The Lewis blood group—a new genetic marker of ischaemic heart disease

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Abstract
In a cohort of 3383 men aged 53 to 74 in the Copenhagen Male Study we investigated the association between ischaemic heart disease (IHD) and the Lewis blood group, assigned to chromosome 19. Among men with the Le(a ‐ b ‐) phenotype, 8% had a history of non‐fatal myocardial infarction, among others the frequency was 4%. The corresponding odds ratio was (95% confidence interval: CI) 1.9 (1.2–3.0) P < 0.01. men with Le(a ‐ b ‐) had a risk‐factor profile and pattern of disease resembling that of Reaven's syndrome X. In a subsequent prospective study 343 men with arteriosclerotic stigmas were excluded. The men had their morbidity and mortality recorded over the next 4 years. One‐hundred‐and‐one men suffered IHD; 26 dying from IHD. In total 162 men died. Men with Le(a ‐ b ‐) had an increased risk of death from IHD compared with others. Adjusted for age, relative risk (RR) (95% CI) was: 4.4 (1.9–10.3), P < 0.001, and for all causes of mortality: RR = 1.6 (1.0–2.6), P < 0.05. Men with the Le(a‐b‐) phenotype had an increased risk of an IHD event compared to men with other phenotypes (RR = 1.6 (0.9‐2.8), P = 0.10) and a significantly higher IHD case fatality rate (RR = 2.8 (1.5‐5.2), P = 0.0]). The finding that the Le(a‐ b‐) phenotype is a genetic marker of IHD risk may have implications in terms of prevention. The Le(a‐b‐) phenotype may also contribute to providing an explanation for the substantial ethnic differences found in the incidence of IHD. The similar risk‐factor profile and pattern of disease found between Le(a ‐ b ‐) men and individuals with Reaven's syndrome X is hypothesized to be due to a close genetic relationship on chromosome 19.