Familial aggregation of early-onset myocardial infarction

An inherited predisposition is an important factor in the etiology of myocardial infarction (MI) at a young age. However, the extent of the risk for early-onset MI in relatives of young patients is still unclear, due to the paucity of family history data. Hence familial aggregation of early-onset MI was investigated in a cohort of relatives of Italian patients who had survived MI who occurred at the age of 45 or earlier.

In the framework of a case-control study, lifetime data and early-onset MI status for 11,696 relatives of cases and 8897 relatives of controls were collected using a standardized questionnaire.

Occurrence of early-onset MI in females was very uncommon (Kaplan-Meier risk=0.6%, 95% confidence interval (CI): 0.38-0.82%, for female case relatives), and significantly lower than that for male case relatives (5.0%, 95% CI: 4.41-5.56%). The hazard ratio (HR) for case relatives was approximately 3-fold greater than that for control aunts (taken as reference category). Risk for early-onset MI to siblings (HR=1.7, 95% CI: 1.33-2.18) was significantly different from that to parents (HR=0.9, 95% CI: 0.71-1.16). The familial risk ratio λ(R) was 2.6 (95% CI: 2.30-2.89) for case relatives, using control parents as reference population for early-onset MI risk estimates (i.e. 37 per 100,000 in fathers and 7 per 100,000 in mothers).

We evaluated the risk of early-onset MI by category of relatives, obtaining evidence for familial aggregation of the disease in this Italian sample and providing figures for genetic counselling and planning genetic epidemiological studies.