Table 2.

Demographic and clinical characteristics of rheumatoid arthritis (RA) and control cohorts^*

	Patients with RA (N=582)	Subjects without RA (N=603)	p value
Age at RA diagnosis/index date, mean ± SD in years	57.7 ± 15.1	58.2 ± 15.2	0.58
Years of follow up, mean ± SD	16.4 ± 10.5	19.3 ± 11.1	--
Female, N (%)	427 (73.4%)	441 (73.1%)	0.93
Smoking status at baseline, N (%)
Current smoker	164 (28.2%)	144 (23.9%)	<0.01
Former smoker	144 (24.7%)	118 (19.6%)
Chest X-ray documented, N (%)	230 (39.5%)	352 (58.4%)	<0.01
Fibrotic changes on chest X-ray, N (%)	157 (27.0%)	154 (25.5%)	0.57
PFT documented, N (%)	111 (19.1%)	104 (17.2%)	0.42
PFT restrictive pattern (TLC ≤ 80% predicted), N (%)	27 (4.6%)	11 (1.8%)	<0.01
CT documented, N (%)	78 (13.4%)	85 (14.1%)	0.73
CT reported presence of parenchymal disease, N (%)	38 (6.5%)	24 (4.0%)	0.05

^*Except where indicated otherwise, values are the number (%) of patients.

RA = rheumatoid arthritis; SD = standard deviation; PFT = pulmonary function test; TLC = total lung capacity; CT = computed tomography