A study of nearly 9,000 Australian adults has reported that people who watched 4 hours of TV a day or more were 46% more likely to die within the next six and a half years than those who watched less than 2 hours a day. Each one hour increase in daily television viewing increased the risk of death from any cause by 11% and death by cardiovascular disease by 18%.
Previous studies have suggested that sedentary behaviour is associated with a mortality risk. Furthermore, surveys in the US and the UK indicate that, aside from sleeping, lounging around watching television takes up the most of our time at home – about 3 hours a day in the UK and up to 8 hours a day in the US, apparently.
This study, published in the journal Circulation, examined 8,800 adults aged 25 years or older who were in the Australian Diabetes, Obesity and Lifestyle Study (AusDiab). All participants were interviewed at the start of the study to find out their lifestyle habits, medical history, and the amount of time they had spent watching television or videos in the previous 7 days.
About six and a half years later, on average, mortality status and cause of death for each participant was established from the Australian National Death Index.
Each one hour increase in television viewing time was associated with an 11% increase in the risk of death from any cause and an 18% increase in the likelihood of death related to cardiovascular disease. However, these relationships were attenuated once other factors like medical history and smoking habits were taken into account, but the association between TV time and death from any cause did remain important. The link between television viewing time and cancer mortality was negligible though.
Strikingly, the risk of mortality was much higher in people who watched at least 4 hours of TV a day than in those who watched less than 2 hours – the risk of death from any cause was 46% higher and the risk of death from cardiovascular disease was a whopping 80% more.
Individuals who watched 4 hours of TV a day or more were more likely to be a current or ex-smoker, have a poor diet, be overweight, or have raised blood pressure than those who watched less than 2 hours daily – that is, they seemed generally less healthy and, in theory, would be more likely to just drop dead. However, none of these factors affected the associations between television viewing and mortality.
The public health implications of this study are pretty serious – get TV addicts to cut their viewing in half and they could considerably reduce their risk of death over the next 6 years or so. As the authors say, “our findings suggest that reducing time spent watching television (and possibly other prolonged sedentary behaviors) may also be of benefit in preventing CVD and premature death.” They recommend that as well as promoting exercise, public health bodies should also “focus on reducing sitting time, particularly prolonged television viewing.”
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Dunstan D et al. (2010) Television Viewing Time and Mortality: The Australian Diabetes, Obesity and Lifestyle Study (AusDiab). Circulation 121 (3): 384-391. DOI: 10.1161/CIRCULATIONAHA.109.894824