Objectives: the aim of our study was to evaluate the independent role of the haptoglobin (Hp) polymorphism as a risk factor for coronary heart disease (CHD) mortality.
Methods: within the framework of the longitudinal part of the Belgian Interuniversity Research on Nutrition and Health (BIRNH) survey, a nested case-control study design was performed through matching the 107 deaths from CHD, occurring within a 10-year follow-up period, with three controls for age and gender.
Results: the distribution of the Hp types was found to be in Hardy-Weinberg equilibrium. Conditional logistic regression analysis for matched sets revealed that the Hp polymorphism was significantly associated with CHD death. Rather surprisingly, the finding was that Hp 1-1 individuals were at doubled risk for CHD mortality compared with the others, the odds ratio being 2.09 (95% CI: 1.22-3.60). The association was independent from other classical cardiovascular risk factors and the Hp concentration, and of comparable magnitude between men and women. Moreover, evaluating the interaction term in a multiplicative model showed that the Hp type did not play a synergistic role in the prognostic value of established cardiovascular risk factors.
Conclusion: in contrast to the findings from cross-sectionally based studies, the results from this longitudinal study show that Hp 1-1 individuals are at elevated risk for CHD mortality.