BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK.
Institute of Health and Wellbeing, University of Glasgow, Glasgow, G12 8RZ, UK.
BMC Med. 2018 May 24;16(1):77. doi: 10.1186/s12916-018-1063-1.
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 (all-cause mortality hazard ratio per 2-h increase in screen time (1.31 [95% confidence interval: 1.22-1.43], p < 0.0001; CVD 1.21 [1.13-1.30], p = 0.0001; cancer incidence 1.14 [1.10-1.19], p < 0.0001) and weakest amongst those in the highest grip-strength tertile (all-cause mortality 1.04 [0.95-1.14], p = 0.198; CVD 1.05 [0.99-1.11], p = 0.070; cancer 0.98 [0.93-1.05], p = 0.771). Similar trends were found for fitness (lowest fitness tertile: all-cause mortality 1.23 [1.13-1.34], p = 0.002 and CVD 1.10 [1.02-1.22], p = 0.010; highest fitness tertile: all-cause mortality 1.12 [0.96-1.28], p = 0.848 and CVD 1.01 [0.96-1.07], 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.
闲暇时间看电视或电脑屏幕的随意屏幕时间（discretionary screen time）是总久坐行为的一个重要贡献者，与死亡率和心血管疾病（CVD）风险增加有关。本研究的目的是确定屏幕时间与心血管疾病和全因死亡率的关联是否受到心肺功能适应性、握力或体力活动水平的影响。
总共纳入了来自英国生物银行的 390089 名参与者（54%为女性）。全因死亡率、心血管疾病和癌症发病率和死亡率是主要结局。所有屏幕时间（电视观看时间、个人电脑屏幕时间和总屏幕时间（电视+个人电脑时间））是暴露变量。握力、适应性和体力活动被视为潜在的效应修饰剂。
在中位随访 5.0 年（四分位距 4.3 至 5.7；从基线的前 2 年排除在 landmark 分析之外）期间，共有 7420 名参与者死亡，发生了 22210 例心血管疾病事件。所有随意屏幕时间暴露都与所有健康结果显著相关。在握力最低三分位的参与者中，总随意屏幕时间与全因死亡率和心血管疾病及癌症发病的关联最强（每增加 2 小时屏幕时间，全因死亡率的危险比（1.31[95%置信区间：1.22-1.43]，p<0.0001；心血管疾病 1.21[1.13-1.30]，p=0.0001；癌症发病 1.14[1.10-1.19]，p<0.0001），而在握力最高三分位的参与者中最弱（全因死亡率 1.04[0.95-1.14]，p=0.198；心血管疾病 1.05[0.99-1.11]，p=0.070；癌症 0.98[0.93-1.05]，p=0.771）。在适应性方面也发现了类似的趋势（适应性最低三分位：全因死亡率 1.23[1.13-1.34]，p=0.002 和心血管疾病 1.10[1.02-1.22]，p=0.010；适应性最高三分位：全因死亡率 1.12[0.96-1.28]，p=0.848 和心血管疾病 1.01[0.96-1.07]，p=0.570）。对于体力活动与全因死亡率和癌症发病率也有类似的发现。
在握力、适应性和体力活动水平较低的人群中，随意屏幕时间与不良健康结果之间的关联最强，而在握力、适应性和体力活动水平最高的人群中，这些关联明显减弱。因此，如果这些关联是因果关系的，那么通过健康促进干预措施减少随意屏幕时间可能会使那些握力、适应性和体力活动水平较低的人获得最大的健康益处。
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