Occupational Exposure to Petroleum-Derived Lubricants and Risk of Multiple Sclerosis.

Abstract (English)

BACKGROUND AND OBJECTIVES: Lung irritants such as smoking and organic solvents are established risk factors of multiple sclerosis (MS), with effects influenced by genetic susceptibility, particularly leukocyte antigen (HLA) <i>DRB1*15:01 and HLA-A*02:01</i>. Petroleum-derived lubricants represent another widespread occupational exposure with potential inflammatory properties, yet their contribution to MS etiology remains unclear. This study investigated associations between occupational exposure to petroleum-based lubricants and MS risk, including interactions with smoking and HLA genotypes. METHODS: This investigation was based on a Swedish population-based case-control design. Incident MS cases were consecutively recruited by neurologists at 40 clinics (2005-2015). Inclusion criteria comprised residence in Sweden, age 16-70 years, and a diagnosis of MS confirmed by a neurologist according to the McDonald criteria. Controls were randomly selected from the national population register using density sampling and frequency-matched to cases by age, sex, and residential area. Exposure to petroleum-derived lubricants was assessed using questionnaire data. Logistic regression was used to estimate odds ratios (ORs) and 95% CIs for MS in relation to occupational exposure to petroleum-derived lubricants. Interactions with smoking, <i>HLA-DRB1*15:01</i>, and absence of <i>HLA-A*02:01</i> were assessed on the additive scale using the attributable proportion due to interaction (AP). RESULTS: The study population comprised 2,872 incident MS cases and 6,122 controls (mean age: 34.6 years; 72% female). Occupational exposure to petroleum-derived lubricants was associated with increased MS risk (OR 1.38, 95% CI 1.16-1.65), with a modest exposure-duration response. The association persisted when applying a 7-year exposure lag (OR 1.55, 95% CI 1.27-1.90). A positive interaction was identified between petroleum exposure and smoking (AP 0.34, 95% CI 0.10-0.55). Among the subset with available HLA data (2,070 cases and 2,899 controls), petroleum exposure interacted with the absence of <i>HLA-A*02:01</i> (AP 0.32, 95% CI 0.05-0.59). A similar interaction was observed with <i>HLA-DRB1*15:01</i> (AP 0.19, 95% CI -0.08-0.46), although this estimate did not reach statistical significance. DISCUSSION: Occupational exposure to petroleum-derived lubricants was associated with MS risk, with stronger associations among smokers and participants with established genetic susceptibility. These findings add to the evidence that lung irritants and gene-environment interactions contribute to MS susceptibility but require replication in independent populations.