IS THERE A THRESHOLD BETWEEN PEAK OXYGEN-UPTAKE AND SELF-REPORTED PHYSICAL FUNCTIONING IN OLDER ADULTS

Purpose: Few studies have examined the relationship between directly m easured oxygen uptake ((V) over dot O-2) and self-reported physical fu nction (PF). The purpose of this study was: 1) to examine the relation ship between peak (V) over dot O-2 and PF and 2) to determine whether a threshold or cut point exists that distinguishes between individuals reporting required assistance in the performance of functional tasks (low PF) and those who report ability to perform tasks independently ( high PF). Methods: Participants were 161 community-dwelling adults, ag es 65-90, who had a baseline evaluation for a clinical trial that incl uded measurement of peak (V) over dot O-2 and PF. PF consisted of a su mmary score combining scores from the Older Americans Resources and Se rvices Multidimensional Functional Assessment Questionnaire, Nagi Disa bility Study, Rosow-Breslau Scale, Physical Function Scale of the Medi cal Outcomes Study, and the Falls Efficacy Scale. Decision tree, cubic spline, and logistic regression analyses explored these relationships with age, gender, education, race, body mass index, depression, and t otal number of chronic diseases included as important covariates. Resu lts: Among all covariates examined, peak (V) over dot O-2 was most str ongly associated with (P = 0.004) with PF. There was no threshold effe ct. Decision tree analyses indicated that 18.3 mL . kg(-1) . min(-1) w as the optimal cut point distinguishing between low PF and high PF (P < 0.0001). Between-gender differences in PF(P = 0.002) were no longer significant when peak (V) over dot O-2 was included in the PF model (P = 0.17). Conclusions: These data indicate that individuals with a pea k (V) over dot O-2 < 18 mL . k(-1) . min(-1) report significant diffic ulty in the performance of daily tasks and that differences in peak (V ) over dot O-2 may explain, in part, why women report more impairment in PF.