Associations Between Muscle Weakness and Clinical Outcomes in Current and Former Smokers

Introduction: Smokers with chronic obstructive pulmonary disease (COPD) are at increased risk of muscle weakness. There are limited data describing weakness in smokers with normal spirometry and preserved ratio -impaired spirometry (PRISm), 2 subgroups at risk of respiratory symptom burden and activity limitations. In this study, we evaluated the associations of 2 weakness measures, sit -to -stand (STS) and handgrip strength (HGS), with clinical outcomes in smokers with COPD, normal spirometry, and PRISm.Methods: We evaluated 1972 current and former smokers from the COPD Genetic Epidemiology (COPDGene (R)) cohort with STS and HGS measurements at their 10 -year study visit. Multivariable regression modeling was used to assess associations between weakness measures and the 6 -minute walk distance (6MWD) test, the St George's Respiratory Questionnaire (SGRQ), the Short -Form -36 (SF -36), severe exacerbations, and prospective mortality, reported as standardized coefficients (13), odds ratios (ORs), or hazard ratios (HRs).Results: Compared with HGS, STS was more strongly associated with the 6MWD (13=0.45, p<0.001 versus. 13=0.25, p<0.001), SGRQ (13=-0.24, p<0.001 versus 13=-0.18, p<0.001), SF -36 Physical Functioning (13=0.36, p<0.001 versus 13=0.25, p<0.001), severe exacerbations (OR 0.95, p=0.04 versus OR 0.97, p=0.01), and prospective mortality (HR 0.83, p=0.001 versus HR 0.94, p=0.03). Correlations remained after stratification by spirometric subgroups. Compared with males, females had larger magnitude effect sizes between STS and clinical outcomes.Conclusion: STS and HGS are easy to perform weakness measures that provide important information about functional performance, health -related quality of life, severe exacerbations, and survival in smokers, regardless of spirometric subgroup. This iterates the importance of screening current and former smokers for weakness in the outpatient setting.