Smoking and Epstein-Barr virus infection in multiple sclerosis development

Area of Science:

• Epidemiology
• Immunology
• Neurology

Background:

• Smoking is a known risk factor for multiple sclerosis (MS).
• Epstein-Barr virus (EBV) infection, particularly infectious mononucleosis (IM), is also linked to increased MS risk.
• The interplay between smoking and EBV infection in MS etiology remains unclear.

Purpose of the Study:

• To investigate potential synergistic interactions between smoking and EBV infection markers (EBNA-1 antibody levels and IM history) concerning MS risk.
• To determine if current or past smoking status modifies the association between EBV infection and MS.

Main Methods:

• Utilized two Swedish population-based case-control studies comprising 6,340 MS cases and 6,219 matched controls.
• Employed logistic regression to calculate odds ratios (OR) and 95% confidence intervals (CI) for MS risk.
• Assessed additive interaction using the attributable proportion due to interaction (AP) metric.

Main Results:

• Current smokers exhibited higher EBNA-1 antibody levels compared to never smokers (p < 0.0001).
• Significant additive interaction was observed between current smoking and high EBNA-1 antibody levels (AP = 0.3) and between current smoking and IM history (AP = 0.2) regarding MS risk.
• No significant interaction was found for past smoking with either EBNA-1 levels or IM history.

Conclusions:

• Current smoking amplifies EBNA-1 antibody levels, suggesting a biological link.
• Current smoking acts synergistically with EBV infection markers (high EBNA-1 antibodies and IM history) to increase MS risk.
• These findings indicate a shared pathway involving both smoking and EBV infection in the development of MS.