10.5 hours sitting down every day, and 448 of whom clocked up 10.5 hours or more.
The analysis of the activity tracker data showed that being sedentary for more than 12 hours a day was associated with a 38% heightened risk of death compared with a daily tally of 8 hours—but only among those totting up fewer than 22 daily minutes of moderate to vigorous physical activity.
More than 22 daily minutes of moderate to vigorous physical activity was associated with a lower risk of death.
While a higher amount of moderate to vigorous physical activity was associated with a lower risk of death, irrespective of the amount of sedentary time, the association between sedentary time and death was largely influenced by the amount of moderate to vigorous physical activity.
For example, an extra 10 minutes a day was associated with a 15% lower risk of death in those spending fewer than 10.5 sedentary hours, and a 35% lower risk among those spending more than 10.5 sedentary hours, every day.
Light-intensity physical activity was only associated with a lower risk of death among highly sedentary people (12+ daily hours).
Limitations and Conclusions
This is an observational study, and as such, can’t establish cause and effect. The researchers acknowledge that they weren’t able to repeat measures of physical activity and sedentary hours, so precluding any changes in either over time.
Potentially influential factors, such as diet, mobility issues, and general health weren’t accounted for either. And activity trackers may not correctly classify all activity types and their corresponding intensity—cycling, resistance exercises, and gardening, for example.
Nevertheless, the researchers conclude: “Small amounts of MVPA [moderate to vigorous physical activity] may be an effective strategy to ameliorate the mortality risk from high sedentary time, where accumulating more than 22 mins of MVPA eliminates the risk of high sedentary time.
“Efforts to promote physical activity may have substantial health benefits for individuals.”
Reference: “Device-measured physical activity, sedentary time, and risk of all-cause mortality: an individual participant data analysis of four prospective cohort studies” by Edvard H Sagelv, Laila Arnesdatter Hopstock, Bente Morseth, Bjørge H Hansen, Jostein Steene-Johannessen, Jonas Johansson, Anna Nordström, Pedro F Saint-Maurice, Ola Løvsletten, Tom Wilsgaard, Ulf Ekelund and Jakob Tarp, 24 October 2023, British Journal of Sports Medicine.
DOI: 10.1136/bjsports-2022-106568
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