Data Sheet 1_Associations of spirometric z-scores with mobility, endurance-related performance, and functional lower-limb strength in community-dwelling older adults: a cross-sectional study.docx

The primary exposures were z-scores for forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), and FEV₁/FVC. Mobility was assessed using the Timed Up and Go (TUG) test and 4-m gait speed; endurance-related performance was assessed using the 2-min step test (2MST); overall physical function was assessed using the Short Physical Performance Battery (SPPB); and functional lower-limb strength was explored using the 30-s chair stand and the five-times sit-to-stand test.

Spearman rank correlation and multivariable linear regression were used, with adjustment for age, sex, body mass index (BMI), smoking status, and number of comorbidities.</p>Results<p>The mean age of the participants was 68.22 ± 5.75 years, and 80.9% were female. After adjustment for age, sex, BMI, smoking status, and number of comorbidities, each 1-unit increase in the FEV₁ and FVC z-scores was associated with a 0.162-s shorter TUG time (β = −0.162, 95% CI: −0.297 to −0.028) and a 0.167-s shorter TUG time (β = −0.167, 95% CI: −0.306 to −0.028), respectively.

Each 1-unit increase in the FVC z-score was also associated with 3.605 more repetitions in the 2MST (β = 3.605, 95% CI: 1.297–5.913) and 1.143 more repetitions in the 30-s chair stand (β = 1.143, 95% CI: 0.568–1.718). The FEV₁/FVC z-score was not significantly associated with any core physical performance outcome. In the LLN-based analysis, participants with FVC below the LLN had a 0.461-s longer TUG time (β = 0.461, 95% CI: 0.061–0.861), completed 7.966 fewer repetitions in the 2MST (β = −7.966, 95% CI: −14.671 to −1.262), and completed 2.818 fewer repetitions in the 30-s chair stand (β = −2.818, 95% CI: −4.493 to −1.143) than those with FVC at or above the LLN.

FEV₁/FVC below the LLN was not significantly associated with any core physical performance outcome. After outcome-specific false discovery rate correction, the associations of FEV₁ and FVC z-scores with TUG time (both q = 0.029) and of FVC z-score with 2MST performance (q = 0.006) remained statistically significant.</p>Conclusion<p>Among community-dwelling older adults, spirometric z-scores—particularly the FVC z-score—were associated with mobility, endurance-related performance, and functional lower-limb strength.

The consistent results obtained using continuous FVC z-scores and LLN-based classification suggest that FVC may provide complementary information when evaluating physical function. These findings should be confirmed in larger, multicenter longitudinal studies. From a public health perspective, standardized spirometry may complement brief physical-performance tests in community health assessments by helping to characterize older adults with concurrent respiratory and functional vulnerability.

Longitudinal and intervention studies are needed to determine whether lower FVC predicts functional decline and whether respiratory muscle training, multicomponent exercise, or combined programs can preserve mobility and independence in later life.</p>