Table 1.
Baseline characteristics of population based Swedish cohorts used to study squamous cell cancer* and matched general population comparators, and basal cell cancer† and matched general population comparators. Values are numbers (percentages) unless stated otherwise
| Characteristics | Squamous cell cancer | Basal cell cancer | |||||
|---|---|---|---|---|---|---|---|
| TNF inhibitor treated (n=12 558) | Biologics-naive RA (n=46 409) | General population (n=379 666) | TNF inhibitor treated (n=8827) | Biologics-naive RA (n=43 675) | General population (n=364 584) | ||
| Female sex | 9473 (75.4) | 33 202 (71.5) | 270 623 (71.3) | 6601 (74.8) | 31 216 (71.5) | 259 816 (71.3) | |
| Mean (SD) age at entry, years | 55.2 (13.3) | 60.9 (14.7) | 59.4 (14.7) | 55.3 (13.6) | 61.6 (14.7) | 60.8 (14.5) | |
| Entry year, median | 2006 | 2004 | 2004 | 2008 | 2005 | 2005 | |
| Mean (SD) follow-up, years | 5.9 (3.8) | 5.1 (3.6) | 6.5 (3.7) | 4.2 (2.7) | 4.7 (3.1) | 5.8 (3.0) | |
| Country of birth: | |||||||
| Nordic | 11 774 (93.8) | 43 603 (94.0) | 348 551 (91.8) | 8232 (93.3) | 41 013 (93.9) | 333 155 (91.4) | |
| Other (including missing) | 784 (6.2) | 2806 (6.0) | 31 115 (8.2) | 595 (6.7) | 2662 (6.1) | 31 429 (8.6) | |
| ≤9 years’ education | 3824 (30.5) | 20 009 (43.1) | 140 142 (36.9) | 2456 (27.8) | 18 456 (42.3) | 126 021 (34.6) | |
| Comorbidities before start of follow-up: | |||||||
| Chronic obstructive pulmonary disease | 302 (2.4) | 1581 (3.4) | 6627 (1.8) | 233 (2.6) | 1687 (3.9) | 6650 (1.8) | |
| Diabetes mellitus | 679 (5.4) | 2857 (6.2) | 16 239 (4.3) | 507 (5.7) | 2934 (6.7) | 16 329 (4.5) | |
| Ischaemic heart disease | 705 (5.6) | 4493 (9.7) | 26 832 (7.1) | 495 (5.6) | 4571 (10.5) | 25 892 (7.1) | |
| Joint surgery | 3267 (26.0) | 8277 (17.8) | 17 588 (4.6) | 1964 (22.2) | 8292 (19.0) | 17 442 (4.8) | |
| Dysplastic naevi | 115 (0.9) | 276 (0.6) | 2007 (0.5) | 93 (1.1) | 333 (0.8) | 1913 (0.5) | |
| Any benign skin disease‡ | 660 (5.3) | 1748 (3.8) | 11 247 (3.0) | 606 (6.9) | 2084 (4.8) | 12 248 (3.4) | |
| Squamous cell cancer | 0 (0) | 0 (0) | 0 (0) | 49 (0.6) | 494 (1.1) | 726 (0.2) | |
RA=rheumatoid arthritis; TNF=tumour necrosis factor.
*RA patients starting TNF inhibitor as first ever biologic drug 1998-2012; RA patients identified 2001-12 (censored at start of first biologic drug).
†RA patients starting TNF inhibitor as first ever biologic drug 2004-12; RA patients identified 2001-12 (start of follow-up earliest 1 January 2004, censored at start of first biologic drug).
‡Excluding actinic keratosis.