Relationships Between Profiles of Physical Activity and Major Mobility Disability in the LIFE Study

Abstract

Objectives: To examine the relationship between time spent in light physical activity (LPA) and in moderate to vigorous physical activity (MVPA) and the pattern of accumulation on the risk for major mobility disability (MMD) in a large multicenter study of physical activity (PA) and aging, the Lifestyle Interventions and Independence for Elders (LIFE) study.

Design: Data were collected from individuals randomized to a PA intervention as part of the LIFE study, an eight-center single-blind randomized clinical trial conducted between February 2010 and December 2013.

Setting: Lifestyle Interventions and Independence for Elders Study PARTICIPANTS: Older adult participants (78.4 years; N = 507) at risk for MMD.

Intervention: All older adults included in these analyses were randomized to a structured PA intervention that included two center-based plus three to four home-based exercise sessions per week with a primary goal of walking for 150 minutes weekly. Participants attended the intervention for 2.5 years on average.

Measurements: MMD was defined as the inability to complete a 400-m walk within 15 minutes and without assistance. Physical function was assessed via the Short Physical Performance Battery (SPPB). Actigraph accelerometers were used to quantify amount and variability in LPA and MVPA.

Results: In an adjusted Cox proportional hazards regression, we identified a significant interaction (P = .017) between SPPB score and LPA amount and variability such that more LPA was associated with a reduced risk for MMD among those with higher initial function, as was lower variability (eg, via distributing LPA across the day). The SPPB × MVPA interaction was significant (P = .04), such that more MVPA was associated with lower MMD risk among those with lower function. Finally, greater MVPA variability was associated with lower risk for MMD.

Conclusion: A prescription of PA for older adults should account for key factors such as physical function and emphasize both amount and pattern of accumulation of PA from across the intensity continuum. J Am Geriatr Soc 68:1476-1483, 2020.

Trial registration: ClinicalTrials.gov NCT01072500.

Keywords: function; mobility; physical activity; sedentary behavior.

Figure 1.

Illustration of two individuals with similar average daily minutes of LPA, and high (solid line) vs low (dashed line) LPA variability.

Figure 2.

Participant Flow. Notes: ¹Participants who did not receive the allocated intervention (i.e. attended no intervention sessions); ²Discontinuation 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.

Figure 3.

Illustration of the difference in risk for MMD that a 1-unit higher level of variability has at different amounts of LPA (vertical lines), and difference in risk associated with a 1-min/hr higher level of amount at different levels of variability in LPA (horizontal lines) among those with a short physical performance battery (SPPB) score ≤ 7 (bottom panel) and SPPB = 8–9, extracted from a model including all activity predictors. Note that we have illustrated variability hazard ratios at selected values of 6 vs. 5, 9 vs. 8, and 11 vs. 10, and amount hazard ratios at selected values of 7 vs. 6 min/hour, 13 vs. 12 min/hour, and 17 vs. 16 min/hour. Red dots represent activity measurement intervals followed by MMD events. HRs for LPA were obtained through back-transformation from models generated using log-transformed values of LPA.

Figure 4.

Change in accelerometer counts per minute (median difference per day) in the first six months of the intervention by short physical performance battery score.