Reference values and correlations for multiple physical performance measures: a prospective cross-sectional study among independently mobile older men in Japan

Background: As the most rapidly aging country in the world, Japan is one of few countries with a male life expectancy over 80 years. The gap between the healthy life span and the total life expectancy is large, highlighting the importance of maintaining physical performance (e.g., walking speed, grip strength, and standing balance) in later life, which is also negatively associated with mortality among older adults. The present study aimed to establish reference values for multiple physical performance measures among high-functioning oldest-old Japanese men and to investigate the correlations among these measurements to understand how these variables are related in a more detailed and objective way, compared with previous studies. Methods: This single-center prospective cross-sectional study was conducted from September 2018 to August 2019 with 120 male orthopedic patients in Japan who were able to walk independently. Seven measures of physical performance were assessed: handgrip strength, quadriceps strength, static balance ability (one-legged stance), dynamic balance ability (Functional Reach Test; FRT), walking ability (5-m walking time test), combined movement ability (Timed Up & Go test), and bone quality. Cognitive function was also measured (Mini-Mental State Examination; MMSE). Spearman’s rank correlation was used to evaluate correlations between the variables. Results: Specific reference values are reported for each physical performance measurement explored in this study. Only six participants were classified as cognitively impaired, and 16 had mild cognitive impairment. There were significant correlations of varying levels among all of the measures of physical performance. Age was significantly correlated with all performance measures except FRT, and there was no correlation between age and MMSE. MMSE was weakly correlated with FRT and unrelated to the other performance measures. Conclusions: The reference ranges from this study among a high-functioning cohort of men aged 80 years or older can be used by older men who have not yet reached this age and their health care providers as physical performance targets to facilitate the maintenance of independent mobility in later life. There is an urgent need for the establishment of exercise interventions that will allow these men to achieve the desired targets, potentially lengthening their healthy life span.