Factors Influencing Longitudinal Stair Climb Performance from Midlife to Early Late Life: The Study of Women’s Health Across the Nation Chicago and Michigan Sites

Abstract

Objectives: To quantify the longitudinal change in stair climb performance (a measure indicative of both physical function and muscle power), determine whether physical activity is related to slower decline in performance, and to identify factors that modify the longitudinal change in performance among women from midlife to late life. Design: Longitudinal cohort study with up to 15 study visits. Setting: Two sites of the Study of Women’s Health Across the Nation. Participants: Black (n=411) and white (N=419) women followed from median age 47.0 (44.6–49.6) to 62.0 (55.8–65.3) years. Interventions: N/A. Measurements: Performance on a stair climb test (ascend/descend 4 steps, 3 cycles) was timed. Physical activity (PA) was assessed using the Kaiser Physical Activity Survey (KPAS; possible range 0–15 points). Sociodemographic and health factors were assessed via self-report. BMI was calculated with measured height and weight. Mixed-effects regression modeled longitudinal change in stair climb performance. Results: Average baseline stair climb time was 18.12 seconds (95% CI: 17.83–18.41), with 0.98% (95% CI: 0.84%–1.11%) annual slowing. In fully adjusted models, higher levels of PA were associated with faster stair climb times (2.09% faster per point higher, 95% CI: −2.87%–1.30%), and black women had 5.22% (95% CI: 2.43%–8.01%) slower performance compared to white women. Smoking, financial strain, diabetes, osteoarthritis, fair/poor health, and stroke were associated with 3.36% (95% CI: 0.07%–6.65%), 7.56% (95% CI: 4.75%–10.37%), 8.40% (95% CI: 2.89%–13.92%), 8.46% (95% CI: 5.12%–11.79%), 9.16% (95% CI: 4.72%–13.60%), and 16.94% (95% CI: 5.37%–28.51%) slower performance, respectively. In separate models, higher BMI (per 1-unit), osteoarthritis, fair/poor health, and diabetes, were each associated with 0.06% (95% CI:0.04%–0.08%), 0.48% (95% CI:0.12%–0.84%), 0.81% (95% CI:0.35%–1.28%), and 0.84% (95% CI:0.22%–1.46%), additional slowing per year over time. Conclusion: Significant declines in function were evident as women transitioned from midlife to early late life. Declines were amplified by indicators of poor health, emphasizing the importance of health in midlife for promoting healthy aging.