Ellen Vandyck
Research Manager
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.
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:
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.
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.
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.
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).
When muscle mass and muscle functioning were analyzed as synergists, the results revealed:
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.
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.
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.
Additional reference
Receive 6 High-Resolution Posters summarising important topics in sports recovery to display in your clinic/gym.