Association between occupational exposure to mineral oil and rheumatoid arthritis: results from the Swedish EIRA case–control study

Table 3 Relative risk for RA with different combinations of mineral oil exposure and shared epitope genes

Outcome	Exposure to mineral oil	No shared epitope			Any shared epitope
		Cases/controls (n)^a	Relative risk^b	95% confidence interval	Cases/controls (n)^a	Relative risk^b	95% confidence interval
RF⁺ RA	No	28/89	1.0^c		128/88	4.7	2.8–8.0
	Yes	17/43	1.2	0.6–2.5	73/38	6.4	3.4–11.8
RF^- RA	No	32/89	1.0^c		63/88	2.1	1.2–3.6
	Yes	10/43	0.7	0.3–1.5	25/38	2.1	1.1–4.2
Total RA	No	60/89	1.0^c		191/88	3.2	2.1–4.9
	Yes	27/43	0.9	0.5–1.7	98/38	3.9	2.3–6.6
Anti-CP⁺ RA	No	18/89	1.0^c		126/88	8.0	4.4–14.7
	Yes	13/43	1.6	0.7–3.7	75/38	11.1	5.6–22.1
Anti-CP^- RA	No	42/89	1.0^c		65/88	1.5	0.9–2.5
	Yes	14/43	0.7	0.3–1.5	23/38	1.5	0.7–2.9
Total RA	No	60/89	1.0^c		191/88	3.2	2.1–4.9
	Yes	27/43	0.9	0.5–1.7	98/38	3.9	2.3–6.6

Relative risk and 95% confidence interval for developing rheumatoid factor (RF)-positive rheumatoid arthritis (RA), RF^- RA, antibodies to citrulline-containing peptides (anti-CP)-positive RA, anti-CP^- RA and total RA for men with different combinations of exposure to mineral oil and shared epitope genes compared with men unexposed to any mineral oil and lacking shared epitope genes.
^aData on the shared epitope are missing for 10 cases and 51 controls exposed to mineral oil, and for 21 cases and 176 controls unexposed to mineral oil (in comparison with Tables 1 and 2).
^bRelative risk adjusted for age, residential area and smoking.
^cReference group.

ISSN: 1478-6362