Smoking Behavior Changes in the Early Rheumatoid Arthritis Period and Risk of Mortality During Thirty-Six Years of Prospective Followup

Abstract

Objective: To investigate whether rheumatoid arthritis (RA) diagnosis influences smoking behavior changes and whether these changes were associated with mortality.

Methods: We identified an incident RA cohort in the Nurses' Health Study (NHS; 1976-2012). Behavioral data were collected through biennial questionnaires. We created a comparison cohort, matching RA cases to women without RA by age and calendar year at the index date of RA diagnosis. To investigate smoking behavior changes in the early RA period, sustained cessation was defined as permanently quitting within 4 years of the RA/index date. We used Cox regression to obtain hazard ratios (HRs) for mortality, comparing sustained smoking cessation to continued smoking.

Results: Among 121,700 women in the NHS, we identified 938 with incident RA matched to 8,951 non-RA comparators. Among current smokers, 40.0% with RA permanently quit smoking in the early RA period, compared to 36.1% of comparators (odds ratio for sustained cessation 1.18 [95% confidence interval (95% CI) 0.88, 1.58]). There were 313 deaths (33.4%) in the RA cohort and 2,042 (22.8%) among comparators. Compared to continued smoking, sustained cessation was associated with similarly decreased mortality in both the RA (HR 0.58 [95% CI 0.33, 1.01]) and comparison (HR 0.47 [95% CI 0.39, 0.58]) cohorts. Women with RA had higher mortality for >5 post-RA pack-years (HR 3.67 [95% CI 2.80, 4.81]) than comparators with >5 post-index pack-years (HR 1.88 [95% CI 1.62, 2.17]; P < 0.001 for interaction; reference: ever-smoker non-RA women with 0 post-index pack-years).

Conclusion: Sustained smoking cessation within 4 years of RA diagnosis reduced mortality risk, with a similar effect observed among non-RA comparators. Smoking >5 pack-years after RA diagnosis significantly increased mortality beyond the risk of non-RA comparators.

Figure 1

Schematic illustrating definitions of smoking behaviors according to the period for smoking cessation around rheumatoid arthritis diagnosis or matched index date. Wedges indicate questionnaire cycles during follow-up in the Nurses’ Health Study. C, current smoker at questionnaire; N, never smoker at questionnaire; P, past smoker at questionnaire; RA, rheumatoid arthritis.

Figure 2

Among ever smokers, multivariable adjusted hazard ratios for total mortality according to cumulative smoking pack-years after RA diagnosis/index date for RA cases and comparators combined into a single analysis (n=5,511).