Today’s post comes from Dr Katrien Wijndaele, University of Cambridge, UK. More information on Dr Wijndaele can be found at the bottom of this post.
Excessive leisure screen time, including TV viewing, is highly prevalent in a large proportion of adults on a daily basis, without signs of decline (3, 6). It is also the type of sedentary behaviour most strongly and consistently associated with the development of chronic disease and premature mortality (4, 8). Reducing leisure screen time is therefore a potentially important public health target. However, part of the protective effect of reducing screen time also depends on what type of activity it is replaced by (5). So far no studies looked into which leisure-time activities could be healthy alternatives for screen time to prevent premature mortality. This would be important knowledge to fully inform public health guidance on screen time reductions in adults. We therefore asked this question in our research article Mortality risk reductions from substituting screen time by discretionary activities, published recently by Medicine & Science in Sports & Exercise (9).
In almost 0.5 million middle-aged adults without major chronic disease, who were followed for almost 8 years as part of the UK Biobank cohort (1), we estimated the risk reduction for all-cause mortality associated with replacing leisure screen time by different types of discretionary activity, using iso-temporal substitution modelling. We found that replacing small amounts of screen time (i.e. 30 minutes/day) into everyday activities, such as leisurely walking or DIY (i.e. home maintenance and improvement activities) of the same duration, can result in important mortality benefits. The strongest effect estimates were found when modelling replacement of TV viewing. Everyday activities may therefore be important behavioural change targets for adults for whom taking up more organized exercise activities and vigorous sports instead of screen time (which showed stronger mortality benefits) initially seems less feasible.
To further inform public health guidance, we also examined the reduction in all-cause mortality incidence associated with each of these behavioural change scenarios. We estimated that 4% (30 minutes/day substitution of total screen-time into light DIY) to almost 15% (30 minutes/day substitution of TV viewing into strenuous sports) of premature deaths in the UK could be avoided, through such substitutions (assuming causality).
Given the ubiquitous nature of leisure screen time, the achievability of the examined behavioural change options and the substantial mortality benefits estimated, specific guidelines on reductions in leisure screen time, which have so far been mainly implemented for children (7), could also be considered for adults, to complement emerging guidelines on occupational sitting (2). Importantly, these could not only recommend reductions in leisure screen time but also substitution by alternative healthy activities, which can take place in and around the home and during leisure time.
The full results and interpretation of these findings can be found here.
About the author: Katrien Wijndaele is a Senior Investigator Scientist at the MRC Epidemiology Unit, University of Cambridge, UK. Her primary research interest lies in the potential health consequences of prolonged sitting in adults and children, with an additional focus on sedentary behaviour surveillance, measurement and intervention development. She is also chairing the Sedentary Behaviour Council of the International Society for Physical Activity and Health.
1. Allen, N., C. Sudlow, P. Downey, T. Peakman, J. Danesh, P. Elliott, J. Gallacher, J. Green, P. Matthews, J. Pell, T. Sprosen, and R. Collins. UK Biobank: Current status and what it means for epidemiology. Health Policy and Technology 2012;1:123-126.
2. Buckley, J. P., A. Hedge, T. Yates, R. J. Copeland, M. Loosemore, M. Hamer, G. Bradley, and D. W. Dunstan. The sedentary office: an expert statement on the growing case for change towards better health and productivity. Br. J. Sports Med. 2015;49:1357-1362.
3. Bureau of Labor and Statistics. American Time Use Survey 2014, 2015.
4. Ekelund U, Steene-Johannessen J, Brown WJ, Fagerland MW, Owen N, Powell KE, Bauman A, Lee IM, Lancet Physical Activity Series 2 Executive Committe, and Lancet Sedentary Behaviour Working Group. Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women. Lancet, 2016;388:1302-10.
5. Mekary, R. A., W. C. Willett, F. B. Hu, and E. L. Ding. Isotemporal substitution paradigm for physical activity epidemiology and weight change. Am. J. Epidemiol. 2009;170:519-527.
6. Scholes S and Mindell J. Health Survey for England 2012 – Volume 1 Chapter 2 Physical activity in adults. London: Health and Social Care Information Centre, 2013.
7. Tremblay, M. S., A. G. Leblanc, I. Janssen, M. E. Kho, A. Hicks, K. Murumets, R. C. Colley, and M. Duggan. Canadian sedentary behaviour guidelines for children and youth. Appl. Physiol Nutr. Metab 2011;36:59-64.
8. Wijndaele, K., S. Brage, H. Besson, K. Khaw, S. Sharp, R. Luben, N. Wareham, and U. Ekelund. Television viewing time independently predicts all-cause and cardiovascular mortality: the EPIC Norfolk Study. Int. J. Epidemiol. 2011;40:150-9.
9. Wijndaele, K., S. J. Sharp, N. J. Wareham, and S. Brage. Mortality Risk Reductions from Substituting Screen Time by Discretionary Activities. Med. Sci. Sports Exerc. 2017;49:1111-1119.