Doctors should tell patients to not only exercise more but also sit less, the researchers say. (Canadian Press)

The longer people spend sitting, the more likely they are to die prematurely, regardless of their fitness levels, a finding that has serious public health implications, researchers say.

In the May issue of the journal Medicine and Science in Sports and Exercise, researchers found a greater risk of mortality linked with higher amounts of time spent sitting in more than 17,000 Canadian men and women.

The link held after taking into account physical activity levels outside of work, body mass index, age, sex, smoking and drinking alcohol.

"I don't think it's a very rosy future," said the study's lead author, Claude Bouchard, a retired professor from Quebec City who is now executive director at the Pennington Biomedical Research Center in Baton Rouge, La.

"If we combine that [time spent sitting at work] with the growing prevalence of obesity, it's going to mean that just about every developed society is going to be faced with a health care cost bill that has the potential to bankrupt the finances of all of these developed countries."

In the study, the researchers concluded the results support public health calls to limit sedentary time.

"The findings of the study also support that physicians should counsel patients to not only increase their level of physical activity and maintain a normal body weight but to reduce the amount of time they spend being sedentary in general and sitting in particular."

Participants who were classified as active (getting at least 30 minutes of moderate-intensity physical activity such as brisk walking five days a week) had a lower overall risk of mortality over the 12 years of follow up, the team found.

Only five per cent of Canadian adults compensate for the time they sit at work through exercise. Even among this group, the risk of premature death escalated depending on the amount of sedentary time in their day.

Walk away from your seat

The mortality risk was 1.54 times higher among those who spent almost all of the day sitting compared with those who spent almost no time sitting, the researchers found.

During the 12 years of follow-up, 1,832 deaths were recorded, including 759 from cardiovascular disease, 547 from cancer and 526 from other causes.

The link between time spent sitting and higher risk of mortality applied only in the case of the cardiovascular deaths and deaths overall but not those from cancer.

The finding is important since researchers suspected that deaths related to sitting would occur through cardiovascular disease.

Laboratory studies suggest that time spent sitting is associated with major disturbances in how the body metabolizes fuels such as glucose and lipids, Bouchard noted.

Taking breaks from sitting helps to normalize this physiology, he added.