Sedentary people are advised to do at least one hour of moderate activity a dayBMJ 2016; 354 doi: https://doi.org/10.1136/bmj.i4166 (Published 28 July 2016) Cite this as: BMJ 2016;354:i4166
Doing at least an hour a day of moderate physical activity, such as brisk walking or cycling, seems to eliminate the increased risk of death associated with sitting for more than eight hours a day, a study published in the Lancet shows.1
Researchers used data from 16 studies that had looked at physical activity, sedentary time, and mortality. They analysed the raw study data according to a harmonised protocol that categorised the reported sitting and television viewing time into four standardised groups and the physical activity into quartiles, and they combined the data.
The analysis included data on 1 005 791 people who were followed up for 2-18.1 years, during which time 84 609 (8.4%) died. People who did the least physical activity had a 12-59% higher risk of death during the follow-up period than those who sat for less than four hours and did 60-75 minutes of moderate activity a day. The hazard ratio of the enhanced death rate ranged from 1.12 (95% confidence interval 1.08 to 1.16) in people who did 25-30 minutes’ moderate activity a day and sat for less than four hours, to 1.59 (1.52 to 1.66) in those who did about five minutes’ moderate intensity activity a day and sat for more than eight hours.
Prolonged sitting was also shown to increase the risk of death, but the effect was mitigated in the most active people. People who did 60-75 minutes’ moderate activity a day showed little effect from sitting for more than eight hours when compared with less than four hours (1.04 (0.99 to 1.10)). However, sitting for more than eight hours rather than four increased the risk of death in those who did the least amount of moderate activity (around five minutes a day) by around a quarter (1.27 (1.22 to 1.31)).
Watching television for three hours or more a day was associated with increased mortality except in people who did at least one hour of moderate activity a day; however, even their mortality increased if they watched television for at least five hours a day (1.16 (1.05 to 1.28)).
“There has been a lot of concern about the health risks associated with today’s more sedentary lifestyles,” said the lead author, Ulf Ekelund, of the Norwegian School of Sports Sciences and the University of Cambridge, UK. “Our message is a positive one: it is possible to reduce—or even eliminate—these risks if we are active enough, even without having to take up sports or go to the gym.”
He added, “For many people who commute to work and have office based jobs, there is no way to escape sitting for prolonged periods of time. For these people in particular, we cannot stress enough the importance of getting exercise, whether it’s getting out for a walk at lunchtime, going for a run in the morning, or cycling to work.
“An hour of physical activity per day is the ideal, but if this is unmanageable, then at least doing some exercise each day can help reduce the risk.”