The Importance of Maintaining Muscle Function in Older Adults

The purpose of this study was to look at the relationship between muscle mass and muscular function and the risk of losing physical independence in later life >90+ years

Higher odds of losing physical independence in later life were observed in adults with low muscle functioning, regardless of their muscle mass status

Even though reducing skeletal muscle mass is a natural part of growing older, the loss of muscle quality and function appears to have more impact

Introduction

Muscle mass and function play an important role in sustaining physical independence and general health in later life. Muscle mass and function naturally diminish with age, which can have several detrimental effects on an individual, including reduced mobility, an increased risk of falls, and a loss of independence in carrying out everyday tasks. Understanding how muscle mass and function affect physical independence is critical for designing effective therapies and strategies to promote healthy aging and avoid or delay the emergence of physical dependence. The purpose of this study was to look at the independent and synergistic connections between muscle mass and muscular function and an increased risk of losing physical independence later in life. The researchers wanted to look at the relationship between these elements and how they can affect an individual’s capacity to maintain physical independence as they age. The information from this study can be used to make recommendations about the importance of maintaining muscle function in older adults, as muscle mass will surely decline with the aging process.

 

Methods

In this cross-sectional study, the researchers collected data from a large population of community-dwelling people in Portugal from the age of 65 years to evaluate the association between muscle mass, muscle function, and the risk of losing physical independence.

Measurements obtained included:

  • Weight and height to calculate the body mass index (BMI)
  • Skeletal muscle mass was estimated using an equation and adjusted by height squared to calculate the skeletal muscle index. Low muscle mass was defined as a score on the lower 20th percentile. In this sample, this cutoff was 9.1 kg/m2 for males and 6.5 kg/m2 for females.
  • Muscle function was estimated using the 30-second chair stand test. Low muscle function was defined as someone with a score in the 20th percentile for each sex and adjusted for their age and skeletal muscle index.
  • Physical independence was assessed using the 12-item Composite Physical Function scale self-report questionnaire. An age-adjusted scoring option was included to define whether someone had a high or low risk of losing physical independence at the age of 90 years and above. When someone was classified as moderate to high functioning based on the answers to the questionnaire, the risk of losing physical independence was low. Contrastingly, someone with low functioning based on the questionnaire, was categorized as having a high risk for future loss of physical independence. The details are provided in the picture below; referenced from Rikli et al., 2012
Maintaining muscle function in older adults 2
From: Rikli et al., Gerontologist. 2013

 

The subjects were tracked over time and their muscle mass and function were tested at regular intervals. The researchers also kept track of any changes in their physical independence, such as their capacity to carry out everyday tasks without assistance.

The study looked at the links between muscle mass, muscular function, and the risk of losing physical independence. They investigated how these characteristics, both individually and collectively, increased the risk of experiencing a reduction in physical independence.

 

Results

Almost 3500 people were included in the study. They were on average 75 years old and overweight (BMI of 28 kg/m2). There were almost double the number of females in this study.

Maintaining muscle function in older adults
From: Dos Santos et al., J Cachexia Sarcopenia Muscle (2017)

 

Based on the outcomes of the Composite Physical Function score, almost 30% of the people included in this cohort were classified as having a high risk of losing physical independence at 90+ years. Females in this cohort had a higher risk (34%) compared to males (22.5%).

The Composite Physical Function score was lower among those with low muscle function and low muscle mass and in those with low muscle function and normal muscle mass. These differences were statistically significant.

Maintaining muscle function in older adults 4
From: Dos Santos et al., J Cachexia Sarcopenia Muscle (2017)

 

The logistic regression analysis revealed that people with low muscle mass had increased odds of being at risk of losing physical independence in later life (OR = 1.65; 95% CI 1.27-2.31) compared to people with normal muscle mass. Low muscle functioning increased the odds almost sixfold (OR = 6.19; 95% CI 5.08-7.53).

Maintaining muscle function in older adults 3
From: Dos Santos et al., J Cachexia Sarcopenia Muscle (2017)

 

When muscle mass and muscle functioning were analyzed as synergists, the results revealed:

  • When those with low muscle mass but normal muscle functioning were compared to the reference group (with normal mass and function), the odds of losing physical independence were only slightly increased (OR = 1.46; 95% CI 1.09-1.97).
  • People with normal muscle mass and low muscle functioning had increased odds of losing physical independence (OR = 5.68; 95% CI 4.56-7.07)
  • The odds of losing physical independence in later life increased drastically when people had both low muscle mass and functioning (OR = 12.28; 95% CI 7.95-18.96)
Maintaining muscle function in older adults 5
From: Dos Santos et al., J Cachexia Sarcopenia Muscle (2017)

 

Questions and thoughts

Muscle function and muscle mass go hand in hand and the analysis was adapted to assess the synergistic roles of muscle mass and function. Low muscle mass itself is not a strong predictor of losing physical independence. People with low muscle mass (MM) had a 1.65 greater chance of being at risk of losing physical independence in later life, whereas people with low muscle function (MF) had a considerably larger odds ratio of 6.19. This does not mean that muscle mass is of less importance since the study discovered that persons with both low muscle mass and impaired muscle function had a 12.28 odds ratio for losing physical independence. This implies that having both sarcopenia criteria, low muscle mass and low muscular function raises the likelihood of losing physical independence later in life. Maintaining muscle function in older adults seems to be paramount.

Participants with low muscle mass were on average older than those with normal muscle mass. This is partly explainable due to the normal aging process where muscle mass decreases over the years. As such, when someone ages, they’ll likely lose muscle mass and this may explain why the groups were different in age characteristics—the same accounts for the lower BMI in older adults with lower muscle mass.

 

Talk nerdy to me

The analyses were adjusted for age, sex, education, medical history of chronic diseases, hypertension, elevated cholesterol or glycemia, current medication status, and BMI.

This study included a relevant and easy-to-assess method to assess muscle function with the 30-second chair test. It was furthermore found to be a valid indicator of functional muscle strength in older adults by the study of Alcazar et al., 2020 and has a good reproducibility.

Skeletal muscle mass was estimated using an equation. This way the costly and highly specialized investigations were not needed, although this may be a limitation since it may have less accurately measured muscle mass in this population. However, muscle function was of larger importance in this cohort, and the assessment of muscle functioning was based on a widely available test.

The study was of cross-sectional origin, meaning that the data was collected at one point in time and no follow-up of these individuals was included. The risks of losing physical independence were derived from the regression analysis and not from a follow-up of this cohort.

For all tests, the significance was set at p<0.05, hence there was no correction for multiple comparisons, which may be a limitation.

 

Take home messages

When someone performs the 30-second chair stand test and scores in the 20th profile based on his age, sex, and skeletal muscle index, they have a 6-fold increased risk of losing physical independence at 90 years of age, compared to someone with normal muscle functioning. This risk of losing physical independence rises 12-fold when it is combined with low muscle mass (<9.1 kg/m2 for males and <6.5 kg/m2 for females). Therefore, maintaining muscle function in older adults seems the most important factor in keeping physical independence in later life. Of course, you cannot have good muscle function without having decent muscle mass, but prevention of further decline of muscle functioning seems the go-to option, even in those with an already marked decline in muscle mass.

 

Reference

Dos Santos L, Cyrino ES, Antunes M, Santos DA, Sardinha LB. Sarcopenia and physical independence in older adults: the independent and synergic role of muscle mass and muscle function. J Cachexia Sarcopenia Muscle. 2017 Apr;8(2):245-250. doi: 10.1002/jcsm.12160. Epub 2016 Nov 8. PMID: 27897417; PMCID: PMC5377449. 

Additional reference

Rikli RE, Jones CJ. Development and validation of criterion-referenced clinically relevant fitness standards for maintaining physical independence in later years. Gerontologist. 2013 Apr;53(2):255-67. doi: 10.1093/geront/gns071. Epub 2012 May 20. PMID: 22613940. 

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