Watching TV for an average of six hours a day could shorten your life expectancy by almost five years, indicates research in the British Journal of Sports Medicine.
The impact rivals that of other well known behavioral risk factors, such as smoking and lack of exercise, they say.
Sedentary behavior, as distinct from too little exercise, is associated with a higher risk of death, particularly from heart attack or stroke. Watching TV accounts for a substantial amount of sedentary activity, but its impact on life expectancy has not been assessed, say the authors.