Association of physical function with connectivity in the sensorimotor and dorsal attention networks: why examining specific components of physical function matters.

Declining physical function with aging is associated with structural and functional brain network organization. Gaining a greater understanding of network associations may be useful for targeting interventions that are designed to slow or prevent such decline. Our previous work demonstrated that the Short Physical Performance Battery (eSPPB) score and body mass index (BMI) exhibited a statistical interaction in their associations with connectivity in the sensorimotor cortex (SMN) and the dorsal attention network (DAN). The current study examined if components of the eSPPB have unique associations with these brain networks. Functional magnetic resonance imaging was performed on 192 participants in the BNET study, a longitudinal and observational trial of community-dwelling adults aged 70 or older. Functional brain networks were generated for resting state and during a motor imagery task. Regression analyses were performed between eSPPB component scores (gait speed, complex gait speed, static balance, and lower extremity strength) and BMI with SMN and DAN connectivity. Gait speed, complex gait speed, and lower extremity strength significantly interacted with BMI in their association with SMN at rest. Gait speed and complex gait speed were interacted with BMI in the DAN at rest while complex gait speed, static balance, and lower extremity strength interacted with BMI in the DAN during motor imagery. Results demonstrate that different components of physical function, such as balance or gait speed and BMI, are associated with unique aspects of brain network organization. Gaining a greater mechanistic understanding of the associations between low physical function, body mass, and brain physiology may lead to the development of treatments that not only target specific physical function limitations but also specific brain networks.

A community-based physical activity intervention to prevent mobility-related disability for retired older people (REtirement in ACTion (REACT)): study protocol for a randomised controlled trial.

BACKGROUND: The REtirement in ACTion (REACT) study is a multi-centre, pragmatic, two-arm, parallel-group randomised controlled trial (RCT) with an internal pilot phase. It aims to test the effectiveness and cost-effectiveness of a community, group-based physical activity intervention for reducing, or reversing, the progression of functional limitations in older people who are at high risk of mobility-related disability. METHODS/DESIGN: A sample of 768 sedentary, community-dwelling, older people aged 65 years and over with functional limitations, but who are still ambulatory (scores between 4 and 9 out of 12 in the Short Physical Performance Battery test (SPPB)) will be randomised to receive either the REACT intervention, delivered over a period of 12 months by trained facilitators, or a minimal control intervention. The REACT study incorporates comprehensive process and economic evaluation and a nested sub-study which will test the hypothesis that the REACT intervention will slow the rate of brain atrophy and of decline in cognitive function assessed using magnetic resonance imaging (MRI). Outcome data will be collected at baseline, 6, 12 and 24 months for the main study, with MRI sub-study data collected at baseline, 6 and 12 months. The primary outcome analysis (SPPB score at 24 months) will be undertaken blinded to group allocation. Primary comparative analyses will be on an intention-to-treat (ITT) basis with due emphasis placed on confidence intervals. DISCUSSION: REACT represents the first large-scale, pragmatic, community-based trial in the UK to target the non-disabled but high-risk segment of the older population with an intervention to reduce mobility-related disability. A programme that can successfully engage this population in sufficient activity to improve strength, aerobic capacity, coordination and balance would have a major impact on sustaining health and independence. REACT is also the first study of its kind to conduct a full economic and comprehensive process evaluation alongside the RCT. If effective and cost-effective, the REACT intervention has strong potential to be implemented widely in the UK and elsewhere. TRIAL REGISTRATION: ISRCTN, ID: ISRCTN45627165 . Retrospectively registered on 13 June 2016. Trial sponsor: University of Bath. Protocol Version 1.5.

Imputation of Gait Speed for Noncompleters in the 400-Meter Walk: Application to the Lifestyle Interventions for Elders Study.

When a 400-m walk test with time constraint (in 15 minutes) is administered, analysis of the associated 400-m gait speed can be challenging because some older adults are unable to complete the distance in time (noncompleters). A simplistic imputation method is to calculate the observed speeds of the noncompleters as the partially completed distance divided by the corresponding amount of elapsed time as an estimate of gait speed over the full 400-m distance. This common practice has not been validated to the best of our knowledge. We propose a Bayesian multiple imputation (MI) method to impute the unobserved 400-m gait speed for noncompleters. Briefly, MI is performed under the assumption that the unobserved 400-m gait speed of noncompleters is left-censored from a normal distribution. We illustrate the application of the Bayesian MI method using longitudinal data collected from the Lifestyle Interventions for Elders (LIFE) study. A simulation study was performed to assess the bias in estimation of the mean 400-m gait speed using both methods. The results indicate that the simplistic imputation method tends to overestimate the population mean, whereas the Bayesian MI method yields minimal bias as the sample size increases.

Hospitalizations During a Physical Activity Intervention in Older Adults at Risk of Mobility Disability: Analyses from the Lifestyle Interventions and Independence for Elders Randomized Clinical Trial.

OBJECTIVES: To determine whether moderate-intensity physical activity (PA) and health education (HE) are differentially associated with categories of hospitalizations or subgroups of participants. DESIGN: Multicenter randomized controlled trial in which participants were randomized to a PA or HE program for an average of 2.6 years. SETTING: Eight field centers. PARTICIPANTS: Sedentary men and women aged 70-89 with lower extremity physical limitations but able to walk 400-m in 15 minutes or less (N = 1,635). INTERVENTIONS: Structured, moderate-intensity PA (n =  818) at a center (2×/wk) and at home (3-4×/wk) that included aerobic, strength, balance, and flexibility training or HE (n =  817) of educational workshops and upper extremity stretching exercises. MEASUREMENTS: All-cause inpatient hospitalizations ascertained at 6-month intervals. RESULTS: There were 1,458 hospitalizations (49.1% of PA, 44.4% of HE; risk difference = 4.68%, 95% confidence interval (CI) = -0.18-9.54; hazard ratio (HR) = 1.16, 95% CI = 1.00-1.34). The intervention effect on incident hospitalization did not differ according to race, sex, Short Physical Performance Battery score, age, or history of cardiovascular disease or diabetes mellitus. PA was associated with higher rates of hospitalization in the middle baseline gait speed category, than HE (<0.8 m/s: HR = 0.93, 95% CI = 0.76-1.14; 0.8-1.0 m/s: HR = 1.54, 95% CI = 1.23-1.94; >1.0 m/s: HR = 1.05, 95% CI = 0.67-1.65; interaction P = .005). CONCLUSION: A PA program in older adults at risk for mobility disability did not lead to a different risk of specific types of hospitalizations than a HE program overall. Baseline gait speed may be a marker for risk of hospitalization during a PA intervention, because individuals with moderate baseline gait speed in the PA group had slightly higher rates of hospitalization than those in the HE group. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01072500.