As populations worldwide continue to age, the urgency of preventing functional decline and mitigating the future need for long-term care among older adults is becoming increasingly apparent. A straightforward method for evaluating an individual’s physical condition involves using body composition analysers, particularly for assessing muscle mass. However, emerging research has cast doubt on the reliability of muscle mass alone as a predictor of health outcomes, highlighting instead the importance of assessing “muscle quality”—a more nuanced and potentially informative metric.
Body composition analysers transmit a weak alternating electrical current through the body and measure its resistance. By employing currents at multiple frequencies, these devices can provide insight into the physiological state of cell membranes—quantified as the phase angle—as well as the ratio of intracellular water (ICW) to extracellular water (ECW), both of which serve as proxies for tissue integrity and function. Numerous studies have demonstrated that such measures can distinguish between tissues that contribute to muscle contraction and those that do not, effectively offering an index of muscle quality. Since the ability of muscles to contract is vital for performing everyday activities, indicators of muscle quality may correlate more directly with future risk of functional impairment and consequent dependence on long-term care.
In this context, a longitudinal study was conducted using body composition data from 858 adults aged 65 years or older residing in Kasama City, Ibaraki Prefecture, Japan. The researchers focused on two indicators derived from bioelectrical impedance analysis: the phase angle and the extracellular to intracellular water resistance ratio. These individuals were monitored over 12 years to investigate the association between these physiological markers and the eventual need for long-term care services.
The findings revealed a compelling relationship: individuals exhibiting lower values for the phase angle and the ECW/ICW resistance ratio—particularly in the lower limbs—faced a significantly increased risk of becoming dependent on long-term care. This association was most pronounced when these values fell below the cohort median. In contrast, conventional muscle mass measurements did not correlate statistically with the onset of care dependency. These results underscore the limitations of traditional metrics and suggest that indices reflecting muscle quality may be more predictive of future frailty.
To translate these findings into practical application, the researchers established standard reference values for each indicator, estimating thresholds that signify increased risk of dependency within four and ten years, respectively. Such benchmarks serve as valuable tools for early intervention strategies, allowing health professionals and policymakers to identify at-risk individuals and implement preventive measures more effectively.
Importantly, body composition analysers offer several logistical advantages. The assessment process is non-invasive and requires minimal effort from the subject—simply stepping onto the device initiates the measurement—and no specialised personnel are needed to operate the machinery. This ease of use applies well to implementation in diverse settings, including medical clinics, long-term care facilities, and community centres. With widespread adoption, such technology could become an essential component of public health strategies aimed at reducing the incidence of care dependency in older populations, ultimately improving quality of life and reducing the societal burden associated with ageing.
More information: Yujiro Asano et al, Segmental phase angle and the extracellular to intracellular water ratio are associated with functional disability in community-dwelling older adults: A follow-up study of up to 12 years, Nutrition. DOI: 10.1016/j.nut.2025.112709
Journal information: Nutrition Provided by University of Tsukuba
