In a study recently published in JAMA Network Open, researchers investigated the independent associations of sedentary behavior and light physical activity (LPA) with healthy aging. Previous studies have shown that replacing sedentary behavior with improved sleep quality and moderate-to-vigorous physical activity (MVPA) may increase an individual's chances of healthy aging (living to age 70 without chronic disease, psychiatric illness, decline in physical function, or subjective memory impairment). However, the impact of LPA on healthy aging has not previously been systematically evaluated.
Study: Sedentary behavior, light exercise, and healthy aging. Image credit: Studio Romantic / Shutterstock
This study, which followed a large cohort of women (N = 45,176) over a long period of time (over 20 years), found that every 2 hours of daily TV viewing (sedentary behavior) reduced the odds of healthy aging by 12%, while replacing this behavior with 2 hours of LPA increased this odds by 6% across all four domains of healthy aging. Notably, for people who slept less than 7 hours daily, replacing just 1 hour of TV viewing with sleep or MVPA similarly improved the odds of a long and healthy older age.
Living longer and better – is global ageing a boon or a cause for concern?
Increasing human lifespan is one of the highlights of modern medicine. Advances in medical research and greater public access have increased global life expectancy from 45 years in 1850 to almost 80 years today. In the past 60 years alone, reports estimate that medical advances have increased global life expectancy by an unprecedented 23 years. While these figures are laudable and noteworthy, they also unexpectedly raise new concerns. More than 8.5% of the world's population is aged 65 or older, and this percentage is expected to rise to 20% by 2050.
Unfortunately, because evolutionary processes, especially natural selection, proceed over much longer timescales, older age (beyond reproductive age) is often accompanied by adverse health outcomes, including chronic diseases, mental illness, cognitive decline, and physical disability. Studies estimate that only 10-35% of adults aged 69 years and older achieve “healthy aging,” an ideal state free of age-related health concerns. There is therefore an urgent need to identify approaches to achieve this ideal state, with modifiable health behaviors (sleep duration and quality, physical activity, and sedentary behavior) being the primary focus of ongoing research.
“24-h behaviors can be divided into sleep behavior, sedentary behavior (SB), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA), which are important modifiable factors for health. Among them, MVPA is associated with an increased probability of healthy aging, and sleep duration has been shown to have an inverted U-shaped association with healthy aging, with seven hours of sleep per day being associated with the highest probability of healthy aging.”
Isochronal Modeling MVPA has been shown to improve health outcomes with age. On the other hand, sedentary behavior has been observed to have the opposite effect. Unfortunately, in modern societies, MVPA accounts for only 4% of adults' waking time on average, whereas sedentary behavior accounts for more than 60%. The transition from sedentary behavior to LPA is easier than a direct switch from the latter to MVPA, especially for older adults. Unfortunately, the benefits of LPA in healthy aging have not been tested so far.
About the Research
In this longitudinal cohort study, the researchers aim to evaluate the independent associations of LPA and sedentary behavior with healthy aging and to determine the benefits of replacing sedentary behavior with LPA, sleep, or MVPA in an ageing population. The study complies with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guidelines. The study cohort was derived from the Nurses' Health Study (NHS) and included participants aged 50 years and older with no history of major chronic diseases at baseline (1992). The follow-up period was 20 years, with the final assessment taking place from January to March 2022.
The primary outcome of interest was survival to age 70 years without developing health-related concerns, specifically across four health domains: chronic disease, cognitive impairment, physical functional decline, and mental disorders.
“We included three SBs, two LPAs, MVPA and sleep time. Of these, we considered sitting and watching TV time as the main exposure because, among the various surrogates for SB, TV watching time was most strongly associated with adverse health outcomes.”
Data collection consisted of medical, anthropometric and socio-demographic records from NHS databases. A pre-validated health questionnaire was used to record the duration and intensity of participants' physical activity, sleep and sedentary behaviour (collectively 'exposures'). Equal-time substitution models were used to compare measured exposures with subsequent outcomes, adjusting models for age, ethnicity, education, marital status, family medical conditions and known health risk factors (e.g. smoking).
Findings and Conclusions
After reviewing study inclusion requirements, 45,176 participants were included in the analysis (mean age = 59.2 years), of which 3,873 (8.6%) achieved healthy aging. Findings showed that sedentary behaviors, particularly time spent sitting and watching TV, significantly worsened the odds of healthy aging by an average of 12% for every 2-hour increase in time spent in that activity. In contrast, LPA was associated with a 6% increase in the odds of healthy aging for every 2-hour increase in that behavior.
“Participants who watched more TV were more likely to be older, less educated, smoke more, drink more alcohol, have higher blood pressure and cholesterol, have a higher BMI, have a higher calorie intake, and have a lower diet quality than those who watched less TV.”
Substituting some form of physical activity for television viewing was observed to reverse the negative trends of television viewing on healthy aging, although the magnitude of the observed effect was dependent on the intensity of the physical activity undertaken. Notably, substituting sleep for television viewing had a similar effect in people who slept less than seven hours per day.
These findings complement previous research calling for population-wide increases in physical activity and decreases in sedentary behavior (with prolonged television viewing observed to be the worst). Given that LPA is easier to achieve than MVPA for physically inactive individuals (especially those aged 50 years and older), this study may provide a basis for future interventions targeting optimal health in older age.
