Smoking and Alcohol Increase Risk of IBD: A Mendelian Randomization Study
Cigarette smoking and coffee and alcohol consumption have been extensively studied for their association with inflammatory bowel disease (IBD) pathogenesis. In a study published in the journal INFLAMMATORY BOWEL DISEASES on July 06, 2020, researchers have reported a positive positive association between the age of smoking and ulcerative colitis (UC) and between alcohol consumption and Crohn's disease (CD).
Crohn's disease (CD) and ulcerative colitis (UC) are widely associated with smoking in epidemiological studies, whereas there are conflicting results for the association between CD and UC for both coffee and alcohol consumption. Therefore, researchers of the University of Ioannina, Greece, conducted a study to investigate whether cigarette smoking and alcohol and coffee consumption are causally associated with either CD or UC.
Researchers used a Mendelian randomization (MR) analysis to evaluate the effect of the exposure factors on CD and UC risk. They included a total of 540 single-nucleotide polymorphisms (SNPs) as instrumental variables for the MR analysis: 10 SNPs for an age of smoking, 47 for CPD, 363 for smoking initiation, 22 for smoking cessation, 90 for drinks per week, and 8 for coffee consumption. They also used sensitivity analysis, to test for any directional pleiotropy.
Key findings of the study were:
• Upon analysis, researchers have found evidence for a positive causal association between the age of smoking initiation and UC risk and between alcohol consumption and CD risk, which disappeared after sensitivity analysis for both associations (P > 0.05).
• However, they found no evidence for a causal association between cigarettes per day, smoking initiation, smoking cessation and coffee consumption variables and UC or CD.
The authors concluded, "We found no clear evidence that either genetically predicted smoking, coffee consumption, or alcohol consumption are causally associated with the risk for CD or UC, although our findings indicate a potential positive association between the age of smoking and UC and between alcohol consumption and CD."
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