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August 17, 2011

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Is too much TV as dangerous as smoking?

Aug. 16, 2011
Courtesy of BMJ Publishing Group
and World Science staff

Could tele­vi­sions soon come with stomach-churning warn­ing la­bels like those on cig­a­rette packs? A new study of Aus­tralians in­di­cates that watch­ing TV for an av­er­age of six hours a day could short­en life ex­pect­an­cy by al­most five years, ri­val­ing smok­ing in sev­er­ity as a risk fac­tor for dis­ease.

To put it an­oth­er way, eve­ry hour of TV watched af­ter age 25 may slice about 22 min­utes off your life, an effect equi­val­ent to that of two cigarettes, said the re­search­ers, whose find­ings are pub­lished on­line in the Brit­ish Jour­nal of Sports Med­i­cine.
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 part of sed­en­tary ac­ti­vity, but its im­pact on life ex­pect­an­cy has­n’t been as­sessed, say the au­thors, J. Lennert Veer­man of the Uni­vers­ity of Queens­land in Aus­tral­ia and col­leagues.

They used pre­vi­ously pub­lished da­ta on the rela­t­ion­ship be­tween TV view­ing time and death based on the Aus­tral­ian Di­a­be­tes, Obes­ity and Lifestyle Study, a re­cent sur­vey of 11,000 Aus­tralians aged 25 or old­er. The re­search­ers al­so used Aus­tral­ian na­tional popula­t­ion and mor­tal­ity fig­ures for 2008.

The au­thors then cre­at­ed a “risk frame­work” for the Aus­tral­ian popula­t­ion in 2008, based on sur­vey par­ti­ci­pants’ an­swers to ques­tions about the to­tal amount of time they had spent in the pre­vi­ous week watch­ing TV or videos. The au­thors es­ti­mat­ed that Aus­tral­ian adults aged 25 and old­er spent a to­tal of 9.8 bil­lion hours in front of the tube. This in turn led them to cal­cu­late that some­one who spends a life­time av­er­age of six hours a day watch­ing TV can ex­pect to live just un­der five few­er years than some­one who does not watch TV.

Oth­er re­search has found that life­long smok­ing is as­so­ci­at­ed with the short­ening of life ex­pect­an­cy by more than four years af­ter the age of 50, with the av­er­age loss of life from one cig­a­rette cal­cu­lated to be 11 min­utes—equivalent to half an hour of TV watch­ing, ac­cord­ing to the au­thors' frame­work.

"Sub­stantial loss of life may be as­so­ci­at­ed with pro­longed TV view­ing," the au­thors wrote. "While we used Aus­tral­ian da­ta, the ef­fects in oth­er in­dus­t­ri­alised and de­vel­op­ing coun­tries are likely to be com­pa­ra­ble, giv­en the typ­ic­ally large amounts of time spent watch­ing TV and si­m­i­lar­i­ties in dis­ease pat­terns."

They con­clud­ed: "If these [fig­ures] are con­firmed and shown to re­flect a caus­al as­socia­t­ion, TV view­ing is a pub­lic health prob­lem com­pa­ra­ble in size to es­tab­lished be­havioural risk fac­tors."

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Could televisions soon come with stomach-churning warning labels like those on cigarette packs? A new study of Australians indicates that watching TV for an average of six hours a day could shorten life expectancy by almost five years, rivaling smoking in severity as a risk factor for disease. To put it another way, every hour of TV watched after age 25 may slice about 22 minutes off your life, said the researchers, whose findings are published online in the British Journal of Sports Medicine. 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 part of sedentary activity, but its impact on life expectancy hasn’t been assessed, say the authors, J Lennert Veerman of the University of Queensland in Australia and colleagues. They used previously published data on the relationship between TV viewing time and death based on the Australian Diabetes, Obesity and Lifestyle Study, a recent survey of 11,000 Australians aged 25 or older. The researchers also used Australian national population and mortality figures for 2008. The authors then created a “risk framework” for the Australian population in 2008, based on survey participants’ answers to questions about the total amount of time they had spent in the previous week watching TV or videos. The authors estimated that Australian adults aged 25 and older spent a total of 9.8 billion hours in front of the tube. This in turn led them to calculate that someone who spends a lifetime average of six hours a day watching TV can expect to live just under five fewer years than someone who does not watch TV. Other research has found that lifelong smoking is associated with the shortening of life expectancy by more than four years after the age of 50, with the average loss of life from one cigarette calculated to be 11 minutes—equivalent to half an hour of TV watching, according to the authors' framework. "Substantial loss of life may be associated with prolonged TV viewing," the authors wrote. "While we used Australian data, the effects in other industrialised and developing countries are likely to be comparable, given the typically large amounts of time spent watching TV and similarities in disease patterns." They concluded: "If these [figures] are confirmed and shown to reflect a causal association, TV viewing is a public health problem comparable in size to established behavioural risk factors."