Lewis phenotypes, leisure time physical activity, and risk of ischaemic heart disease: an 11 year follow up in the Copenhagen male study

Abstract

Objective: To test the hypothesis that the predictive value for risk of fatal ischaemic heart disease associated with Lewis phenotypes depends on the level of leisure time physical activity.

Design: Prospective study controlling for alcohol, tobacco, serum cotinine, blood pressure, body mass index, serum lipids, work related physical activity, and social class.

Setting: The Copenhagen male study, Denmark.

Subjects: 2826 white men aged 53-75 years without overt cardiovascular disease; 266 (9.4%) had the Le(a-b-) phenotype.

Main outcome measure: Incidence of death from ischaemic heart disease during 11 years.

Results: 107 men died of ischaemic heart disease. Among men with a low level of leisure time physical activity (</= 4 hours/week moderate or </= 2 hours/week more vigorous activity), being Le(a-b-) was associated with an increased risk of having a fatal ischaemic heart disease event compared with men with other Lewis phenotypes (relative risk (RR) 2.7, 95% confidence interval (CI) 1.4 to 5.2; p < 0.01). Among men with a high level of leisure time physical activity, the RR associated with being Le(a-b-) was 1. 3 (95% CI 0.5 to 3.1; NS). Compared with all other alternatives tested, being Le(a-b-) and having a low level of leisure time physical activity was associated with an RR of 3.2 (95% CI 1.7 to 5. 8; p < 0.001). As a point estimate and adjusted for confounding variables, among men with low leisure time physical activity the attributable risk associated with Le(a-b-) was 12%-that is, assuming that all sedentary men had phenotypes other than Le(a-b-), 12% of all fatal ischaemic heart disease events would not have occurred. The corresponding point estimate among those more active was 2%.

Conclusions: The excess risk of fatal ischaemic heart disease in middle aged and elderly men with the Le(a-b-) phenotype is strongly modified by leisure time physical activity. Public health and clinical implications may be important in populations with a predominantly sedentary lifestyle and in a high proportion of men with the Le(a-b-) phenotype.