Being a couch potato is even worse than we thought

Most of us probably realise that spending hours on end sitting on the sofa isn’t particularly good for us. We could perhaps also guess that older people tend to spend a significant proportion of their time engaged in sedentary behaviour.

Sedentary behaviour is defined as a cluster of behaviours involving non-exercising sitting or reclining – watching TV, for example. Analysis of participants aged 60 and over in the USA National Health and Nutrition Examination Survey showed more than 60% of their waking time was spent sedentary. Other studies report even higher proportions of waking time spent in sedentary pursuits (up to 75% in community-dwelling older adults and 90% in care home residents).

A recent systematic review found that almost 60% of older people reported sitting for more than four hours per day, while 65% sat in front of a screen for more than three hours daily and more than 55% watched more than two hours of TV per day. Clearly for many older people, a substantial proportion of the day is spent sitting.

So what are the effects of sedentary behavior on older people’s health? Until relatively recently, sedentary behaviour was classed alongside the rest of the ‘lower end’ of the physical activity spectrum. However, there is accumulating evidence showing that sedentary behaviour on its own – rather than simply overall low physical activity – is a major modifiable risk factor for chronic diseases such as cardiovascular disease, cancer and type 2 diabetes. It is also a predictor of cardiovascular and all-cause mortality, independentof the total amount of physical activity a person does.

This isn’t good news for us ‘weekend warriors’ who exercise hard on Saturday and Sunday but spend the rest of our week sitting in front of TV screens and computers, or in cars and buses.

The current UK physical activity guidelines state that older people should not only be more active but that they should also be less inactive. The guidelines tell us that ‘while there is sufficient evidence to support a recommendation to reduce sedentary behaviour in older adults, it is not currently possible to suggest a specific time limit’.

We need to be able to characterise sitting time in older adults in terms of the effects on both their bodies (for example, muscle strength and power) and minds (for example, thinking and memory).  We also need to identify the main effects reported by older people following periods of sitting, as well as finding effective and acceptable ways of interrupting sitting time that could be incorporated into a daily routine.

In this way, we may be able to generate specific advice for older people, but at the moment the research simply doesn’t exist. Addressing these knowledge gaps is a research priority – being a couch potato is even worse for us than we thought.

Dr Carolyn Greig, Senior Lecturer in Nutrition and Ageing, University of Birmingham