Abstract

Importance: Identifying factors contributing to sustained physical functioning is critical for the health and well-being of the aging population, especially as physical functioning may precede and predict subsequent health outcomes. Prior work suggests optimism may protect health, but less is known about the association between optimism and objective physical functioning measures as individuals age.

Objective: To evaluate the longitudinal association between optimism and 3 physical functioning measures.

Design, setting, and participants: This was a prospective cohort study using data from the Women's Health Initiative (WHI) with participants recruited from 1993 to 1998 and followed up over 6 years. Data analysis was conducted from January 2022 to July 2022. Participants included postmenopausal women older than 65 years recruited from 40 clinical centers in the US.

Exposure: Optimism was assessed at baseline using the Life Orientation Test-Revised.

Main outcomes and measures: Physical functioning was measured at 4 time points across 6 years by study staff evaluating performance in grip strength, timed walk, and chair stands.

Results: The final analytic sample included 5930 women (mean [SD] age, 70 [4] years). Linear mixed-effects models controlling for demographics, depression, health status, and health behaviors showed that higher optimism was associated with higher grip strength (β = 0.36; 95% CI, 0.21-0.50) and number of chair stands (β = 0.05; 95% CI, 0.01-0.10) but not timed walk at baseline. Higher optimism was also associated with slower rates of decline in timed walk (β = -0.09; 95% CI, -0.13 to -0.04) and number of chair stands (β = 0.01; 95% CI, 0-0.03) but not grip strength over time. Cox proportional hazards models showed that higher optimism was associated with lower hazards of reaching clinically defined thresholds of impairment for all 3 outcomes over 6 years of follow-up. For example, in fully adjusted models, for a 1-SD increase in optimism, hazard ratios for reaching impairment thresholds were 0.86 (95% CI, 0.80-0.92) for grip strength, 0.94 (95% CI, 0.88-1.01) for timed walk, and 0.91 (95% CI, 0.85-0.98) for chair stands.

Conclusion and relevance: In this cohort study of postmenopausal women, at baseline, higher optimism was associated with higher grip strength and number of chair stands but not with the time it took to walk 6 m. Higher optimism at baseline was also associated with maintaining healthier functioning on 2 of the 3 performance measures over time, including less decline in walking speed and in number of chair stands women could perform over 6 years of follow-up. Given experimental studies suggesting that optimism is modifiable, it may be a promising target for interventions to slow age-related declines in physical functioning. Future work should explore associations of optimism with maintenance of physical functioning in diverse populations.