A study using UK Biobank data has found that if adults spent no more than two hours watching TV each day, they could minimise their exposure to the health risks associated with TV.
Researchers examined lifestyle and demographic data from 490,966 UK Biobank participants and linked their data to national routine death and disease registries.
Overall health risks from diseases including cancers and cardiovascular disease were associated with viewing TV for 2 hours or less per day. Further analysis estimated that 6% of all-deaths and 8% of cardiovascular deaths were attributable to TV time. They also showed that potentially, if all participants limited TV time to 2 hours a day, 5.62% of all deaths and 7.97% of deaths due to cardiovascular disease could have been prevented or delayed.
The study also examined the potential benefits of substituting TV time with healthier activities such as walking. They found that those people who would benefit most from replacing longer periods of TV time with more time spent doing healthier activities, are those who currently only spend very small amounts of their day doing those healthier activities.
Current physical activity guidelines in UK encourage 150 minutes of moderate physical activity or 75 minutes of vigorous activity a week. On the other hand, current sedentary guidelines lack specific advice, and only suggest that people limit the time they spend sitting. There is currently no recommendations as to what might be a low risk amount of time to spend sitting watching TV each day.
In order to reduce the chance of the results being due to reverse causality (where poor health leads to increased TV time) participants with non-communicable disease, cardiovascular disease and cancer were excluded. Similarly, the researchers excluded all those with an adverse health event within two years of recruitment.
"This study adds more weight to the evidence that more time spent watching TV is likely to be detrimental to health. Our study suggests limiting TV time could delay or prevent a lot of adverse health. However, there is still more work to be done before we can make firm TV time recommendations. TV time is just one of a number of potentially sedentary behaviours, which also includes screen time watching videos on your phone, which may all contribute to adverse health outcomes. Also, there are many other contributory factors, such as unhealthy snacking and lower socioeconomic status, that are also strongly associated with both TV time and poor health outcomes. Further research is needed to understand all these factors and inform future advice and guidelines."
Dr Hamish Foster, University of Glasgow’s Institute of Health and Wellbeing, Lead Author