https://orcid.org/0000-0003-0626-179X
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Abstract
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.
Abbreviations
AIH, Autoimmune hepatitis; CPRD, clinical practice research datalink; CI, confidence interval; GWAS, Genome-wide association studies; HES, hospital episode statistics; HLA, human leucocyte antigen; ICD-10, international classification of diseases 10th edition; IMD, index of multiple deprivation; OR, odds ratio; PBC, primary biliary cholangitis; PSC, primary sclerosing cholangitis.
Permission to Reproduce Material from Other Sources
This study is based in part on data from the Clinical Practice Research Datalink (CPRD) obtained under the University of Nottingham licence from the United Kingdom Medicines and Healthcare Products Regulatory Agency. All data were reused with permission, and we extracted the dataset under this license. The anonymised data is provided by patients and collected by the NHS as part of their care and support. The interpretation and conclusion contained in this study are those of the authors alone. Hospital Episode Statistics Data copyright® (2015) was reused with the permission of the Health & Social Care Information Centre, all rights reserved.
Data Sharing Statement
The data that support the findings of this study can be available by applying it to the Independent Scientific Advisory Committee for MHRA database Research, United Kingdom.
Ethics Approval Statement
The study was approved by the Independent Scientific Advisory Committee for MHRA Database Research, United Kingdom (Protocol 18_022R). Only approved researchers can gain access to the data, and research applications are subject to a rigorous research data governance approvals process (https://www.hra.nhs.uk/planning-and-improving-research/application-summaries/research-summaries/clinical-practice-research-datalink-cprd-research-database/).
Acknowledgment
The abstract of this paper was presented at the seventh annual meeting for the Danish society for Gastroenterology and Hepatology, 2019, as a poster presentation with interim findings. The poster’s abstract with the title “Is smoking a risk factor for autoimmune hepatitis? An English registry-based matched case–control study” was published in the corresponding abstract book (https://dsgh.dk/wp-content/uploads/2022/06/abstract2019-1.pdf).
Author Contributions
All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Disclosure
LB and HO are currently employees of Evidera, a business unit of PPD, a ThermoFisher Scientific company. Evidera was not involved in the conduct of the research or preparation of the article. LG, CJC, TRC, PJ, and JW declare that they have nothing to disclose with respect to this manuscript.