Whole-Body and Segmental Phase Angles and Cognitive Function in the Older Korean Population: Cross- Sectional Analysis

Background: Recently, the phase angle (PhA) has emerged as an essential indicator of cellular health. Most studies have examined its association with physiological conditions, such as sarcopenia, frailty, and physical function, in older populations. Simultaneously, growing attention is being paid to the clinical relevance of segmental PhAs for future applications. However, few studies have explored the relationship between PhAs, especially segmental PhAs, and the psychological aspects of health, particularly cognitive function. Objective: We aimed to investigate the association between whole-body and segmental PhAs and cognitive function in older adults. Methods: Individuals aged 65 years and above were recruited from adult community groups residing in Busan, South Korea, through the 2022 Bus-based Screening and Assessment Network (BUSAN) study of Pusan National University Hospital. Participants' whole-body and segmental PhAs were measured using a bioelectrical impedance analyzer (BWA 2.0 Body Water Analyzer, InBody), and cognitive functions (overall and subdomains, including memory, orientation, attention and calculation, and language) were self-reported using the Korean version of the Mini-Mental State Examination. Multiple linear regression analyses were performed to examine these associations. Results: This study included 625 older adults aged 65-96 years (women: n=444, 71%; men: n=191, 29%). A positive association was observed between whole-body PhA and cognitive function (b=0.62, 95% CI 0.16-1.08; P<.01). We observed significant positive associations between the PhA of the lower limbs (b=0.72, 95% CI 0.38-1.06; P<.001) and cognitive function. Analysis of the Mini-Mental State Examination subdomains revealed that whole-body PhA was significantly related to memory (b=0.11, 95% CI 0.00-0.22; P=.04); the PhA of the upper limbs was significantly related to orientation (b=0.29, 95% CI 0.09-0.49; P=.01); and the PhA of the lower limbs was significantly related to orientation (b=0.24, 95% CI 0.10-0.38; P<.001), attention and calculation (b=0.21, 95% CI 0.06-0.37; P=.01), memory (b=0.14, 95% CI 0.05-0.22; P=.001), and language functions (b=0.07, 95% CI 0.01-0.12; P=.01). However, trunk PhA showed no significant association. Conclusions: Our findings bolster the emerging evidence of a significant positive correlation between whole-body PhA and cognitive function in our sample, with nuanced relationships observed across different segmental PhAs and cognitive subdomains. Therefore, this study revealed that PhAs could be a useful tool for screening or preventing cognitive decline in the general older population, offering substantial evidence for future interventional studies. Further research should delve into the mechanisms and assess targeted interventions that enhance regional physical function to support cognitive health in older adults. Further long-term investigation on these associations is warranted.