Table 1.

Characteristics of lung cancer cases versus cancer-free SLE subjects

Variables	Lung Cancer Cases (n = 49)	Cancer-free (n = 4,938)
Mean age (in years) at cohort entry	51.2 (47.3, 55.1)*	38.2 (37.8, 38.6)
Percent male	20.4 (10.2, 34.3)	9.2 (8.4, 10)
Percent white	84.8 (71.1, 93.7)	61.8 (60.4, 63.1)
Mean disease duration at entry, in years	5.4 (3.0, 7.7)	6 (5.7, 6.2)
Percent ever smoking at cohort entry	84.2 (68.7, 94)	40.1 (38.7, 41.5)
Mean pack-years at entry (in smokers)**	28.2 (11.1, 45.2)	11.6 (10.6, 12.6)
Percent positive for dsDNA at cohort entry	16.7 (7, 31.4)	27.1 (25.9, 28.4)
Percent with high disease activity at cohort entry***	59 (42.1, 74.4)	40.8 (39.4, 42.3)
Percent with pulmonary fibrosis at entry****	0 (0, 9.7)*	1.7 (1.4, 2.2)

^*Brackets indicate 95% confidence intervals (CIs) aside from pulmonary fibrosis, where since none of the cancer cases had pulmonary fibrosis at entry, we only have uncertainty on one side of the interval, hence we have a one-sided 97.5% interval, rather than a 95% CI.

^**A sub-analysis was also performed for 6 centers where more precise, time-dependent data on smoking exposure had been collected: Sweden, San Francisco, Montreal, Halifax, Toronto and Winnipeg. Those analyses included 11 cases of lung cancer and 724 cancer-free subjects.

^***Except in one center (UCSF) where self-report items were used, SLE activity was assessed by the mean adjusted SLE disease activity index (SLEDAI-2K), and categorized within quartiles over the full observation period.

^****Pulmonary fibrosis was assessed by the relevant item on the SLICC/ACR Damage Index.