B. Penninx

OBJECTIVES: To define clinically relevant cutpoints for usual gait speed and to investigate their predictive value for health-related events in older persons. DESIGN: Prospective cohort study. SETTING: Health, Aging and Body Composition Study. PARTICIPANTS: Three thousand forty-seven well-functioning older persons (mean age 74.2). MEASUREMENTS: Usual gait speed on a 6-m course was assessed at baseline. Participants were randomly divided into two groups to identify (Sample A; n=2,031) and then validate (Sample B; n=1,016) usual gait-speed cutpoints. Rates of persistent lower extremity limitation events (mean follow-up 4.9 years) were calculated according to gait speed in Sample A. A cutpoint (defining high- (< 1 m/s) and low risk (> or = 1 m/s) groups) was identified based on persistent lower extremity limitation events. The predictive value of the identified cutpoints for major health-related events (persistent severe lower extremity limitation, death, and hospitalization) was evaluated in Sample B using Cox regression analyses. RESULTS: A graded response was seen between risk groups and health-related outcomes. Participants in the high-risk group had a higher risk of persistent lower extremity limitation (rate ratio (RR)=2.20, 95% confidence interval (CI)=1.76-2.74), persistent severe lower extremity limitation (RR=2.29, 95% CI=1.63-3.20), death (RR=1.64, 95% CI=1.14-2.37), and hospitalization (RR=1.48, 95% CI=1.02-2.13) than those in the low-risk group. CONCLUSION: Usual gait speed of less than 1 m/s identifies persons at high risk of health-related outcomes in well-functioning older people. Provision of a clinically meaningful cutpoint for usual gait speed may facilitate its use in clinical and research settings.

BACKGROUND: The serum concentration of interleukin 6 (IL-6), a cytokine that plays a central role in inflammation, increases with age. Because inflammation is a component of many age-associated chronic diseases, which often cause disability, high circulating levels of IL-6 may contribute to functional decline in old age. We tested the hypothesis that high levels of IL-6 predict future disability in older persons who are not disabled. METHODS: Participants at the sixth annual follow-up of the Iowa site of the Established Populations for Epidemiologic Studies of the Elderly aged 71 years or older were considered eligible for this study if they had no disability in regard to mobility or in selected activities of daily living (ADL), and they were re-interviewed 4 years later. Incident cases of mobility-disability and of ADL-disability were identified based on responses at the follow-up interview. Measures of IL-6 were obtained from specimens collected at baseline from the 283 participants who developed any disability and from 350 participants selected randomly (46.9%) from those who continued to be non-disabled. FINDINGS: Participants in the highest IL-6 tertile were 1.76 (95% CI, 1.17-2.64) times more likely to develop at least mobility-disability and 1.62 (95% CI, 1.02-2.60) times more likely to develop mobility plus ADL-disability compared with to the lowest IL-6 tertile. The strength of this association was almost unchanged after adjusting for multiple confounders. The increased risk of mobility-disability over the full spectrum of IL-6 concentration was nonlinear, with the risk rising rapidly beyond plasma levels of 2.5 pg/mL. INTERPRETATION: Higher circulating levels of IL-6 predict disability onset in older persons. This may be attributable to a direct effect of IL-6 on muscle atrophy and/or to the pathophysiologic role played by IL-6 in specific diseases.

OBJECTIVES: To determine how three different physical performance measures (PPMs) combine for added utility in predicting adverse health events in elders. DESIGN: Prospective cohort study. SETTING: Health, Aging and Body Composition Study. PARTICIPANTS: Three thousand twenty-four well-functioning older persons (mean age 73.6). MEASUREMENTS: Timed gait, repeated chair stands, and balance (semi- and full-tandem, and single leg stands each held for 30 seconds) tests were administered at baseline. Usual gait speed was categorized to distinguish high- and low-risk participants using the previously established 1-m/s cutpoint. The same population-percentile (21.3%) was used to identify cutpoints for the repeated chair stands (17.1 seconds) and balance (53.0 seconds) tests. Cox proportional hazard analyses were performed to evaluate the added value of PPMs in predicting mortality, hospitalization, and (severe) mobility limitation events over 6.9 years of follow-up. RESULTS: Risk estimates for developing adverse health-related events were similarly large for each of the three high-risk groups considered separately. Having more PPM scores at the high-risk level was associated with a greater risk of developing adverse health-related events. When all three PPMs were considered, having only one poor performance was sufficient to indicate a highly significantly higher risk of (severe) lower extremity and mortality events. CONCLUSION: Although gait speed is considered to be the most important predictor of adverse health events, these findings demonstrate that poor performance on other tests of lower extremity function are equally prognostic. This suggests that chair stand and standing balance performance may be adequate substitutes when gait speed is unavailable.