Table 3.

Linear Models of SGRQ Total Score Among Participants With COPD in SPIROMICS, Ages 50 to 80 Years (n = 1,522)

Variable	β (95% CI)
Age,a y
< 65	Reference
≥ 65	−4.2 (−5.7 to −2.6)
Interaction age × dyspneab
Effect of severe dyspnea if age < 65 y	16.9 (14.6-19.2)
Effect of severe dyspnea if age ≥ 65 y	13.9 (11.7-16.0)
Mean score difference by age when dyspnea is severe	−6.2 (−8.7 to −3.7)
Demographic factors
Sex
Male	Reference
Female	1.5 (0.0-3.0)
Race
Non-Hispanic white	Reference
African American	1.7 (−0.5 to 3.8)
Smoking status
Past smoker	Reference
Current smoker	3.4 (1.8-5.0)
BMI
< 30	Reference
≥ 30	3.5 (1.9-5.0)
Respiratory factors
mMRC dyspnea scorec
< 2	Reference
≥ 2	15.3 (13.6-16.9)
Chronic bronchitis
No	Reference
Yes	6.1 (4.4-7.9)
Frequent exacerbations
No (< 2/y)	Reference
Yes (≥ 2/y)	6.3 (4.2-8.4)

Models additionally were adjusted for FEV₁ % predicted and comorbidities. mMRC = modified Medical Research Council; SGRQ = St. George’s Respiratory Questionnaire; SPIROMICS = Subpopulations and Intermediate Outcome Measures in COPD Study.

^aEffect of age unweighted average over both levels of dyspnea.

^bP = .04.

^cEffect of severe dyspnea unweighted average over both groups of age.