Published in a recent Bio Med Central journal article,[i] researchers at the University of Glasgow have identified that an increase in discretionary viewing of television and computer screens almost doubles the negative effects on human health as low fitness levels.
The rationale for this study was that discretionary screen time was thought to be a contributor to sedentary behaviour, which is positively correlated with mortality and cardiovascular disease.
390,089 participants were selected from the UK Biobank and their behaviours were analysed. Researchers were only interested in the amount of time spent watching screens during the test subjects’ leisure time. Other factors, such as physical activity, grip strength, BMI, smoking, diet and socio-economic status, were also taken into account.
The test results emphasise that sedentary behaviour, generally, is detrimental to human health. The incidence of ‘all-cause mortality’, cancer and cardiovascular disease, caused by screen time, was almost double the attributable risk presented by low fitness levels.
Lead author of the study, Professor Jason Gill, stated:
‘Our study shows that the risks associated with sedentary behaviour may not be the same for everyone, with the association between leisure time screen use and adverse health outcomes being strongest in those with low levels of physical activity, fitness or strength. This has potential implications for public health guidance as, if the findings are causal, these data suggest that specifically targeting those with low fitness and strength to reduce their sedentary behaviour may be an effective approach’.[ii]
Somewhat inevitably, Professor Gill implies that risk factors (screen viewing and low fitness) are not mutually exclusive, with the most adverse health effects observed in participants who spent more time watching screens and had low levels of physical activity.
As a result, study author, Dr Carlos Celis, shared in Professor Gill’s advisory comments that ‘people with the lowest levels of strength, fitness and physical activity could potentially gain the greatest benefit from health promotion interventions aimed at reducing sedentary behaviours’.
He went on to say that ‘grip strength is a quick, simple and cheap to measure, so could easily be implemented as a screening tool in a variety of settings’.
[i] Carlos A. Celis-Morales, et al., Associations of discretionary screen time with mortality, cardiovascular disease and cancer are attenuated by strength, fitness and physical activity: findings from the UK Biobank study, BMC Medicine, 201816:77, <https://doi.org/10.1186/s12916-018-1063-1> accessed 4 June 2018.