Watching an hour of TV after the age of 25 can shorten the viewer's life by just under 22 minutes, according to researchers in Australia.
The AFP news agency said scientists at the School of Population Health at the University of Queensland studied 11,000 Australian adults who were aged at least 25 in the year 2000.
The academics checked their data against an estimate from 2008 that Australians aged 25 or above watched TV for 9.8 billion hours. This was associated with the loss of 286,000 years of life, the AFP said.
An extrapolation of these figures found that a single hour of TV was responsible for the loss of just under 22 minutes of life, the news agency reported.
Smoking two cigarettes has approximately the same effect.
The problem is not actually TV itself but the lack of activity by the viewer for long periods, the researches said. Cardiovascular disease, diabetes, excess weight and other health problems are associated with a sedentary lifestyle.
Lennert Veerman, who was involved in the study, said the research showed watching television was "in the same ballpark as smoking and obesity," according to a report in The Guardian newspaper.
"While smoking rates are declining, watching TV is not, which has implications at a population level," he said according to the report.
A previous study in Australia found there was an 8 percent greater risk of dying prematurely associated with watching an hour of TV a day.
"We've taken that study and translated it into what it means for life expectancy in Australia given how much TV we watch," Veerman said.
The latest research was published in the British Journal of Sports Medicine.
Meanwhile, a large study in Taiwan found that doing just 15 minutes of moderate exercise a day might add three years to your life.
Lead researcher Chi Pang Wen of Taiwan's National Health Research Institutes said dedicating 15 minutes a day to a moderate form of exercise, like brisk walking, would benefit anyone.
"It's for men, women, the young and old, smokers, healthy and unhealthy people. Doctors, when they see any type of patient, this is a one-size-fits-all type of advice," Wen told Reuters in a telephone interview.
Wen and colleagues, who published their findings in medical journal The Lancet on Tuesday, tracked over 416,000 participants for 13 years, analyzing their health records and reported levels of physical activity each year.
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