Television viewing: a risk factor for death?
It is fascinating which health research grabs the media’s attention and which does not. The problem is twofold: there are so many journals and reporters are lazy and follow only the Lancet and the BMJ. The International Journal of Epidemiology published a great study from Cambridge this week, totally unnoticed by the media, showing that TV viewing time is independently associated with all-cause mortality and cardiovascular mortality. It deserves particular attention since I invested in a Sky TV subscription last month.
We already know that TV viewing is epidemic (55% of the waking day in the US!!) and is associated with risk factors for heart disease independent of physical activity. In other words, the harmful effect of TV watching is not just through reduced physical activity. Now this study adds that TV watching is associated with death in men and women, particularly from cardiovascular disease, again independent of physical activity.
In a prospective study of over 13000 men and women over 10 years, the authors gathered data about self-reported daily TV watching, risk factors, medications and cause of death. The clever way they present their data makes it even more compelling. Each 1 hour per day extra of TV watching was associated with a 4% increase in all-cause mortality and a 7% increase in cardiovascular mortality, but was not associated with cancer mortality. These results were calculated as hazard ratios. Importantly, they were independent of all major confounding factors: gender, age, education, smoking, alcohol, medication, diabetes or family history of cardiovascular disease and cancer, BMI and physical activity.
My favourite stat from this paper uses the population-attributable fraction (PAF). The PAF tells you how much reduction in the outcome (death in this case) would occur if exposure to a risk factor (TV watching time) were reduced to an alternative ideal exposure scenario. This study shows that all-cause mortality would be reduced by 5.4% if people reduced their TV viewing from >3.6 hours per day to <2.5 hours per day. More studies should report their numbers in a way so that policymakers can easily access and use like this.
Should we now be including TV watching as a risk factor for heart disease and aim to reduce it in CVD prevention guidelines? As a society, should we be targetting Rupert Murdoch and other players in the massive TV industry to take more responsibility for disease in the same way we target the tobacco and food industries? The worst bit is that I am tied into this Sky contract for a year now.