By Steven Reinberg

HealthDay Reporter

MONDAY, Jan. 11 （HealthDay News） -- Every hour spent watching TV each day may increase your risk of an early death from cardiovascular disease by as much as 18 percent, Australian researchers say.

What's on the television is not the problem; it's the time spent sitting while watching.

"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.

"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.

The report was released online Jan. 11 in advance of publication in an upcoming print issue of Circulation.

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.

Experts agreed that to stay healthy you need to keep on the move.

Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles, said that "regular exercise has been consistently demonstrated to result in improved cardiovascular health and lower risk of heart attacks, stroke, diabetes and premature death."

He added that "reducing time spent inactive may be of benefit in reducing the risk of cardiovascular disease and should be considered as part of a comprehensive approach to improve cardiovascular health."

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.