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ExerciseOct 23, 2023

Researchers extol the health benefits that come from promoting improved physical activity levels

Being physically active for just 20 to 25 minutes a day may be enough to offset the heightened risk of death from a highly sedentary lifestyle, according to an article that was published online in the British Journal of Sports Medicine today (25 October).

Lead author Edvard Sagelv, from UiT The Arctic University of Norway in Tromsø, Norway, and colleagues found that higher daily tallies of physical activity are linked to a lower risk – irrespective of the amount of time people spent seated every day.

In developed nations, adults spend an average of 9 to 10 hours sitting every day – mostly during working hours. And a highly sedentary lifestyle is associated with a heightened risk of death, explain the researchers.

Much of the previously published research on the benefits of physical activity to counter prolonged sitting time have relied on aggregated data, which inevitably results in a broad-brush approach, Mr Sagelv and his colleagues suggest.

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Higher daily tallies are linked to lower risks, however long the over-50s spend seated

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Clocking up 22 minutes of 'vigorous' activity a day was crucial 

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 from 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.

Almost 12,000 people aged at least 50 were included in the analysis. They had a minimum of four days of 10 daily hours of activity tracker records, had been monitored for at least two 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.

A total of 5,943 people spent fewer than 10.5 hours sitting down every day; 6,042 clocked up 10.5 or more sedentary hours.Linkage with death registries showed that during an average period of five years, 805 (7 per cent) people died, 357 (6 per cent) 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 per cent heightened risk of death compared with a daily tally of eight hours – but only among those accruing fewer than 22 daily minutes of moderate to vigorous physical activity.

Small amounts of MVPA may be an effective strategy to ameliorate the mortality risk from high sedentary time ... efforts to promote physical activity may have substantial health benefits for individuals [Edvard Sagelv et al]

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 per cent lower risk of death in those spending fewer than 10.5 sedentary hours, and a 35 per cent 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-plus daily hours).

Conclusions

Mr Sagelv and his colleagues acknowledge that their study was observational in nature and cannot establish cause and effect. They could not 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 team concludes: '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.'

Mr Sagelv and his colleagues add: ‘Efforts to promote physical activity may have substantial health benefits for individuals.’

To access the full version of the article – titled Device-measured physical activity, sedentary time, and risk of all-cause mortality: an individual participant data analysis of four prospective cohort studies doi 10.1136/bjsports-2022-106568 – click 

Author: Ian A McMillan
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