Smoking is a Risk Factor for Autoimmune Hepatitis: An English Registry-Based Case–Control Study

Purpose: Smoking is a risk factor for some autoimmune diseases, but its association with autoimmune hepatitis remains unknown. We conducted a population-based matched case–control study to examine the association between tobacco smoking and the risk of autoimmune hepatitis in England.
Patients and Methods: From the Clinical Practice Research Datalink and linked Hospital Episode Statistics, 2005– 2017, we included 987 cases diagnosed with autoimmune hepatitis after age 18 years and up to 10 frequency-matched population controls per case. We used multiple logistic regression to estimate the odds ratio of autoimmune hepatitis in ever-smokers vs never-smokers, adjusting for sex, age, general practice, calendar time of registration with the general practice, and socioeconomic status.
Results: The autoimmune hepatitis cases were more likely to be ever-smokers than the controls (44% vs 37%). The ever-smokers had an increased risk of autoimmune hepatitis compared with the never-smokers (adjusted odds ratio = 1.20, 95% confidence interval 1.03– 1.39).
Conclusion: Smoking was associated with an increased risk of autoimmune hepatitis.

Plain Language Summary: Autoimmune hepatitis is a chronic liver disease associated with genetic variants and environmental exposures, but the causes of autoimmune hepatitis remain unknown. Using registry data, we evaluated the association between tobacco smoking and the risk for autoimmune hepatitis. We found that tobacco smoking was associated with an increased risk of autoimmune hepatitis.

Keywords: epidemiology, chronic hepatitis, risk factors, tobacco