Table 3.

Dichotomization of FEV₁ % predicted subgroups into high and low COPD Severity Scores: Examining the association of COPD severity with depressive symptoms within each strata of FEV₁

	OR* (95% CI) for Depressive Symptoms†
	Subgroup Median COPD Severity Score‡	Low COPD Severity Score (< Subgroup Median)	High COPD Severity Score (≥ Subgroup Median)	p-value for OR difference within FEV1 subgroup§
COPD subjects
FEV1 ≥80% predicted	7	1.8 (0.9 – 3.8)	4.3 (2.3 – 8.0)	p=0.009
FEV1 ≥50–80% predicted	9	2.0 (1.1 – 3.7)	4.0 (2.2 – 7.2)	p<0.001
FEV1 ≥30–50% predicted	12	2.5 (1.2 – 5.1)	7.4 (3.9 – 14)	p<0.001
FEV1 <30% predicted	15	7.6 (3.4 – 17)	8.3 (3.8 – 18)	p=0.84

^*Odds ratio of depressive symptoms is relative to referent group without COPD. Each FEV₁ stratum was dichotomized based on the median COPD Severity Score within that stratum. Results are from multivariate logistic regression adjusted for age, gender, marital status, race, education, annual household income, body mass index, and all comorbidities listed in Table 1

^†Depressive symptoms defined as geriatric depression score ≥ 6

^‡The COPD Severity Score is a survey-based measure of COPD severity that takes into account respiratory symptoms, COPD medication usage, prior hospitalizations and intubations for COPD, and home oxygen usage. See Methods.

^§Based on likelihood ratio testing. For example, within the subgroup of patients with FEV₁ ≥ 80% predicted, those with a high COPD Severity Score had a significantly higher risk of depressive symptoms relative to referents without COPD (OR=4.3) than those whose COPD Severity Score was low (OR=1.8) (p=0.009 for difference between these two OR’s).