Associations between lung function and physical and cognitive health in the Canadian Longitudinal Study on Aging (CLSA): A cross-sectional study from a multicenter national cohort.

BACKGROUND: Low lung function is associated with high mortality and adverse cardiopulmonary outcomes. Less is known of its association with broader health indices such as self-reported respiratory symptoms, perceived general health, and cognitive and physical performance. The present study seeks to address the association between forced expiratory volume in 1 second (FEV1), an indicator of lung function, with broad markers of general health, relevant to aging trajectory in the general population. METHODS AND FINDINGS: From the Canadian general population, 22,822 adults (58% females, mean age 58.8 years [standard deviation (SD) 9.6]) were enrolled from the community between June 2012 and April 2015 from 11 Canadian cities and 7 provinces. Mixed effects regression was used to assess the cross-sectional relationship between FEV1 with self-reported respiratory symptoms, perceived poor general health, and cognitive and physical performance. All associations were adjusted for age, sex, body mass index (BMI), education, smoking status, and self-reported comorbidities and expressed as adjusted odds ratios (aORs). Based on the Global Lung Function Initiative (GLI) reference values, 38% (n = 8,626) had normal FEV1 (z-scores >0), 37% (n = 8,514) mild (z-score 0 to > -1 SD), 19% (n = 4,353) moderate (z-score -1 to > -2 SD), and 6% (n = 1,329) severely low FEV1 (z-score = < -2 SD). There was a graded association between lower FEV1 with higher aOR [95% CI] of self-reported moderate to severe respiratory symptoms (mild FEV1 1.09 [0.99 to 1.20] p = 0.08, moderate 1.45 [1.28 to 1.63] p < 0.001, and severe 2.67 [2.21 to 3.23] p < 0.001]), perceived poor health (mild 1.07 [0.9 to 1.27] p = 0.45, moderate 1.48 [1.24 to 1.78] p = <0.001, and severe 1.82 [1.42 to 2.33] p < 0.001]), and impaired cognitive performance (mild 1.03 [0.95 to 1.12] p = 0.41, moderate 1.16 [1.04 to 1.28] p < 0.001, and severe 1.40 [1.19 to 1.64] p < 0.001]). Similar graded association was observed between lower FEV1 with lower physical performance on gait speed, Timed Up and Go (TUG) test, standing balance, and handgrip strength. These associations were consistent across different strata by age, sex, tobacco smoking, obstructive, and nonobstructive impairment on spirometry. A limitation of the current study is the observational nature of these findings and that causality cannot be inferred. CONCLUSIONS: We observed graded associations between lower FEV1 with higher odds of disabling respiratory symptoms, perceived poor general health, and lower cognitive and physical performance. These findings support the broader implications of measured lung function on general health and aging trajectory.

Prevalence and burden of COPD misclassification in the Canadian Longitudinal Study on Aging (CLSA).

INTRODUCTION: To examine the prevalence of chronic obstructive pulmonary disease (COPD) misclassification and the associated burden of symptoms, healthcare utilisation and physical performance status in the Canadian general population. This information is presently lacking from large population-based studies with high-quality spirometry data that can be generalised to the general population. METHODS: The prevalence of self-reported physician-diagnosed COPD and the concordance with spirometry airflow obstruction (AO) were assessed in a cross-sectional cohort of Canadian older adults. The associations between confirmed COPD, under-diagnosis and over-diagnosis with self-reported respiratory symptoms, healthcare utilisation and physical performance (timed up and go, handgrip strength and 4 metres walk test) were assessed, adjusting for baseline characteristics using multivariable linear and logistic models. RESULTS: A total of 21 242 participants (mean age 64 (SD 10) years; 42% men) with high quality spirometry were included. Physician-diagnosed COPD was reported in (n=973) 5% of the participants. Only (n=217) 1% of the entire cohort had confirmed COPD supported by spirometry AO. Discordance between self-reported COPD and spirometry findings was observed in (n=1565) 8%: with 4% representing under-diagnosis cases (no self-reported COPD but AO) and 4% representing over-diagnosis cases (self-reported COPD but no AO). Compared with normals (no self-reported COPD and normal spirometry), those with confirmed, under-diagnosed or over-diagnosed COPD showed higher risks for respiratory symptoms (adjusted OR (aOR) 2.1 (95% CI: 1.6 to 2.7); aOR 1.8 (95% CI: 1.6 to 2.1]; aOR 1.6 (95% CI: 1.4 to 1.9)); healthcare utilisation in the prior 12 months (ß coefficient 0.8 (95% CI: 0.2 to 2.6); ß 0.9 (95% CI: 0.5 to 1.5); ß 1.6 (95% CI: 0.7 to 4.0)). Mood disorders were higher in confirmed and over-diagnosed COPD (aOR 1.7 (95% CI: 1.3 to 2.4); 1.7 (95% CI: 1.4 to 2.0), respectively). Physical performance was lower for COPD groups. CONCLUSIONS: The prevalence of COPD misclassification is high in the general population of older adults. These were associated with significantly high burden of respiratory symptoms, healthcare utilisation and low physical performance compared with the general population with normal spirometry and no self-reported COPD. These findings highlight the high burden of COPD misclassification, which may be substantially reduced with greater accessibility to spirometry measurements in the community.