A new study from the University of Glasgow has found a strong association between discretionary screen time, that is electing to spend leisure time on screens, and adverse health outcomes, such as mortality and cardiovascular disease. This is particularly true of those with low fitness, low muscle strength or physical activity levels (via University of Glasgow).
The researchers analysed the behaviour of almost 400,000 people and discovered that the association between a high level of discretionary screen time and unfavourable health outcomes, was almost twice as strong in those with low fitness levels or low grip strength. More screen time was associated with an increased risk of all-cause mortality, as well as a higher risk of both heart disease and cancer.
Individuals who viewed screens for five or more hours each day (the highest screen category) had a higher prevalence of current smoking, obesity and comorbidities, including diabetes and hypertension as well as higher prevalence of being on medication for hypertension and higher cholesterol, when compared individuals who used screens during leisure time for fewer than two hours a day (the lowest screen-time group). They also had a higher BMI, waist circumference and percentage body fat, consumed more processed meat and less fruit and vegetables, as well as lower levels of physical activity, fitness and grip strength in comparison to those in the lowest screen-time group. While the researchers observed similar patterns when participants were stratified by TV-viewing categories, this was not the case for PC screen-time categories.
Source: Celis-Morales, C. A., et al. (2018)
University of Glasgow Too much screen time associated with heart disease and cancer
The paper has been published in the BMC
Discretionary screen time (time spent viewing a television or computer screen during leisure time) is an important contributor to total sedentary behaviour, which is associated with increased risk of mortality and cardiovascular disease (CVD). The aim of this study was to determine whether the associations of screen time with cardiovascular disease and all-cause mortality were modified by levels of cardiorespiratory fitness, grip strength or physical activity.
In total, 390,089 participants (54% women) from the UK Biobank were included in this study. All-cause mortality, CVD and cancer incidence and mortality were the main outcomes. Discretionary television (TV) viewing, personal computer (PC) screen time and overall screen time (TV + PC time) were the exposure variables. Grip strength, fitness and physical activity were treated as potential effect modifiers.
Altogether, 7420 participants died, and there were 22,210 CVD events, over a median of 5.0 years follow-up (interquartile range 4.3 to 5.7; after exclusion of the first 2 years from baseline in the landmark analysis). All discretionary screen-time exposures were significantly associated with all health outcomes. The associations of overall discretionary screen time with all-cause mortality and incidence of CVD and cancer were strongest amongst participants in the lowest tertile for grip strength and weakest amongst those in the highest grip-strength tertile (all-cause mortality 1.04, p = 0.198; CVD 1.05, p = 0.070; cancer 0.98, p = 0.771). Similar trends were found for fitness (lowest fitness tertile: all-cause mortality 1.23, p = 0.002 and CVD 1.10, p = 0.010; highest fitness tertile: all-cause mortality 1.12, p = 0.570). Similar findings were found for physical activity for all-cause mortality and cancer incidence.
The associations between discretionary screen time and adverse health outcomes were strongest in those with low grip strength, fitness and physical activity and markedly attenuated in those with the highest levels of grip strength, fitness and physical activity. Thus, if these associations are causal, the greatest benefits from health promotion interventions to reduce discretionary screen time may be seen in those with low levels of strength, fitness and physical activity.
Celis-Morales, C. A., et al|2018| 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 | https://doi.org/10.1186/s12916-018-1063-1
The article is available to download from BMC Medicine
In the media:
BBC High levels of screen time linked to cancer and heart disease