Those who may be tempted to binge watch the latest episodes of “Game of Thrones” may want to reconsider: A new study suggests time spent watching television is significantly related to subsequent risk for limited mobility among older adults.
In a longitudinal, prospective study involving more than 130,000 people, there was no significant association between sedentary behavior and the risk of walking disability among participants who exercised at least 7 hours a week, lead author Loretta DiPietro, PhD, MPH, and colleagues report in an article published online August 30 in the Journal of Gerontology: Series A. However, time watching television was associated with a dose-dependent increase in risk, regardless of the level of overall physical activity.
“TV viewing is a very potent risk factor for disability in older age,” Dr DiPietro, chair of the Department of Exercise and Nutrition Sciences at the Milken Institute School of Public Health, George Washington University, Washington, DC, said in a press release about the study. “Sitting and watching TV for long periods (especially in the evening) has got to be one of the most dangerous things that older people can do because they are much more susceptible to the damages of physical inactivity.”
The study is one of the first to address the joint associations between sitting time and physical activity with mobility disability: having difficulty walking or being unable to walk at all.
A Prospective, Longitudinal Analysis
The authors analyzed data from the National Institutes of Health–American Association of Retired Persons Diet and Health Study, which began in 1995 to 1996. The study consisted of 566,398 participants aged 50 to 71 years at baseline who answered a questionnaire about their medical history, diet, physical activity, and hours of active and sedentary time. Sedentary behavior was divided into total time engaged in activities such as sitting, napping, and working at the computer, as well as watching television, and just time spent watching television. The questionnaire also asked about hours per week spent in light-intensity activities such as housework or walking, and in activities of moderate to vigorous intensity, such as brisk walking, jogging, or yard work.
A follow-up questionnaire, distributed in 2004 to 2006, assessed mobility status through questions about normal walking pace, ranging from unable to walk or “easy” (less than 2 mph) through “very brisk” (4 mph or more). Mobility disability was defined as unable to walk or an “easy” normal pace.
Only people who completed both questionnaires, were free of chronic illnesses such as cancer or heart disease at baseline, and who had reported their health status as fair or better at baseline were included in the current analysis study. A total of 134,269 participants fit these eligibility criteria.
The cohort included 57,977 women (43.18%) and had an average age at baseline of 61.2 ± 5.3 years. Mean follow-up was 8.6 ± 0.42 years. Of the 38,798 (28.9%) participants reporting a mobility disability at follow-up, 58.00% were women (P < .001). Compared with no disability, mobility disability was associated with lower educational status, poorer health at baseline and follow-up, more smoking, and higher body mass index (P < .001 for all comparisons).
Participants with some mobility disability at follow-up had reported fewer hours per week of both light and moderate to vigorous activity at baseline than their peers. Similarly, hours per day spent watching television at baseline were significantly associated with limited mobility at follow-up (P < .001 for both comparisons.)
On logistic regression analysis, which adjusted for activity level as well as other variables such as race, educational level, and smoking status, sedentary behavior had an “almost negligible” relationship with mobility disability, the authors write.
Television watching showed a different pattern. Compared with 0 to 2 hours a day of television, 3 to 4 hours a day was associated with a 25% increase in risk for mobility disability (odds ratio [OR], 1.25; 95% confidence interval [CI], 1.215 – 1.293). With 5 hours or more of television, risk was increased by 65% (OR, 1.65; 95% CI, 1.587 – 1.713; P < .001 for both comparisons).
Activity level had an inverse effect on the risk for disability, independent of sitting time, television time, or other independent variables. For example, when analyzed in conjunction with sitting time, 4 to 7 hours per week of light activity was associated with a 20% decrease in the risk for disability (OR, 0.80; 95% CI, 0.766 – 0.839; P < .001). In a model using television time as the sole form of sedentary behavior, this level of activity again was associated with a 20% decrease in risk (OR, 0.80; 95% CI, 0.759 – 0.831; P < .001).
Similarly, more than 7 hours per week of moderate to vigorous activity was associated with a 57% decrease in disability risk (OR, 0.43; 95% CI, 0.411 – 0.449) in the first model and a 56% decrease in the second (OR, 0.44; 95% CI, 0.418 – 0.456; P < .001 for both comparisons).
Among people who spent the most time sitting (≥7 hours per day) and the least time in physical activity (≤3 hours a week), the odds of mobility disability were more than doubled (OR, 2.17; 95% CI, 2.03 – 2.32) compared with the least sedentary, most active participants. For people who engaged in the same degree of sedentary behavior but were active 4 to 7 hours a week, the OR was 1.34 (95% CI, 1.25 – 1.43), and “those reporting the highest level of sitting but who were most physically active (>7 h/wk) had excess odds of 11% (OR=1.11; 95% CI=1.02, 1.20),” the authors explain.
When they repeated these analyses using television time, “the results were even stronger,” they add. For example, among people who were active 4 to 7 hours/week, those who watched television for 5 or more hours a day had a 94% increase in the risk for disability (OR, 1.94; 95% CI , 1.82 – 2.08), which was close to that of participants who watched the least television, but who were also the least active (OR, 1.83; 95% CI, 1.73 – 1.94). Overall, the authors observed that more television time “was significantly related to increased disability within all levels of physical activity.”
The structured nature of television viewing may provide a more accurate estimate of sedentary time, which could account for its seemingly pernicious effect, the authors suggest. “Alternatively, people may break up their sitting time more frequently during the day compared with when watching TV in the evening.”
A third possibility is that heavy television watching plus low levels of physical activity may signal an underlying chronic illness; “however, we controlled for self-reported health status at follow-up and still observed excess mobility disability.”
Recommendations for healthy aging should include reducing sedentary time as well as increasing physical activity, they conclude.
Modern life “often includes 14 hours of sitting per day,” Dr DiPietro said in the press release. “Our findings suggest that older people who want to remain fit must ramp up their daily physical activity and reduce the amount of time they spend sitting.”
The authors have disclosed no relevant financial relationships.
J Gerontol A Biol Sci Med Sci. Published online August 30, 2017. Full text
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