Table 4.

Hazard ratios for incident asthma after blood draw date, comparing women with RA to their matched controls in the Nurses’ Health Studies (n=951).

	Incident asthma cases/person-years	HR (95%CI) controlling for matching factors*	Multivariable** HR (95%CI)
Pre-RA ACPA+ (n=49)	8/890	1.71 (0.72, 4.07)	1.74 (0.72, 4.24)
Matched controls (n=136)	14/2,660	1.00 (Ref)	1.00 (Ref)
Pre-RA ACPA− (n=203)	31/3,777	1.73 (1.11, 2.70)	1.62 (1.04, 2.55)
Matched controls (n=563)	52/11,039	1.00 (Ref)	1.00 (Ref)
All pre-RA (n=252)	39/4,667	1.72 (1.16, 2.56)	1.65 (1.11, 2.46)
Matched controls (n=699)	66/13,698	1.00 (Ref)	1.00 (Ref)

P for pre-RA/control status-ACPA status interaction in unadjusted analysis: 0.20

P for pre-RA/control status-ACPA status interaction in adjusted analysis: 0.23

^*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), and median household income (quartile).

ACPA, anti-citrullinated protein antibodies; CI, confidence interval; HR, hazard ratio; RA, rheumatoid arthritis.