Objectives C-terminal Agrin Fragment (CAF) has been proposed as a potential circulating biomarker for predicting changes in physical function among older adults. To determine the effect of a one-year PA intervention on changes in CAF concentrations and to evaluate baseline and longitudinal associations between CAF concentrations and indices of physical function. Design Ancillary study to the Lifestyle Interventions and Independence for Elders Pilot (LIFE-P), a multi-site randomized clinical trial designed to evaluate the effects of chronic exercise on the physical function of older adults at risk for mobility disability. Setting Four academic research centers within the U.S. Participants Three hundred thirty three older adults aged 70 to 89 with mild to moderate impairments in physical function. Intervention A 12-month intervention of either structured physical activity (PA) or health education promoting successful aging (SA). Measurements Serum CAF concentrations and objectives measures of physical function – i.e. gait speed and performance on the Short Physical Performance Battery (SPPB). Results The group*time interaction was not significant for serum CAF concentrations (p=0.265), indicating that the PA intervention did not significantly reduce serum CAF levels compared to SA. Baseline gait speed was significantly correlated with baseline CAF level (r = −0.151, p= 0.006), however the association between CAF and SPPB was not significant. Additionally, neither baseline nor the change in CAF concentrations strongly predicted the change in either performance measure following the PA intervention. Conclusion In summary, the present study shows that a one-year structured PA program did not reduce serum CAF levels among mobility-limited older adults. However, further study is needed to definitively determine the utility of CAF as a biomarker of physical function.

BackgroundData are sparse regarding the value of physical activity (PA) surveillance among older adults—particularly among those with mobility limitations. The objective of this study was to examine longitudinal associations between objectively measured daily PA and the incidence of cardiovascular events among older adults in the LIFE (Lifestyle Interventions and Independence for Elders) study.Methods and ResultsCardiovascular events were adjudicated based on medical records review, and cardiovascular risk factors were controlled for in the analysis. Home‐based activity data were collected by hip‐worn accelerometers at baseline and at 6, 12, and 24 months postrandomization to either a physical activity or health education intervention. LIFE study participants (n=1590; age 78.9±5.2 [SD] years; 67.2% women) at baseline had an 11% lower incidence of experiencing a subsequent cardiovascular event per 500 steps taken per day based on activity data (hazard ratio, 0.89; 95% confidence interval, 0.84–0.96; P=0.001). At baseline, every 30 minutes spent performing activities ≥500 counts per minute (hazard ratio, 0.75; confidence interval, 0.65–0.89 [P=0.001]) were also associated with a lower incidence of cardiovascular events. Throughout follow‐up (6, 12, and 24 months), both the number of steps per day (per 500 steps; hazard ratio, 0.90, confidence interval, 0.85–0.96 [P=0.001]) and duration of activity ≥500 counts per minute (per 30 minutes; hazard ratio, 0.76; confidence interval, 0.63–0.90 [P=0.002]) were significantly associated with lower cardiovascular event rates.ConclusionsObjective measurements of physical activity via accelerometry were associated with cardiovascular events among older adults with limited mobility (summary score >10 on the Short Physical Performance Battery) both using baseline and longitudinal data.Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT01072500.

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Introduction: Objective measurement of daily physical activity (PA) is an important predictor of cardiovascular risk among young- and middle-aged adults. However, data are sparse regarding the value of activity monitoring among older adults [[Unable to Display Character: –]] particularly among those with mobility limitations. Hypothesis: We hypothesized that objectively-measured daily PA would be associated with the incidence of cardiovascular (CV) events among older adults in the Lifestyle Interventions and Independence for Elders (LIFE) study [[Unable to Display Character: –]] a Phase 3 randomized clinical trial comparing a structured exercise intervention (median 2.7 years) to health education among mobility-limited older adults. Methods: CV events (myocardial infarction, stroke, cardiovascular death, silent myocardial infarction, angina/symptomatic coronary artery disease, peripheral artery disease, abdominal aortic aneurysm) were adjudicated by medical records review. Free-living activity data were collected by hip-worn accelerometer at baseline and 6, 12, and 24 months post-randomization. Linear regression, adjusted for accelerometer wear time, demographic and cardiovascular disease-related covariates, was used to model the relationship of incident CV events with accelerometry variables (steps/day and minutes/day spent in activity registering ≥ 100 or ≥ 500 counts/minute) at baseline and in a time-dependent fashion. Results: Participants (n = 1618; age 78.9 ± [SD] 5.2 years; 67.2% female) had a cumulative CV event incidence rate of 14.5% (234 events). Event rates did not differ between randomized groups. At baseline, participants registered 2681 ± 1475 steps/day and spent 22.8 ± 8.2% of their time performing activities≥ 100 cts/min and 6.3 ± 4.3% of time in activities ≥ 500 cts/min. At baseline, CV event risk was10% lower for every 500 steps/day (HR: 0.90, 95% CI: 0.84-0.96, p=0.001). Each 30 minutes spent performing activities ≥ 100 cts/min (0.89, CI: 0.83-0.96, p=0.002) and ≥ 500 cts/min (HR = 0.76, CI: 0.65-0.90, p=0.001) was also associated with lower CV event risk. Across all follow-up visits, participants took 2544 ± 1592 steps/day and spent 21.3 ± 8.2% of their time performing activities> 100 cts/min and 5.8± 4.3% of time in activities ≥ 500 cts/min. In time-dependent analyses, both steps/day (HR: 0.92, CI: 0.86-0.97, p=0.004) and duration of activity ≥ 500 counts/min (HR: 0.80, CI: 0.68-0.94, p=0.007) were associated with lower CV event rates. Longitudinal performance of activity ≥ 100 cts/min was not statistically significant (HR: 0.93, CI: 0.87-1.01, p=0.067). Conclusions: Objective measurements of PA collected via accelerometry predicted incident CV events among older adults with limited mobility. These data support the importance of daily PA in this population and suggest that accelerometry may be a useful tool to aid in assessing the risk of CV events.

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