The authors have declared that no competing interests exist.
Conceived and designed the experiments: MH ES. Analyzed the data: MH. Wrote the paper: MH ES. Sourced the data: MH.
Sarcopenia is associated with loss of independence and ill-health in the elderly although the causes remain poorly understood. We examined the association between two screen-based leisure time sedentary activities (daily TV viewing time and internet use) and muscle strength.
We studied 6228 men and women (aged 64.9±9.1 yrs) from wave 4 (2008-09) of the English Longitudinal Study of Ageing, a prospective study of community dwelling older adults. Muscle strength was assessed by a hand grip test and the time required to complete five chair rises. TV viewing and internet usage were inversely associated with one another. Participants viewing TV ≥6hrs/d had lower grip strength (Men, B = −1.20 kg, 95% CI, −2.26, −0.14; Women, −0.75 kg, 95% CI, −1.48, −0.03) in comparison to <2hrs/d TV, after adjustment for age, physical activity, smoking, alcohol, chronic disease, disability, depressive symptoms, social status, and body mass index. In contrast, internet use was associated with higher grip strength (Men, B = 2.43 kg, 95% CI, 1.74, 3.12; Women, 0.76 kg, 95% CI, 0.32, 1.20). These associations persisted after mutual adjustment for both types of sedentary behaviour.
In older adults, the association between sedentary activities and physical function is context specific (TV viewing vs. computer use). Adverse effects of TV viewing might reflect the prolonged sedentary nature of this behavior.
Age related declines in muscle mass and strength, known as sarcopenia, are a risk factor for health and independence in the elderly. Measures of muscle strength have been associated with morbidity, functional independence and mortality in older populations
Prolonged sedentary activities, particularly watching TV, have been associated with a range of adverse health outcomes independently from physical activity
Participants gave full informed written consent to participate in the study and ethical approval was obtained from the London Multi-centre Research Ethics Committee.
The English Longitudinal Study of Ageing (ELSA) is an ongoing cohort study that contains a nationally representative sample of the English population living in households
Participants were asked to recall “How many hours of television do you watch on an ordinary day or evening, that is, Monday to Friday?” and “How many hours of television do you normally watch in total over the weekend, that is, Saturday and Sunday?” Average daily time spent watching TV was calculated as {(weekday TV time x 5) + (Weekend TV time)}/7. Daily TV time was categorized into four groups (<2hrs/d; 2 to <4 hrs/d; 4 to <6hrs/d; ≥6 hrs/d). In addition participants were asked if they used a computer for internet or email. We have described the ELSA physical activity measurements in detail previously
Physical strength measures included hand grip and a timed chair stand test. Hand grip strength (kg) of the dominant hand was assessed using a hand held dynamometer, with the average of three measures used in the analyses. The intra-class correlation of average measures was high (0.987, 95% CI, 0.987, 0.988). The chair stand test, a measure of lower body strength, assessed the time required to rise from a chair to a full standing position five times with arms folded across the chest, with slower times reflecting worse function. The test incorporated the use of respondent’s own armless, straight backed chair.
Demographic and health-related questions included cigarette smoking (current, previous or non-smoker), frequency of alcohol intake (daily, 5–6/wk, 3–4/wk, 1–2/wk, 1–2/month, once every couple of months, 1–2/year, never) and self-reported chronic illness. Depressive symptoms were assessed using the 8-item Centre of Epidemiological Studies Depression (CES-D) scale, highly validated for use in older adults
In order to examine associations between sedentary behaviors and muscle strength we employed general linear models. The dependent variables were normally distributed. We calculated coefficients and 95% CIs for hand grip strength (kg) and chair stand time (seconds) with reference to the TV viewing category and a binary internet use variable (No/Yes). These analyses were performed separately among men and women due to the well documented differences in muscle strength between sexes
From the initial 8643 participants that attended wave 4, a total of 8343 participants provided valid data from physical performance tests. Participants that refused or were unable to provide these measures tended to be slightly older than those who consented and had valid measures (70.8±11 vs 68.2±11.3 yrs). A further 2115 participants were excluded due to missing data leaving a final analytic sample of 2845 men and 3383 women (aged 64.9±9.1 yrs). Participants excluded tended to be older (68.2±11.3 yrs, p<0.001), have lower BMI (23.8±11.9 vs. 28.2±5.2 kg/m2, p = 0.001), although more depressive symptoms (3.3±1.5 vs. 2.9±1.3, p = 0.001), and a higher prevalence of chronic illness (63.1 vs. 51.4%, p<0.001).
<2 hrs/d (n = 655) | 2<4 hrs/d (n = 2183) | 4<6 hrs/d (n = 1676) | ≥ 6 hrs/d (n = 1715) | |
Age (mean [SD] yrs) | 63.8±9.2 | 64.4 ±9.1 | 65.6±9.1 | 65.2±9.0 |
Men | 53.1 | 48.5 | 43.1 | 41.7 |
Current smokers | 6.0 | 10.2 | 11.7 | 18.0 |
Physically active |
90.0 | 86.6 | 80.6 | 74.9 |
Regular alcohol intake |
73.8 | 69.4 | 59.2 | 57.2 |
Lowest social status |
17.7 | 26.2 | 39.1 | 53.8 |
Chronic illness | 44.8 | 47.5 | 53.8 | 56.3 |
Disability | 16.6 | 16.6 | 21.9 | 30.4 |
Obese (BMI ≥30 kg/m2) | 17.6 | 26.2 | 34.3 | 38.5 |
Users of internet | 76.6 | 69.7 | 54.5 | 43.3 |
Data presented as percentages unless otherwise stated.
defined as moderate or vigorous activity at least once per week.
defined as alcohol intake at least once per week.
Defined as routine/manual occupations.
As expected, men recorded higher grip strength (38.7±9.5 vs. 22.9±6.4 kg, p<0.001) and a faster time to complete 5 chair rises (10.9±3.7 vs. 11.4±4.1 sec, p<0.001) compared with women. Other variables that were consistently and independently associated with the physical performance tests included physical activity, disability, chronic illness, depressive symptoms and social occupational class (see
Sedentary exposure | N | Age adjustedB |
MultivariateB |
Age adjustedB |
MultivariateB |
<2 hrs/d | 349 | Reference | Reference | Reference | Reference |
2<4 hrs/d | 1055 | −0.54 (−1.54, 0.46) | −0.58 (−1.55, 0.39) | −0.04 (−0.48, 0.39) | −0.20 (−0.62, 0.22) |
4<6 hrs/d | 724 | −0.73 (−1.79, 0.32) | −0.27 (−1.30, 0.77) | 0.24 (−0.22, 0.70) | −0.25 (−0.70, 0.20) |
≥6 hrs/d | 717 | −2.47 (−3.52, −1.41) | −1.20 (−2.26, −0.14) | 0.65 (0.18, 1.12) | −0.08 (−0.54, 0.39) |
<0.001 | 0.076 | 0.001 | 0.62 | ||
No | 1007 | Reference | Reference | Reference | Reference |
Yes | 1838 | 3.25 (2.58, 3.92) | 2.43 (1.74, 3.12) | −0.84 (−1.14, −0.54) | −0.44 (−0.75, −0.13) |
<0.001 | <0.001 | <0.001 | 0.005 |
General linear model coefficients; coefficients indicate mean differences (in muscle strength markers) between each screen time group and the reference category.
Sedentary exposure | N | Age adjustedB |
MultivariateB |
Age adjustedB |
MultivariateB |
<2 hrs/d | 306 | Reference | Reference | Reference | Reference |
2<4 hrs/d | 1127 | −0.47 (−1.19, 0.25) | −0.41 (−1.10, 0.29) | −0.04 (−0.46, 0.54) | −0.14 (−0.64, 0.34) |
4<6 hrs/d | 952 | −1.07 (−1.81, −0.34) | −0.65 (−1.37, 0.07) | 0.53 (0.02, 1.04) | −0.04 (−0.54, 0.45) |
≥6 hrs/d | 998 | −1.54 (−2.26, −0.81) | −0.75 (−1.48, −0.03) | 0.71 (0.20, 1.22) | −0.04 (−0.54, 0.47) |
<0.001 | 0.173 | <0.001 | 0.90 | ||
No | 1541 | Reference | Reference | Reference | Reference |
Yes | 1842 | 1.55 (1.12, 1.98) | 0.76 (0.32, 1.20) | −0.79 (−1.10, −0.49) | −0.17 (−0.48, 0.13) |
<0.001 | 0.001 | <0.001 | 0.268 |
General linear model coefficients; coefficients indicate mean differences (in muscle strength markers) between each screen time group and the reference category.
In sensitivity analyses, missing values were imputed (SPSS multiple imputation procedure) based on maximum likelihood estimates although a similar pattern of results was obtained. For example, the association between TV time (modelled as a continuous variable) and hand grip strength using imputed data was similar to the original results (Men, fully adjusted B = −0.12, 95% CI, −0.14, −0.09; Women, B = −0.04, 95% CI, −0.06, −0.03).
The aim of this study was to examine associations between two key leisure time screen-based sedentary activities (daily TV viewing time and internet use) and common tests of physical performance in a sample of community dwelling older adults. Several previous studies have observed associations between physical activity and muscle strength tests
These data may be interpreted in several ways. Firstly, given that these two sedentary behaviors were strongly socially patterned but in opposite directions suggest that the results might merely reflect residual confounding effects of social status that cannot be fully captured by the occupational social class measure that we adjusted our analyses for. We have repeatedly shown that combining different socioeconomic indicators can considerably improve the prediction of leisure-time screen-based sedentary behaviour
The associations we observed for screen-based sedentary behaviour were largely confined to hand grip strength. This is perhaps not surprising because chair rising is a far more complex test that not only involves strength but also neuromuscular control. Hand grip is a simple isometric test of upper body muscle strength. Previous data from middle aged British adults suggested that physical activity had stronger protective effects on handgrip strength in men than in women
Our study has some limitations. We did not assess all types of sedentary behaviors and therefore our results cannot be generalized to total sedentary time. Nevertheless, TV viewing is arguably the most prevalent form of sedentary activity in the elderly
In conclusion, we observed associations between two key screen-based sedentary behaviors and muscle strength independently of physical activity, although the relationships appeared to be context specific. Our results suggest that TV viewing carries its own health risks in older age over and above the sitting it entails.
Unadjusted mean grip strength in relation to TV viewing.
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Scatter plot of TV viewing against grip strength (upper panel) and chair rises time (lower panel).
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The association between covariables and muscle strength in men (N = 2845).
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The association between covariables and muscle strength in women (N = 3383).
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