25 Minutes of Physical Activity May Offset Risk of Death From Prolonged Sitting
Physical activity may offset some of the negative effects that come with a sedentary lifestyle
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Just 20–25 minutes of moderate to vigorous physical activity each day may be enough to combat a highly sedentary lifestyle's increased risk of death, suggests a new study in the British Journal of Sports Medicine.
The dangers of a sedentary lifestyle
It is well known that a highly sedentary lifestyle can lead to an increased risk of death. This is particularly pressing in developed nations, where people are estimated to sit down for 9–10 hours each day – largely during working hours.
Previous research has investigated claims that physical activity may be able to offset some of the negative effects that come with a sedentary lifestyle. However, this kind of research can take a “broad brush approach” in relying on aggregated data.
In the current study, researchers have attempted to overcome these issues by analyzing pooled data from individual participants fitted with activity trackers across four different studies. This could help us to understand how physical activity may alter the relationship between sedentary time and risk of death, while potentially informing the amount of physical activity and sitting time required to influence this risk.
Physical activity may offset risks
In their study, the researchers analyzed data from almost 12,000 individuals, collected from 2003–2019 as part of four studies – 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.
Participants were aged 50 years and over, had a minimum of 4 days of activity tracker records (with 10 hours tracked per day) and had been monitored for at least 2 years. Additionally, their records included information on other variables that could influence their results, such as sex, weight, height, smoking history, etc.
Of the almost 12,000 participants, 5,943 people sat down for fewer than 10.5 hours per day, while 6,042 sat for over 10.5 hours.
In total, 805 people (7% of the cohort) passed away over an average period of 5 years; 357 of these sat for 10.5 hours per day, while 448 sat for over 10.5 hours.
Being sedentary for 12 hours per day was associated with a 38% higher risk of death compared to 8 sedentary hours – but, according to the activity tracker data, this was only true for those who achieved fewer than 22 minutes of moderate to vigorous daily physical activity.
On the other hand, achieving over 22 minutes of this level of physical activity per day 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 of physical activity per day was associated with a 15% lower risk of death in those achieving less than 10.5 sedentary hours, and a 35% lower risk among those spending more than 10.5 sedentary hours.
Though moderate to vigorous physical activity had the most effect, those classified as highly sedentary (over 12 daily sedentary hours) could still benefit from light intensity physical activity in reducing the risk of death.
“Substantial health benefits”
The researchers acknowledge some limitations to the study, noting that they couldn’t repeat measures of physical activity and sedentary hours, therefore preventing any changes in either over time. Importantly, they also note that as this was an observational study, it cannot establish cause and effect.
Additionally, though some potentially influential factors such as smoking history and alcohol intake were considered, other factors such as diet, mobility issues and general health weren’t accounted for. Moreover, activity trackers may not correctly classify the intensity of different activities, such as cycling, resistance training or gardening.
“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,” the researchers write in the study. “Efforts to promote physical activity may have substantial health benefits for individuals.”
Reference: Sagelv EH, Hopstock LA, Morseth B, et al. Device-measured physical activity, sedentary time, and risk of all-cause mortality: an individual participant data analysis of four prospective cohort studies. Br J Sports Med. 2023. doi: 10.1136/bjsports-2022-106568
This article is a rework of a press release issued by the British Medical Journal. Material has been edited for length and content.