Latest news: 28 July.

A global study of more than one million people including participants in the Sax Institute’s 45 and Up Study finds that doing at least one hour of physical activity per day, such as brisk walking or cycling for pleasure, may eliminate the increased risk of death associated with sitting for eight hours a day.

The findings come from a new four-paper series published in The Lancet and launched ahead of the Summer Olympic Games. The Series’ authors  warn there has been too little progress in tackling the global pandemic of physical inactivity since the 2012 Olympics, with a quarter of adults worldwide still failing to meet current recommendations on physical activity.

In one paper, researchers analysed data on sedentary behaviour from 16 studies involving a total of more than one million people. They included a 2012 study of more than 220,000 NSW participants in the 45 and Up Study, which revealed adults who sat 11 or more hours per day had a 40% increased risk of dying in the next three years compared with those who sat for fewer than four hours a day.

Time sitting vs time being active

The research team, which included the University of Sydney’s Professor Adrian Bauman and previous Sydney University researchers Associate Professor Hidde van der Ploeg and Tien Chey, explored how many hours of daily physical activity would be required to eliminate the association between prolonged sitting time and increased risk of death. Examples of physical activity were brisk walking at 5.6 km/hr or cycling for pleasure at 16 km/hr.

Their meta-analysis showed that people who sat for eight hours a day but were highly physically active had a much lower risk of death compared to people who sat for fewer hours a day, but were not physically active.

In fact, the increased risk of death associated with sitting for eight hours a day was eliminated for people who did at least one hour moderate intensity physical activity per day. The greatest risk of death was for people who sat for long periods of time and were inactive.

The researchers also looked at time spent watching TV per day – a specific type of sedentary behaviour – in six studies involving about 500,000 people. They found sitting watching TV for more than three hours per day was associated with an increased risk of death in all activity groups, except the most active. Among the most active people, mortality was significantly increased only in those who watched five or more hours of TV per day.

The authors said that WHO guidelines recommended that adults do at least 150 minutes of physical activity per week, which was much lower than the 60‒75 mins per day identified in the analysis as beneficial to offset prolonged sitting time.

“These results provide further evidence on the benefits of physical activity, particularly in societies where increasing numbers of people have to sit for long hours for work and may also inform future public health recommendations,” the authors wrote.

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