Relationship between upper and lower limb function, cognitive impairment, and depression in patients with chronic...

Chronic obstructive pulmonary disease (COPD) often coexists with limb dysfunction, cognitive decline, and depression. The 20-item Upper Extremity Functional Index (UEFI) and Lower Extremity Functional Index (LEFI) (each 0-80, higher = better) are COPD-specific, yet their links to cognition and mood remain untested. We assessed whether UEFI and LEFI independently predict cognitive impairment and clinically significant depressive symptoms. In this single-center cross-sectional study (January 2021-January 2023), 120 stable out-patients aged ≥40 years with spirometry-confirmed COPD and without confounding neuromuscular disorders were enrolled. Upper and lower limb functions were assessed using the UEFI and LEFI, respectively. Cognitive impairment was defined as a Montreal Cognitive Assessment score < 26; moderate-to-severe depression as a Patient Health Questionnaire-9 score ≥ 10. Both instruments are validated in COPD. Multivariable logistic regression adjusted for age, sex, body mass index, smoking status, forced expiratory volume in 1 second/forced vital capacity ratio, and global initiative for chronic obstructive lung disease stage. Participants (mean age 65.2 ± 7.8 years; 58.3% male) included 35.8% with depression and 29.2% with cognitive impairment. Each 1-standard deviation increase in UEFI reduced the odds of cognitive impairment (adjusted odds ratio: 0.46; 95% confidence interval [CI] 0.31-0.70) and depression (odds ratio: 0.48; 95% CI: 0.30-0.76); corresponding LEFI estimates were 0.65 (95% CI: 0.47-0.90) and 0.51 (95% CI: 0.35-0.74). Associations persisted across sensitivity analyses. Poor self-reported limb function independently predicts cognitive decline and depression in COPD. Incorporating UEFI/LEFI into routine assessment may enable early detection and guide integrated rehabilitation.