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Background: The aim of this study was to determine the relative and absolute reliabilities of 5 key performance-based measures of physical function in the Canadian Longitudinal Study on Aging (CLSA).Methods: An age-stratified subsample of 147 participants from the CLSA who were undergoing their 3-year data collection visit participated in 2 repeat visits (within 1 week). Participants underwent tests of grip strength, 4-m gait speed, Timed Up and Go (TUG), chair rise, and single-leg stance (left, right, mean, maximum). Intraclass correlation coefficients (ICCs), standard error of measurement, and minimal detectable change (MDC) values were calculated.Results: The relative reliability for grip strength was excellent (ICC = 0.95); the TUG and single-leg stance tests had good reliability (ICC = 0.80 or 0.78-0.82, respectively); gait speed and the chair-rise test had moderate reliability (ICC = 0.64 for both) for participants overall. For participants between 50 and 64 years, TUG and gait speed had poor reliabilities (ICC = 0.38 or 0.33, respectively). For participants aged 75 years and older, the single-leg stance had poor reliability (ICC = 0.30-0.39). The MDC90 was about 6 kg for grip strength, 2.3 seconds for TUG, 0.2 m/second for gait speed, 5.2 seconds for chair rise, and ranged from 22.8 to 26.2 seconds for the single-leg stance.Conclusions: Among community-dwelling Canadians older than 50 years, the reliabilities of the CLSA measures were moderate to excellent. The TUG and gait speed in the youngest age group, and the single-leg stance in the oldest age group, showed poor reliability. MDC values can be used to interpret changes over time. [ABSTRACT FROM AUTHOR]

Many studies have shown that estimates of biological age (BA) can predict health-related outcomes in older adults. Often, researchers employ multiple measures belonging to a variety of biological/physiological systems, and assess the validity of BA estimates by how well they approximate chronological age (CA). However, it is not clear whether this is the best approach for judging a BA estimate, or whether certain groups of measures are more informative to this end. Using data from the Canadian Longitudinal Study on Aging, we composed panels of biological measures based on the physiological systems/domains they belong to (blood, organ function, physical/cognitive performance), and also composed a panel of measures that optimized the association of BA with CA. We then compared BA estimates for each according to their association with CA and health-related outcomes, including frailty, multimorbidity, chronic condition domains, disability, and health care utilization. Although BA estimated using all 40 measures (r = 0.74) or our age-optimized panel (r = 0.77) most closely approximated CA, the strength of associations to health-related outcomes was comparable or weaker than that of our panel composed only of physical performance measures (CA r = 0.59). All BA estimates were significantly associated to the outcomes considered, with exception to the neurological and musculoskeletal disease domains, and only varied slightly by sex. In summary, while the approximation of CA is important to consider when estimating BA, the strength of associations to prospective outcomes may be of greater importance. Hence, the context in which BA is estimated should be influenced by an investigator's specific research goals. [ABSTRACT FROM AUTHOR]

• Elevated Allostatic Load Index determines worse physical performance states in older adults. • Distributions of Allostatic Load Averages do not differ significantly among the cities evaluated. • Total and Indirect Mediation Effects between Allostatic Load and the variables of age, socioeconomic and chronic conditions on physical performance scores were evidenced. This study aimed to evaluate the association between Allostatic Load (AL) and physical performance scores in older adults from four cities in North and South America. In this cross-sectional study, data from 1101 volunteers from three countries (Canada, Brazil, and Colombia) from the International Mobility in Aging Study (IMIAS) were used to evaluate the association between AL index and Short Physical Performance Battery (SPPB) scores. Three multiple linear regression models adjusted by age, Socioeconomic Status (SES), chronic conditions, depression symptoms, and Leganés Cognitive Test (LCT) were developed to estimate the independent association between SPPB and AL. Mediation analysis with 2012 LA data and covariates was performed to access the total, direct, and indirect effects of mediation on SPPB scores from 2016. AL and SPPB were inversely associated, with older adults with high allostatic load scoring lower on SPPB (β: -0.234, Std: 0.033, p-value: <0.001). Indirect effects were evidenced between age, SES and chronic conditions with AL and SPPB scores. Chronic conditions also had a total effect on SPPB scores and were also mediated by AL. However, indirect effects of depressive symptoms and LCT on SPPB scores mediated by AL were not observed. Findings from this study support that increased AL index determines worse physical performance states after full adjustments. AL has a mediator role between the number of chronic diseases, depressive symptoms, cognitive status and physical performance. Socioeconomic status also influenced physical scores mediated by the AL index. [ABSTRACT FROM AUTHOR]