Environmental Effects on IMIDs

On the third day of the 2023 Interdisciplinary Autoimmune Summit, Gilaad Kaplan, MD, MPH, FCAHS, presented his session, “The Effects of the Environment on Immune-mediated Diseases (IMIDs): Inflammatory Bowel Disease (IBD) as a Case Study,” with the objective to study the evolution of IBD across geography and time.

Dr Kaplan started with 4 epidemiologic stages in the evolution of IMIDs: emergence (stage 1), acceleration in incidence (stage 2), compounding prevalence (stage 3), and prevalence equilibrium (stage 4). He asked the fundamental question, “Will the incidence of IBD in newly industrialized countries mirror the progression of IBD in the Western world during the 20th century?”

After reviewing studies of IBD incidence and prevalence in Malasya, Dr Kaplan reviewed a study of prevalence per 100 000 of IBD, ulcerative colitis, and Crohn disease (CD), wherein Malaysia recently transitioned from stage 1 (emergence) to stage 2 (acceleration in incidence) and Canada has been in stage 3 (compounding prevalence) for roughly 3 decades.

Next, Dr Kaplan provided a concise overview of environmental exposures across the continuum of age. “Environmental exposures occurring across the continuum of age, such as exposures at different ages from infancy to adolescence to adulthood, result in different risks in developing IBD,” he stated.

Dr Kaplan also discussed why it is difficult to study the environmental risk factors of IBD. “Many environmental factors have been studied but none explains the pathogenesis of IBD,”he said. He used smoking as an example. “Smoking increases the risk of CD and worsens the prognosis in the Western world but not in Asia,” he indicated. Regarding gene-environment interactions, Dr Kaplan noted, “Patients with CD are less likely to carry a NOD2 mutation and more likely to have a history of smoking as their age at diagnosis rises.”

Lastly, Dr Kaplan concluded with prevention advice for clinicians to share with their patients:

• Do not start smoking
• Practice judicious use of antibiotics
• Avoid vitamin D deficiency
• Engage in physical activity and get regular sleep
• Maintain a healthy weight and low stress levels
• Consume fruits, vegetables, fiber, and fish/oil, and avoid ultraprocessed foods and refined sugars

Reference
Kaplan G. The effects of the environment on immune-mediated diseases: IBD as a case study. Presented at: Interdisciplinary Autoimmune Summit; April 26–28, 2023; Virtual.