Table 4.

Association between cigarette smoking in pack-years and risk of incident SLE among participants in Nurses’ Health Study and Nurses’ Health Study II, overall and by anti-double stranded DNA (dsDNA) antibody status

	Pack-years
	Never smoker	>0 to ≤10	>10	p-trend
Overall SLE
Cases/Person-Years	148/3,074,178	52/1,032,876	86/1,535,233
Age-Adjusted HR (95%CI)a	1.00 (ref)	1.03 (0.75–1.41)	1.16 (0.88–1.54)	0.28
Alcohol-Adjusted HR (95%CI)b	1.00 (ref)	1.11 (0.81–1.54)	1.27 (0.96–1.68)	0.10
Multivariable-Adjusted HR (95%CI)c	1.00 (ref)	1.09 (0.79–1.51)	1.22 (0.92–1.61)	0.18
dsDNA+ SLE
Cases/Person-Years	56/3,073,263	24/1,032,491	41/1,534,731
Age-Adjusted HR (95%CI)a	1.00 (ref)	1.27 (0.78–2.05)	1.57 (1.04–2.39)	0.04
Alcohol-Adjusted HR (95%CI)b	1.00 (ref)	1.35 (0.83–2.20)	1.68 (1.10–2.58)	0.02
Multivariable-Adjusted HR (95%CI)c	1.00 (ref)	1.32 (0.81–2.16)	1.60 (1.04–2.45)	0.04
dsDNA− SLE
Cases/Person-Years	92/3,073,468	28/1,032,494	45/1,534,739
Age-Adjusted HR (95%CI)a	1.00 (ref)	0.88 (0.57–1.35)	0.93 (0.64–1.35)	0.75
Alcohol-Adjusted HR (95%CI)b	1.00 (ref)	0.97 (0.63–1.49)	1.03 (0.70–1.50)	0.87
Multivariable-Adjusted HR (95%CI)c	1.00 (ref)	0.94 (0.61–1.46)	0.98 (0.67–1.44)	0.96

p for heterogeneity between the cohorts >0.05 for all analyses

^aAdjusted for age (months), questionnaire cycle, cohort

^bAdditionally adjusted for alcohol intake

^cAdditionally adjusted for race, early menarche, oral contraceptive use body mass index, zip code-level median household income from U.S. census.

HR = hazard ratio; CI = confidence interval, g/day=grams per day, dsDNA+ = double stranded DNA positive, dsDNA− = double stranded DNA negative