Effect of structured physical activity on prevention of major mobility disability in older adults: the LIFE study randomized clinical trial

Abstract

Importance: In older adults reduced mobility is common and is an independent risk factor for morbidity, hospitalization, disability, and mortality. Limited evidence suggests that physical activity may help prevent mobility disability; however, there are no definitive clinical trials examining whether physical activity prevents or delays mobility disability.

Objective: To test the hypothesis that a long-term structured physical activity program is more effective than a health education program (also referred to as a successful aging program) in reducing the risk of major mobility disability.

Design, setting, and participants: The Lifestyle Interventions and Independence for Elders (LIFE) study was a multicenter, randomized trial that enrolled participants between February 2010 and December 2011, who participated for an average of 2.6 years. Follow-up ended in December 2013. Outcome assessors were blinded to the intervention assignment. Participants were recruited from urban, suburban, and rural communities at 8 centers throughout the United States. We randomized a volunteer sample of 1635 sedentary men and women aged 70 to 89 years who had physical limitations, defined as a score on the Short Physical Performance Battery of 9 or below, but were able to walk 400 m.

Interventions: Participants were randomized to a structured, moderate-intensity physical activity program (n = 818) conducted in a center (twice/wk) and at home (3-4 times/wk) that included aerobic, resistance, and flexibility training activities or to a health education program (n = 817) consisting of workshops on topics relevant to older adults and upper extremity stretching exercises.

Main outcomes and measures: The primary outcome was major mobility disability objectively defined by loss of ability to walk 400 m.

Results: Incident major mobility disability occurred in 30.1% (246 participants) of the physical activity group and 35.5% (290 participants) of the health education group (hazard ratio [HR], 0.82 [95% CI, 0.69-0.98], P = .03).Persistent mobility disability was experienced by 120 participants (14.7%) in the physical activity group and 162 participants (19.8%) in the health education group (HR, 0.72 [95% CI, 0.57-0.91]; P = .006). Serious adverse events were reported by 404 participants (49.4%) in the physical activity group and 373 participants (45.7%) in the health education group (risk ratio, 1.08 [95% CI, 0.98-1.20]).

Conclusions and relevance: A structured, moderate-intensity physical activity program compared with a health education program reduced major mobility disability over 2.6 years among older adults at risk for disability. These findings suggest mobility benefit from such a program in vulnerable older adults.

Trial registration: clinicaltrials.gov Identifier: NCT01072500.

Figure 1

Study flow ¹Participants who did not receive the allocated intervention, i.e. attended no intervention sessions. ²For participants who did not have any MMD assessments, we assigned one hour of follow-up time, since we knew that they were able to do the 400m walk at baseline. ³Partial follow-up indicates participants who had censoring times prior to the last planned follow-up visit. ⁴Discontinuation of the intervention was operationalized as participants who did not attend at least one intervention session during their last 6-months of follow-up prior to the last planned follow-up visit date. Deaths and intervention withdrawals are included in these numbers. As an example, a participant may have discontinued the intervention in the initial six month of follow-up due to illness and then died prior to the 6-months assessment for the primary outcome. This participant would be reflected as missing the primary outcome due to death and also discontinuing the intervention.

Figure 2

Self-reported and accelerometry derived physical activity by treatment group in the LIFE study participants. Plotted values represent least squares means (95% CI) from a mixed effects model adjusting for clinical site and gender (both used to stratify randomization) and the baseline self-reported walking/weight training activities or accelerometry counts. In addition to the above mentioned terms, the model contained a term for intervention group, follow-up clinic visit (i.e. 6, 12, 18, … months) and the intervention by visit interaction. All participants had expected follow-up through 24 months and approximately 47% of randomized participants had expected visits at 36 months. Accelerometry data were not collected at the 36 month visit. Baseline values represent the overall mean of both groups combined: this is the assumed value for both groups when obtaining least squares means at follow-up using mixed effects ANCOVA. The baseline, pre-randomization value, is reflected by follow-up time 0. P-values represent tests of the average intervention effect across all visits.

Figure 3

The effect of a moderate physical activity intervention on the onset of major mobility disability and persistent mobility disability: The Life Study. Kaplan Meier plot of major mobility disability occurrence and persistent mobility disability occurrence are presented in the top and bottom panels, respectively. The graph for major mobility disability was truncated at 3.5 years and the health education group had 4 additional failures between 3.5 and 3.6 years of follow-up. Number of events represents cumulative events and adjusted hazard ratios and p-values are from proportional hazards regression models defined in the methods.

Figure 3

The effect of a moderate physical activity intervention on the onset of major mobility disability and persistent mobility disability: The Life Study. Kaplan Meier plot of major mobility disability occurrence and persistent mobility disability occurrence are presented in the top and bottom panels, respectively. The graph for major mobility disability was truncated at 3.5 years and the health education group had 4 additional failures between 3.5 and 3.6 years of follow-up. Number of events represents cumulative events and adjusted hazard ratios and p-values are from proportional hazards regression models defined in the methods.

Figure 4

Forest plot of the hazard ratio of major mobility disability for physical activity vs. health education according to sub-groups (PA= Physical Activity; HA = Health education; FG = Fasting Glucose). P-values were obtained from likelihood ratios tests of the interaction terms added to the Cox regression model.