Sitting down on the job increases risk of early death

Office workers beware: sitting for more than 10 hours a day causes the risk of cardiovascular disease and early death to rise sharply, even if you meet the recommended levels of exercise, research shows.

Researchers looked at data from nearly 90,000 study participants from Britain's biobank – the group had an average age of 62 and were 56.5 per cent women. Participants submitted data from a wrist-worn device that captured movement over seven days, with the average daily sedentary time marked at 9.4 hours.

Data showed that after an average follow-up of eight years, 3,638 people (4.9 per cent) developed atrial fibrillation, 1,854 (2.1 per cent) suffered from heart failure, 1,610 (1.84 per cent) developed myocardial infarction and 846 (0.94 per cent) died of cardiovascular causes.

Experts say exercise is only a small fraction of overall daily activity and the current guidelines do not provide specific guidance on sedentary behaviour.

“Our findings support cutting back on sedentary time to reduce cardiovascular risk, with 10.6 hours a day marking a potentially key threshold tied to higher heart failure and cardiovascular mortality,” said Shaan Khurshid, a cardiologist at the Massachusetts General Hospital and co-senior author of the study, published in Journal of the American College of Cardiology. “Too much sitting or lying down can be harmful for heart health, even for those who are active.”

Researchers say the risk of heart conditions increases gradually, but it rises exponentially after people have been sitting down for about 10 hours. Charles Eaton, director of the Department of Family Medicine at Brown University, said the use of wearable devices showed exercise was significantly overestimated by self-report and sedentary behaviour was underestimated.

He said replacing 30 minutes of excessive sitting time each day with any type of physical activity could lower heart health risks. Adding moderate-to-vigorous activity cut the risk of heart failure by 15 per cent and cardiovascular mortality by 10 per cent. Light activity also made a difference by reducing heart fibrillation risk by 6 per cent and cardiovascular mortality by 9 per cent.

“This study adds to the growing evidence of a strong link between sedentary behaviour and cardiovascular health,” said Harlan Krumholz, professor at the Yale School of Medicine. “The findings strongly suggest that we need to get people moving to promote better health.”

Researchers did not study where or why people were sitting or lying down for extended periods. They also say devices worn on the wrist do not always detect posture accurately and so may misidentify time spent standing as sedentary time.