Table 3.

Hazard ratios for incident COPD after blood draw date and before date of RA diagnosis (or matched date for matched controls), comparing women with RA to their matched controls in the Nurses’ Health Studies (n=1,125).

	Incident COPD cases/person-years	HR (95%CI) controlling for matching factors*	Multivariable** HR (95%CI)
Pre-RA ACPA+ (n=59)	6/357	18.49 (2.22, 153.71)	10.84 (1.13, 104.08)
Matched controls (n=176)	1/1,115	1.00 (Ref)	1.00 (Ref)
Pre-RA ACPA− (n=224)	19/2,251	2.22 (1.23, 4.02)	1.94 (1.06, 3.54)
Matched controls (n=666)	26/6,854	1.00 (Ref)	1.00 (Ref)
All pre-RA (n=283)	25/2,608	2.82 (1.64, 4.87)	2.33 (1.34, 4.04)
Matched controls (n=842)	27/7,969	1.00 (Ref)	1.00 (Ref)

P for pre-RA/control status-ACPA status interaction in unadjusted analysis: 0.54

P for pre-RA/control status-ACPA status interaction in adjusted analysis: 0.16

^*Each woman with RA was matched to 3 controls by age, time from blood draw to index date, cohort, calendar year, fasting status/time of day at blood draw, menopausal status, and postmenopausal hormone use.

^**Additionally adjusted for smoking (continuous pack-years), body mass index (continuous, kg/m²), median household income (quartile), and asthma (yes/no).

ACPA, anti-citrullinated protein antibodies; CI, confidence interval; COPD, chronic obstructive pulmonary disease; HR, hazard ratio; RA, rheumatoid arthritis.