Nicotine and Inflammatory Disease in Humans: A Systematic Review

Summary Introduction Previous studies have shown that nicotine interacts in inflammatory pathways and may have both pro- and anti-inflammatory actions. The aim of this study was to carry out a systematic review of publications investigating the inflammatory effects of nicotine in models of human disease. Methods The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) checklists were followed during the design and implementation of this study. Searches were carried out across PubMed, Science Direct, and the Cochrane Library. Articles were included if they were published in English, in peer-reviewed journals, reported an effect of nicotine in the treatment of a clinical condition, experimental studies or clinical trials which investigated an effect of nicotine administration in patients with a clinical condition or epidemiological studies which investigated an effect of nicotine administration in patients with a clinical condition. Results Thirty-eight studies were identified and categorized into disease areas before systematic review. Nineteen studies were related to digestive diseases (primarily Crohn’s disease and ulcerative colitis), six to atherosclerosis, five to skin and healing, four to pain and infection, three to pulmonary sarcoidosis, and three to multiple sclerosis (one study reported data on three disease areas). Risk of bias assessment was not carried out, but the general quality of the studies was low, mostly offering preliminary data in small numbers of participants. No consistent effects of nicotine treatment (primarily through use of transdermal nicotine patches or nicotine chewing gums) were reported across any of the disease models. Conclusion No reliable evidence of a pro- or anti-inflammatory effect of nicotine was observed in patients with any of the diseases included in this study.