Associations of socio-demographic, anthropometric and behavioural factors with phase angle in older adults: a cross-sectional study in Taiwan.

Objective: Phase angle (PhA) is a prognostic factor for predicting and monitoring geriatric syndromes. However, multiple factors associated with increased PhA values as an outcome remain unclear in the older population. This study aimed to examine the association of socio-demographic, anthropometric and behavioural factors with PhA among older Taiwanese adults.

Design: This cross-sectional study was conducted between May and August 2023.

Setting: The study was carried out in northern Taiwan, specifically Taipei city and Yilan county.

Participants: Participants aged ≥65 years who were able to walk independently and had no artificial implants, such as cardiac pacemakers or joint replacements, were recruited using convenience sampling. A total of 198 participants were initially recruited for this study.

Primary Outcome Measures: Data on socio-demographic and behavioural variables were collected using self-administered questionnaires. Anthropometric variables and PhA were measured using a multi-frequency bioelectrical impedance analyser (MC-780MA, TANITA). PhA was categorised into 'high' and 'low' using gender-specific cut-off points. A logistic regression analysis was performed.

Results: A total of 152 participants (mean age: 72.0±5.5 years; 121 women (79.6%)) were included. Male (OR=0.72, 95% CI=0.02 to 0.33), unmarried (OR=0.22, 95% CI=0.06 to 0.82) and unemployed older adults (OR=0.16, 95% CI=0.03 to 0.87) were less probable to achieve high PhA values. After adjusting for potential confounders, older individuals with an increased body mass index (BMI) (OR=2.56, 95% CI=1.61 to 4.07) and greater muscle mass (OR=1.34, 95% CI=1.12 to 1.60) may have higher PhA values, whereas those with a greater fat mass may have lower PhA values (OR=0.61, 95% CI=0.48 to 0.78). No significant associations were observed between behavioural factors and PhA values.

Conclusions: The interventions designed to improve PhA should prioritise strategies tailored to male, unmarried or unemployed older adults, as well as those with low BMI, low muscle mass and high fat mass. Future studies with larger sample sizes are needed to confirm and strengthen our findings.