Stronger evidence links sedentary behavior and frailty in old age

by | Apr 19, 2024

Data gathered from hundreds of thousands of individuals finds strong link between sedentary behavior and becoming frail, simple changes can help.
An elderly woman walking through a park.

For the first time, using advanced statistical methods, researchers have linked frailty in old age with our growing sedentary lifestyles. “For the public, our findings underscore the importance of adopting an active lifestyle, particularly in reducing sedentary behavior, to prevent frailty and related health issues [in later life],” explained Yong Zeng, professor at the Second Affiliated Hospital of Kunming Medical University, China.

This first-of-its-kind statistical study investigated how modifiable sedentary behaviors, such as prolonged time spent watching television, increases the risk of becoming weak or frail in our old age. We all want to live longer, but as we age, becoming frail seems inevitable. However, Zeng and his team’s recent research published in Advanced Biology suggests there are lifestyle changes we can make that can help prevent this.

“Even simple daily activities, such as standing and walking at regular intervals, could have a positive impact on the health and quality of life of older adults,” he said.

A weak link

But what does it mean to be frail? Zeng describes it as a weakening of multiple body systems related to age, but other risk factors, such as socioeconomic status, nutrition, smoking, and possible illness, likely also affect our ability to live independently as we get older.

Prior to Zeng and his team’s work, most evidence for these associations came from observational studies where scientists observe and collect data to explore relationships between factors without controlling any variables. While useful to gain insights into different phenomena, observational studies can’t establish causation, only associations or correlations between variables.

Previous observational studies revealed such a link between sedentary behavior and frailty. However, they cannot prove causation because of the aforementioned additional underlying influences, also known as confounding factors, which are difficult to control in statistical analyses.

A superior statistical approach was therefore needed to interrogate this apparent link and strengthen evidence that sedentary behavior is indeed a cause of frailty — and what can be done about it.

Linking genetics and sedentary behavior

To overcome the limitations of observational studies, an advanced statistical method known as mendelian randomization can be used to differentiate between associations present by chance and those occurring because one variable is causing the other. This approach looks at genetic differences between people and how different factors lead to specific health outcomes as a result.

“You can think of it as a natural experiment,” explained Zeng. “Since people cannot choose their genetic variations, these variations are unrelated to their lifestyle choices, yet may influence these choices.” This makes the evidence stronger compared to an observational study alone.”

Using this method and other quality control measures, the researchers analyzed genetic information pooled from three large studies gathered from hundreds of thousands of individuals, one of which had surveyed participants about their sedentary behaviors, which included watching TV, driving, and computer use.

The scientists looked for differences in the DNA sequences of individuals — known as single-nucleotide polymorphisms — and then checked to see if such variations associated with either sedentary behavioral traits, frailty, or both.  

“If we find a genetic variation that is associated with a higher tendency for sedentary behavior, and this variation is also associated with an increased risk of frailty, then we can be more confident in saying that sedentary behavior is one of the causes of frailty,” said Zeng.

While this statistical approach strengthens the evidence for causation and is a step forward, more data is needed to provide definitive proof — though the link provided by the current study is quite strong. Zeng also explained that long-term clinical studies are needed to define the effect of reducing sedentary time and increasing physical behavior.

Lifestyle modifications that could significantly reduce risk

Interestingly, the team also found that the type of sedentary behavior mattered when it came to determining risk of frailty. Watching television but not driving or using a computer statistically heightens this risk by approximately 40%. The reasons remain unknown, but Zeng speculates that different biological mechanisms may be at play.

“Watching television typically involves longer periods of inactivity, while using a computer or driving may involve more frequent physical activity or shifts in attention, which could have varying biological impacts on the body,” he said. This finding could help focus efforts to develop the best type of interventions needed going forward.

“By altering controllable lifestyle factors, such as reducing sedentary time, the risk of frailty can be significantly lowered […] even though genetic factors may have some influence on an individual’s susceptibility to frailty, active lifestyle changes can still mitigate or delay [its] development,” Zeng explained.

But it is not only physical exercise that can slow down this decline; studies have found that increasing levels of social engagement and even the level of availability of nearby green spaces can help, illustrating the multi-faceted nature of this problem.

The researchers believe that the evidence from their study will further inform public health guidelines and strategies to promote behavioral changes. With mounting evidence, the notion that frailty can be prevented (or at least delayed) is gaining traction worldwide.

“The World Health Organization (WHO) and public health departments of many countries also actively promote enhanced activity and healthy lifestyles to prevent frailty,” said Zeng. “These initiatives typically aim to improve the health of the elderly but are increasingly focusing on middle-aged individuals to prevent frailty in later life.”

Reference: Yu, L, et al., Modifiable Lifestyle, Sedentary Behaviors and the Risk of Frailty: A Univariate and Multivariate Mendelian Randomization Study, Advanced Biology (2024). DOI: 10.1002/adbi.202400052

Feature image credit: William Olivieri on Unsplash

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