Watching too much television or playing computer games damages your heart regardless of how much exercise you do, scientists have warned.
The risk of heart disease and premature death from any cause doubled for those spending more than fours hours a day glued to a screen, it was claimed.
Metabolic factors and inflammation may be partly to blame, the report said.
Research revealed those who devote more than four hours watching television, surfing the web, or playing compuer games are more than twice as likely to have major cardiac problems.
Dr Emmanuel Stamatakis of University College London’s Department of Epidemiology and Public Health said: “People who spend excessive amounts of time in front of a screen – primarily watching TV – are more likely to die of any cause and suffer heart-related problems.
“Our analysis suggests that two or more hours of screen time each day may place someone at greater risk for a cardiac event.”
The study was the first to examine the association between screen time and fatal and non-fatal heart attacks – found there was a 48 per cent increased risk of all-cause mortality and an approximately 125% increase in risk of cardiovascular events in those spending more than four hours
The risks were irrespective of factors such as smoking, hypertension, BMI, social class, and even exercise.
The scientists called for recreational guidelines to be issued because a majority of working age adults spend long periods being inactive while commuting or being slouched over a desk or computer.
Dr Stamatakis said: “It is all a matter of habit. Many of us have learned to go back home, turn the TV set on and sit down for several hours it’s convenient and easy to do.
“But doing so is bad for the heart and our health in general.
“And according to what we know so far, these health risks may not be mitigated by exercise, a finding that underscores the urgent need for public health recommendations to include guidelines for limiting recreational sitting and other sedentary behaviours, in addition to improving physical activity.”
The team found biological mediators also appeared to play a role.
Data indicate that one fourth of the association between screen time and cardiovascular events was explained collectively by C-reactive protein (CRP), body mass index, and high-density lipoprotein cholesterol suggesting that inflammation and deregulation of lipids may be one pathway through which prolonged sitting increases the risk for cardiovascular events.
CRP, a well-established marker of low-grade inflammation, was approximately two times higher in people spending more than four hours of screen time per day compared to those spending less than two hours a day.
The next step would be to try to uncover what prolonged sitting does to the human body in the short and long-term, whether and how exercise can mitigate these consequences, and how to alter lifestyles to reduce sitting and increase movement and exercise.
The present study included 4,512 adults who were respondents of the 2003 Scottish Health Survey. A total of 325 all-cause deaths and 215 cardiac events occurred during an average of 4.3 years of follow up.
The findings are published in the Journal of the American College of Cardiology.