Low balance confidence in relation to strength training, walking, sitting, and physical function among women aged 75–105 years: a cross-sectional study within the Women’s Health Initiative Strong and Healthy (WHISH) Intervention Cohort

Falls are the leading cause of injury and injury death among older women in the United States. We examined associations of low balance confidence, defined as an Activities-specific Balance Confidence (ABC) Scale score < 67%, with strength training, walking, sitting time, and physical function (PF) among women aged ≥ 75 years in the Women’s Health Initiative Strong and Healthy ( WHISH ) trial. We analyzed cross-sectional data from 8,916 women aged 75–105 years assigned to the WHISH physical activity intervention. Participants self-reported their weekly participation in strength training, walking, daily sitting time, and PF. Balance confidence was measured using the ABC scale. Low balance confidence was defined as an ABC score < 67% and examined in the total cohort and separately among women aged 75–84 and ≥ 85 years. Cross-sectional associations with strength training, walking, sitting time, and PF were estimated using analysis of variance (ANOVA), chi-squared tests, and modified Poisson regression with robust variance. Regression models estimated prevalence ratios (PRs) and 95% confidence intervals (CIs) and were adjusted for age, education, body mass index (BMI), and race/ethnicity. Mean age was 84.9 years, with 47.3% of participants aged ≥ 85 years. The prevalence of low balance confidence was 35.1% overall, 23.9% among women aged 75–84 years, and 47.6% among women aged ≥ 85 years. Strength training ≥ 2 h per week was associated with a 24% lower prevalence of low balance confidence (PR = 0.76, 95% CI: 0.71–0.81); walking ≥ 4.25 h/week with a 59% lower prevalence of low balance confidence (PR = 0.41, 95% CI: 0.37–0.45); while sitting ≥ 8 h/day was associated with a 24% higher prevalence of low balance confidence (PR = 1.24, 95% CI: 1.17–1.32). High PF (score ≥ 90) was associated with an 88% lower prevalence of low balance confidence (PR = 0.12, 95% CI: 0.10–0.14; p < 0.0001). More strength training and walking, lower sitting time, and higher PF were strongly associated with lower prevalence of low balance confidence among women aged ≥ 75 years. Although these associations were more pronounced among women aged 75–84 years, they were also observed for women aged ≥ 85 years. Longitudinal studies are needed to establish temporality.