Table 1.

Selected studies showing an association between cigarette smoking and Rheumatoid Arthritis (RA) risk.

Exposure	First Author	Study type	Cohort	Outcome	Risk of exposure	# RA cases	Reference
Cigarette Smoking	Di Giuseppe	Meta-analysis (3 prospective cohorts, 7 case-control)	Multiple	RF +/- RA	Ever smoking: RF+ RA RR 2.47, RF- RA RR 1.58	4552	(28)
Cigarette Smoking	Hedstrom	Case-Control	Sweden (EIRA)	ACPA +/- RA	Ever smoking: ACPA+ RA OR 1.9, ACPA- RA OR 1.3	3655	(29)
Cigarette Smoking	Too	Case-Control	Malaysia (MyEIRA)	ACPA +/- RA	Ever smoking: ACPA+ RA OR 4.1	1076	(30)
Cigarette Smoking	Bang	Case-Control	Korea	RA	Ever smoking: RA OR 2.7	1482	(31)
Cigarette Smoking	Pederson	Case-Control	Denmark	ACPA +/- RA	Ever smoking: ACPA+ RA OR 1.22 to 57.4; stratified by pack-year exposure AND SE+/-	515	(32)
Cigarette Smoking	Kochi	Case-Control	Japan	RA	Ever smoking: RA OR 1.15 to 1.35	2015	(33)
Cigarette Smoking	Karlson	Retrospective Cohort	USA (Women’s Health Cohort)	RA	Ever smoking: RA RR 1.10 to 1.32; stratified by pack-year	7697	(25)
Cigarette Smoking	Costenbader	Retrospective Cohort	USA (Nurses Health Study)	RA	Ever smoking: RA RR 1.47	680	(26)
Cigarette Smoking	Di Giuseppe	Retrospective Cohort	Sweden (Swedish Mammography Cohort)	RA	Ever smoking: RA RR 2.31	219	(27)
Cigarette Smoking	de Hair	Prospective Cohort	Netherlands (IgM RF or ACPA + at-risk)	RA	Ever smoking: Sero+ RA HR 9.6	15	(34)
Cigarette Smoking	Ponchel	Prospective Cohort	United Kingdom (Leeds; RF or ACPA+ with joint pain)	RA	Ever smoking: Sero+ RA OR 3.1	125	(35)

ACPA, anti-citrullinated protein antibodies; RF, Rheumatoid Factor; EIRA, Epidemiological Investigation of Rheumatoid Arthritis; RR, Relative Risk; OR, Odds Ratio; HR, Hazards Ratio. All RR/OR/HR are statistically significant unless otherwise stated.