WASHINGTON, (AFP) - A review of published studies in the past 40 years has shown a higher risk of diabetes, heart problems and early death among people who watch lots of television, US researchers said Tuesday.

The results of the meta-analysis performed by scientists at the Harvard School of Public Health are published in the June 15 issue of the Journal of the American Medical Association.

More than two hours per day of TV-watching boosted risk of type two diabetes and heart disease, while more than three hours a day increased a person's risk of dying prematurely.

Each two-hour increment in viewing per day was linked to a 20 percent higher risk for type two diabetes; a 15 percent increased risk for fatal or nonfatal cardiovascular disease; and a 13 percent higher risk for all-cause mortality.

"While the associations between time spent viewing TV and risk of type two diabetes and cardiovascular disease were linear, the risk of all-cause mortality appeared to increase with TV viewing duration of greater than three hours per day," the study said.

The habit of plunking oneself down in front of the television and watching for hours makes up about five hours of daily activity on average in the United States, but is also a prevalent practice around the world.

In Europe, people spend about 40 percent of their daily free time – or three hours -- in front of the tube, and in Australia the average is 50 percent of daily free time or four hours, the study said.

"The message is simple. Cutting back on TV watching can significantly reduce risk of type two diabetes, heart disease, and premature mortality," said senior author Frank Hu, professor of nutrition and epidemiology at Harvard.

"We should not only promote increasing physical activity levels but also reduce sedentary behaviors, especially prolonged TV watching."