How Much TV is Bad for You?

They found every hour in front of the TV was associated with an 11% increased risk of death from all causes, a 9% higher risk of cancer death, and an 18 percent increased risk of cardiovascular disease (CVD) related death.

This research provides another clear link between too much sitting and death from disease," said lead researcher David Dunstan, head of the Physical Activity Laboratory at the Baker IDI Heart and Diabetes Institute in Victoria, Australia.

"The findings have serious implications for Americans and Australians when you consider that aside from sleeping, watching television is the behavior that occupies activity of four hours viewing a day," he added.

The good news is research has shown that moving the muscles frequently throughout the day is one of the most effective ways of managing weight and protecting against disease, Dunstan added.

"We tend to underestimate the value of incidental, non-sweaty activity throughout the day when we are either not sleeping or exercising -- the more you move, the greater the benefits for health," he noted.

Dunstan pointed out that while obesity can add to these problems, even normal-weight people can have increases in blood sugar and cholesterol if they sit too much.

For the study, Dunstan's team collected data on the lifestyles of 8,800 healthy men and women aged 25 years and older. In addition to lifestyle habits, the researchers tested participants' cholesterol and blood sugar levels. Over more than six years of follow-up, 284 people died. Among these deaths, 87 were due to cardiovascular disease and 125 from cancer.

The participants were grouped into three TV-watching categories: those who watched less than two hours a day; those who watched two to four hours a day; and those who watched more than four hours a day.

The researchers found that every hour of daily TV watching increased the risk of dying from any cause by 11 percent. For cardiovascular diseases the increased risk was 18 percent, and for cancer it was 9 percent. Compared with those who watched less than two hours per day, those who watched TV for more than four hours each day had an 80 percent increased risk of dying early from cardiovascular disease and a 46 percent increased risk of dying from any cause.

The association between TV watching and death remained even when the researchers took into account risk factors for cardiovascular disease such as smoking, high blood pressure, high cholesterol, unhealthy diet, excessive weight and exercise.

Although the study was done in Australia, the findings are applicable to Americans, Dunstan said. Average daily television watching is about three hours in Australia and the United Kingdom, and up to eight hours in the United States, where many people are either overweight or obese, he noted.

"What we are now starting to understand is that the risks associated with sedentary behavior are not necessarily offset by doing more exercise," Dunstan said.

"In other words, irrespective of how much exercise you do, if you sit watching television for four hours on a daily basis you still have a substantially increased risk of early death from all causes and a much greater risk of cardiovascular disease," he said.

David Bassett Jr., a professor of health and exercise science at the University of Tennessee, said that "when one looks at time trends in physical activity over the past century, it is clear that people are doing more structured, purposeful exercise than before."

However, what has changed is that people are doing less walking, household chores and manual labor than in the past, he said. "We are also spending more time in sedentary activities like television watching, computer use and desk jobs," Bassett explained.

"This study adds to a growing body of evidence that the amount of time spent in sedentary activity, as distinct from the amount of time spent in purposeful exercise, can affect your health," he said.