Objectives: To test the hypothesis that long-term occupational exposure to airborne pollutants is a stronger risk factor for ischaemic heart disease (IHD) in men with blood type O than in men with other ABO phenotypes.
Design: Cross-sectional and prospective study taking into account potential confounders.
Setting: The Copenhagen Male Study.
Subjects: 3321 men aged 53-74 years.
Main outcome measure: Lifetime prevalence of myocardial infarction and incidence of IHD in an 8-year follow-up among men without overt cardiovascular disease.
Results: Among men with phenotypes other than O no association was found between airborne pollutant exposure and IHD risk. Among men with blood type O (P = 1417, 42%), 4.7% had a history of myocardial infarction, as compared with 5.7% among men with other phenotypes (P = 1904, 58%). Long-term occupational exposure (> 5 years of exposure) to various airborne pollutants: soldering fumes, welding fumes and plastic fumes was associated with a significantly increased lifetime prevalence of myocardial infarction. Odds ratios (95% confidence limits) for these factors were 3.0 (1.6-5.8), P = 0.002, 2.1 (1.05-4.2), P = 0.05, and 8.3 (2.6-27.0), P = 0.003. In an 8-year follow-up a similar though weaker association was found with a significantly increased risk for those exposed long term to soldering fumes: 1.8 (1.0-3.2), P = 0.05.
Conclusion: The finding of a quite strong interplay between airborne pollutants, ABO phenotypes, and risk of IHD, may open up new possibilities for clarifying the roles of the ABO blood group and air pollution as cardiovascular risk factors.