Table 2.

Association between periodontal diagnostic codes and smoking habits compared with never smokers in EIRA RA cases, in relation to double seropositive or negative antibody status and gender*

Smoking habits		ACPA-positive and RF-positive RA (n=1261)		ACPA-negative and RF-negative RA (n=616)
		No with periodontitis (%)†	OR (95% CI)‡	No with periodontitis (%)†	OR (95% CI)‡
Total
	All	667 (100)		328 (100)
	Women	479 (100)		234 (100)
	Men	188 (100)		94 (100)
Never smokers
	All	162 (24.3)	1.0 (ref)	122 (37.2)	1.0 (ref)
	Women	130 (27.1)	1.0 (ref)	90 (38.5)	1.0 (ref)
	Men	32 (17.0)	1.0 (ref)	32 (34.0)	1.0 (ref)
Ex-smokers
	All	254 (38.1)	1.8 (1.4 to 2.3)§	94 (28.7)	0.8 (0.6 to 1.1)
	Women	178 (37.2)	1.9 (1.4 to 2.5)§	53 (22.6)	0.8 (0.5 to 1.2)
	Men	76 (40.4)	1.9 (1.1 to 3.4)§	41 (43.6)	0.7 (0.4 to 1.3)
Ever smokers
	All	505 (75.7)	1.7 (1.4 to 2.1)§	206 (62.8)	1.0 (0.7 to 1.2)
	Women	349 (72.9)	1.7 (1.3 to 2.2)§	144 (61.5)	1.1 (0.8 to 1.5)
	Men	156 (83.0)	2.0 (1.2 to 3.3)§	62 (66.0)	0.7 (0.4 to 1.1)
Current smokers
	All	200 (30.0)	2.0 (1.5 to 2.7)§	76 (23.2)	1.0 (0.7 to 1.5)
	Women	133 (27.8)	1.8 (1.3 to 2.5)§	61 (26.1)	1.3 (0.8 to 1.9)
	Men	67 (35.6)	3.3 (1.8 to 6.2)§	15 (16.0)	0.5 (0.2 to 1.1)

*The periodontal diagnostic codes include periodontitis, peri-implantitis and increased risk for periodontitis/peri-implantitis.

†Number (%) of ACPA-positive and RF-positive or ACPA-negative and RF-negative RA cases with periodontal diagnostic codes.

‡ORs, with a 95% CI, were adjusted for age, gender, education and residential area.

§p <0.05 for association between periodontal diagnostic codes and smoking habits as compared to never smokers among ACPA-positive and RF-positive or ACPA-negative and RF-negative RA cases.

ACPA, anticitrullinated protein antibody; EIRA, Epidemiological Investigation of Rheumatoid Arthritis; RA, rheumatoid arthritis; ref, reference group; RF, rheumatoid factor.