Prolonged sedentary behaviour increases the risk of heart disease and premature death, even among people who meet recommended exercise guidelines, a new study has revealed, highlighting the importance of minimising sedentary time for health.

The study led by US researchers has found that individuals whose sedentary periods exceeded 10 hours and 36 minutes a day had a 40 per cent increased risk of heart failure and a 62 per cent increased risk of cardiovascular mortality.

Their findings, published this week in the Journal of the American College of Cardiology, suggest that avoiding sedentary time beyond 10.6 hours a day should be a “minimum target” or threshold for heart health gains and even fewer sedentary
hours may bring additional benefits.

Current cardiovascular health guidelines prescribe at least 150 minutes of moderate to vigorous physical activity (MVPA) per week, but the new study has indicated that meeting MVPA requirements alongside long sedentary periods is insufficient to reduce
the risk.

Sedentary behaviour refers to activity marked by low energy expenditure such as sitting, reclining, or lying down, in contrast to light physical activity such as a gentle walk.

“Our data supports the idea that it is always better to sit less and move more to reduce heart disease risk,” said Shaan Kurshid, an electrophysiologist and a faculty member at the Massachusetts General Hospital, Boston, the study’s co-leader.

“Avoiding excessive sitting is especially important for lowering the risk of heart failure and cardiovascular death,” Kurshid said in a media release by the hospital.

The researchers found what they have described as a “dose-response relationship” — the greater the number of days the 10.6-hour threshold is exceeded, the greater the risks. One additional day with a sedentary period exceeding 10.6 hours meant a 7 per cent increased risk of heart failure and a 10 per cent increased risk of premature cardiovascular death.

“Many of us spend the majority of our waking time sitting,” said Ezimamaka Ajufo, a cardiology fellow at the Brigham and Women’s Hospital, Boston, and the study’s first author. “While there is a lot of research on the importance of physical activity, we know relatively little about the potential consequences of sitting too much beyond a vague awareness that it might be harmful,” Ajufo said in the media release.

The researchers analysed the cardiovascular health of over 89,500 study participants in the UK who were invited to wear accelerometers — electronic devices that record movements — for seven days between February 2013 and December 2015. The accelerometer signals were classified into one of four activities — sleep, sedentary, light physical activity and MVPA.

They found that sedentary behaviour was associated with higher risks for all four measures of heart health examined: atrial fibrillation — a disorder marked by irregular heartbeat — heart failure, heart attacks and premature death from cardiovascular causes.

“Many of us sit a lot and think that if we can get out at the end of the day and do some exercise, we can counterbalance it,” Ajufo said. “However, we found that it is more complex than that.”

The study found that some of the negative effects of sedentary behaviour persisted even among participants who had achieved the recommended 150 minutes or more MVPA per week.

The risk of atrial fibrillation and heart attacks could be nearly eliminated through physical activity, but physical activity could only partially offset excess risks of heart failure and cardiovascular mortality.

“Exercise is critical, but avoiding excessive sitting appears separately important,” Patrick Ellinor, a cardiologist and the study’s second co-leader, said in the media release.