How many hours of sitting may increase the risk of premature death?

A new study conducted by the University of California, San Diego (UCSD) has confirmed that sitting for long periods every day is harmful to our health.

In the study, 5,856 female participants, between the ages of 63 and 99, were asked to wear an activity monitor on their hip for 7 days initially. Their cases were followed for a decade, during which 1,733 participants died.

The researchers used artificial intelligence to determine how much time participants spent sitting by monitoring activity, and then linked this to the risk of death.

The data showed that participants who spent more than 11 hours sitting per day were 57% more likely to die during the study period, compared to women who sat less than 9 and a half hours per day.

The risk of early death persisted even with more moderate to vigorous exercise.

This contradicts an Australian study that found that walking between 9,000 and 10,500 steps per day reduces the risk of early death, even for people who sit a lot.

The researchers say that attaching activity monitors to the hip in the UCLA study and to the wrist in the Australian study, which may lead to different estimates of sitting time, may explain the contradictory results.

The Australian study also did not use any special activity monitoring data software to determine when participants stood or sat.

For example, if a participant remained still for half an hour, this would be counted as half an hour of sitting, meaning the Australian study underestimated the time participants spent sitting.

The evidence from the University of California study appears to be better, highlighting the need to reduce sitting. Current guidelines from the World Health Organization also support this, recommending that adults should limit the amount of sitting time and break up long periods of sitting.