Table 2.

Linear Models of SGRQ Total Score Among Participants With COPD in the COPDGene Study, Ages 50 to 80 Years (n = 4,097)

Variable	β (95% CI)
Age,a y
< 65	Reference
≥ 65	−3.0 (−3.9 to −2.0)
Interaction age × dyspneab
Effect of severe dyspnea if age < 65 y	24.6 (23.2-25.9)
Effect of severe dyspnea if age ≥ 65 y	21.0 (19.6-22.3)
Mean score difference by age when dyspnea is severe	−4.4 (−5.5 to −3.2)
Demographic factors
Sex
Male	Reference
Female	−0.3 (−1.2 to 0.6)
Race
Non-Hispanic white	Reference
African American	3.0 (1.9-4.1)
Smoking status
Past smoker	Reference
Current smoker	2.3 (1.3-3.2)
BMI
< 30	Reference
≥ 30	2.2 (1.2-3.2)
Respiratory factors
mMRC dyspnea scorec
< 2	Reference
≥ 2	22.8 (21.8-23.9)
Chronic bronchitis
No	Reference
Yes	9.6 (8.5-10.6)
Frequent exacerbations
No (< 2/y)	Reference
Yes (≥ 2/y)	6.8 (5.6-8.0)

Models additionally were adjusted for FEV₁ % predicted, time with a COPD diagnosis, and comorbidities. COPDGene = Genetic Epidemiology of COPD; mMRC = modified Medical Research Council; SGRQ = St. George’s Respiratory Questionnaire.

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

^bP < .001.

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