Table 3

ORs with 95% CI of developing rheumatoid arthritis (RA) for subjects who reported past exposure to permanent night shift work compared with those who had never been exposed, by duration (years) and intensity (nights/months) of night shift work

ACPA-positive RA				ACPA-negative RA
Duration	ca/co*	OR (95% CI)†	p Value	ca/co*	OR (95% CI)†	p Value
0	828/1537	1.0 (reference)		514/1537	1.0 (reference)
<5 years	149/275	0.8 (0.6 to 1.0)	0.06	81/275	0.9 (0.7 to 1.2)	0.5
5–10 years	45/89	0.7 (5.1 to 1.1)	0.1	24/89	0.8 (0.5 to 1.3)	0.4
>10 years	65/152	0.6 (0.4 to 0.9)	0.005	35/152	0.7 (0.4 to 1.0)	0.06
p for trend			0.002			0.04
Intensity	ca/co*	OR (95% CI)†	p	ca/co*	OR (95% CI)†	p
0	828/1537	1.0 (reference)		514/1537	1.0 (reference)
<10 nights/months	184/362	0.8 (0.6 to 1.0)	0.02	97/362	0.8 (0.6 to 1.1)	0.1
>10 nights/months	75/154	0.7 (0.5 to 1.0)	0.03	43/154	0.8 (0.6 to 1.2)	0.4
p for trend			0.007			0.2

*Number of exposed cases and controls.
†Adjusted for age, gender, residential area, ancestry, smoking, educational level and shift work.
ACPA, anticitrullinated peptide antibodies.