Large and diverse cohort studies have shown that muscle strength, particularly grip strength, may indicate survival probability in older women, regardless of physical activity, sedentary time, or measured fitness level.
study: Muscle strength and mortality in women aged 63 to 99 years. Image credit: Chay_Tee/Shutterstock.com
In recent research, JAMA Network open We investigated whether muscle strength was associated with mortality in older women, while controlling for aerobic exercise, sedentary time, and fitness level.
The importance of muscle strength in aging
Current public health guidelines recommend skeletal muscle strengthening exercises at least twice a week to optimize whole-body physiology and maintain musculoskeletal integrity. Epidemiological evidence in middle-aged and older populations consistently shows that increased muscle strength is inversely associated with all-cause mortality risk.
Engagement in resistance training methods is associated with reduced risk of all-cause mortality, and progressive improvements in grip strength show an additional protective effect. Nevertheless, this association is likely to be modified by factors such as objectively measured aerobic physical activity and sedentary behavior.
Self-reported assessments of physical activity have limited accuracy in quantifying total daily physical activity and sedentary time, especially in older female cohorts. Although cardiorespiratory fitness represents a strong independent predictor of mortality, it is rarely incorporated as a confounding variable in analyzes of muscle strength outcomes. In this study, fitness was assessed using 2.5-meter walk time at a normal pace as a surrogate measure, rather than direct cardiorespiratory testing such as VO₂max assessment.
Aging is characterized by an increase in systemic functions. inflammationwhich contributes to reduced skeletal muscle contractility and mitochondrial dysfunction, thereby accelerating muscle weakness. Therefore, muscle strength maintenance is critical to maintain functional autonomy, reduce hospitalization rates, and improve overall quality of life in the elderly population.
Evaluation of the relationship between muscle strength and mortality in elderly women
This analysis included women aged 63 to 99 years from the Objective Physical Activity and Cardiovascular Health in Older Women (OPACH) study, a subsidiary study of the Women’s Health Initiative (WHI). The final analysis cohort consisted of 5,472 outpatient women who completed a physical performance test and a 7-day hip accelerometer wear. From 2012 to 2014, 7,875 WHI participants underwent at-home tests including blood draws, physical measurements, blood pressure, grip strength, and physical performance assessments.
Of the 7,875 participants, 7,048 wore hip accelerometers for 7 days to objectively measure physical activity, but the analytic sample included only participants who met accelerometer and performance test criteria. Grip strength was measured by dynamometry of the dominant hand and divided into quartiles (<14 kg、14 ～ 19 kg、20 ～ 24 kg、>24 kg). Chair stand performance was timed and categorized by established cut points. Time to walk 2.5 meters at a normal pace, used as a proxy for cardiorespiratory fitness, was also measured.
Mortality was tracked annually through questionnaires, national databases, and other records, and mortality was confirmed more than 99% of the time. Covariates included demographics, comorbidities, health behaviors, anthropometric measurements, and estimated lean body mass (LBM). To assess systemic inflammation, we measured some serum high-sensitivity C-reactive protein (CRP).
Strong grip strength lowers mortality risk in older women
The current study included older women with an average age of 78.7 years. Participants were an ethnically diverse group, most had some college education, and had at least one comorbidity. Baseline characteristics such as physical function, body composition, and activity level were strongly associated with quartiles of grip strength. Significant differences were found in these characteristics between survivors and decedents.
Although grip strength and chair rise time were inversely correlated, with participants with higher grip strength completing chair rise faster, reflecting improved lower body functional performance, the two measures were only moderately correlated, suggesting that they capture partially different aspects of physical function. Grip strength and chair rise time were both positively correlated with body weight.
Grip strength gradually declines with age, reflecting an age-related decline in overall muscle strength. Conversely, higher body mass index (BMI) and larger LBM were associated with increased grip strength. Variations in both grip strength and chair standing time were also observed across different racial/ethnic and BMI categories, indicating that demographic and anthropometric factors influence physical function in older adults.
During a mean follow-up of 8.3 years, 1,964 women died from any cause. Even after adjusting for demographics, health status, and objectively measured activity, higher grip strength and faster chairstand performance were each associated with a lower risk of death. Specifically, a 1 standard deviation increase in grip strength corresponded to a 12% reduction in mortality risk, although quartile-based analyzes showed a similar but weaker association with improved chair-standing performance. However, when modeled continuously by standard deviation, the association between chair and stand decreased and was no longer statistically significant after fully adjusting.
Grip strength had a consistent inverse association with mortality across subgroups, regardless of adherence to aerobic exercise guidelines, whereas chair standing time was less consistently associated. The association between grip strength and mortality was slightly attenuated but remained significant after adjusting for body weight or lean body mass.
After adjusting for inflammation based on CRP levels, the inverse association between grip strength and mortality remained significant and only slightly attenuated, whereas the association with chair-standing was shown to be further attenuated in the continuous model.
Sensitivity analyzes confirmed the robustness of our results. Grip strength remained inversely associated with mortality in most scenarios, even among women with low physical activity or using walking aids. Chair rise time was less consistently associated with mortality, especially in continuous models per standard deviation. The authors note that this may reflect the fact that chair stand performance captures broader physiological aging, fatigue susceptibility, and overall health status in addition to pure muscle strength.
conclusion
Ambulatory women aged 63 to 99 years with strong skeletal muscle strength were observed to have lower all-cause mortality, independent of other major risk factors and independent of aerobic fitness level. These results reinforce national guidelines recommending regular strength-strengthening activities for healthy aging and highlight that the results do not directly prove that strength training extends lifespan, but instead reflect an observational association.
In the future, further research is needed to determine the optimal type, intensity, and frequency of muscle-strengthening activities that provide the greatest health benefits for older adults. Additionally, longitudinal studies exploring the mechanisms by which muscle strength influences survival and the potential for tailored interventions based on physical function assessments will help refine public health strategies to promote healthy aging across diverse populations.