Although many previous studies have shown that too much sedentary time increases the risk of a variety of diseases, including type 2 diabetes, non-alcoholic fatty liver disease, heart disease, stroke, and high blood pressure, as well as contributing to an increase in waist measurement and an increased mortality risk, until now there was no number attached to the amount of time an individual could be sedentary for before it begins to have a negative effect on health.
To look at an association between the number of sedentary hours and the risk of cardiovascular disease, a team of researchers from several institutions throughout the USA analyzed data from the EMBASE and MEDLINE databases.
The data spanned an 11-year period and 720,425 participants in total who together had a mean age of 54.5 years. Researchers also included lying down in their definition of sedentary time.
From their analysis the team found that sitting for 10 hours a day was the number of hours of sedentary time at which an increased risk of cardiac problems becomes noticeable.
Although the number may sound high, the team believe it is probably easily achieved by most people. Office workers, for example, may sit down at work for seven to eight hours a day, sitting down for an hour at lunch, and then are very possibly sitting down again while commuting to and from work. And when many people arrive home they then sit again, to eat dinner or partake in activities such as browsing the internet or watching TV.
The team also found that those in the highest sedentary time category of 12.5 hours on average a day were 14 percent more likely to experience heart problems than those who sat for just 2.5 hours on average each day.
However no increased risk was found for those who were in the intermediate level of sedentary time category, classed as 7.5 hours a day, with the team concluding that the increased risk of cardiovascular problems is only seen at higher levels of sedentary time from 10 hours a day and upwards.
Although the researchers suggest that for office workers it is possible to reduce the risk of cardiovascular disease by using equipment that encourages more standing and physical activity, such as stand-up work stations, it is still not known whether exercise in between prolonged periods of sitting offsets the health risks of sedentary time.
The findings can be found online in the journal, JAMA Cardiology.