Too much sitting increases the risk of early death: But how much?

Advances in technology over the past few decades have reduced the need and desire for people to move. Much of the world’s population sits for long periods throughout the day, whether in front of a computer at work or in front of the television at home. Given that the human body is designed to move, all that sitting is clearly bad for our health. A new study from the University of California, San Diego (UCSD) confirms this – and then some.

A total of 5856 female participants aged 63 to 99 were asked to wear an activity tracker on their hip for seven days at the start of the study. The researchers then followed them for a decade, during which time 1733 participants died. The researchers used artificial intelligence to work out how much time the participants spent sitting from the activity monitor, and then linked this to their risk of death. The data showed that participants who sat for more than 11 hours a day had a 57 per cent higher risk of dying during the study period than those who sat for less than nine and a half hours a day.

But regular exercise will counteract the health risks of too much sitting, right? Not according to the UCSD study. The risk of early death was still there, even with higher amounts of moderate to vigorous exercise. A 2019 study also found that more exercise didn’t reverse the risk of diseases like type 2 diabetes, heart disease and stroke that come with too much sitting.

However, an Australian study found that walking between 9000 and 10500 steps a day lowered the risk of premature death, even in people who sat a lot.

The conflicting results could be explained by the fact that the activity monitors in the UCSD study were worn on the hip, while those in the Australian study were worn on the wrist, which could lead to different estimates of sitting time.

The Australian study also didn’t use special software to work out when people were sitting or standing in the activity monitor data, so standing could have been mistaken for sitting. For example, if a participant stood still for half an hour, this would be counted as half an hour of sitting. This could mean that the Australian study underestimated the amount of time its participants spent sitting.

The evidence from the UCSD study seems to be better, highlighting the need to sit less. Current World Health Organization guidelines support this, recommending that adults limit the amount of time they sit and break up long periods of sitting.
How much sitting is too much?

So how much sitting is too much? The UCSD study says 11 hours a day. Other studies say as little as seven hours a day could be too much. There’s also a lot of research that says you shouldn’t sit for more than 30 minutes at a time because it can raise your blood sugar and blood pressure.

So what can you do to avoid sitting for too long?

A sit-stand desk might help if you’re an office worker. Or you could get up and move around between tasks or while on the phone. At home, you could stand up during commercial breaks or while the kettle is boiling. Some smart devices and wearables will also buzz if you sit for too long.

But what if you can’t stand or walk? A 2020 study found that small bursts of arm exercise (for example, two minutes every 20 minutes) lowered blood glucose levels in wheelchair users. As long as you’re doing something that means you’re not sitting still, there are health benefits to be had.

Daniel Bailey, Senior Lecturer in Sport, Health and Exercise Science, Brunel University London