Parental history looms as key risk factor for MI

Having a patient with a history of myocardial infarction nearly doubled a person’s own risk of future MI, even after accounting for other risk factors, according to an analysis of a large case-control study.

The findings are consistent in all regions of the world.

INTERHEART, a multinational case-control study, involved 15,152 patients who presented with a first MI and 14,820 age- and sex-match control subjects between February 1999 and March 2003. Previous analysis had identified nine variables for determining MI risk: abnormal lipids, smoking, hypertension, diabetes, abdominal obesity, psychosocial factors, physical activity, fruit and vegetable consumption, and alcohol consumption.

The current analysis included 12,149 patients presenting with a first MI and 14,467 control subjects. They obtained data on demographic factors, socioeconomic status, and risk factors for all participants, and performed genetic analysis in 8,795 participants using a panel of 1,536 single nucleotide polymorphisms (SNPs) from 103 genes believed to be associated with MI or risk factors for MI.

In 18.1% of cases and 12% of controls, either parent had a history of MI, while both parents had a history of MI was present in 7.5% of cases and 4.9% of controls, while 121.7% of cases and 8.1% of controls had a paternal history of MI in either parent.

The relationship between parental history and MI risk remained after adjusting for the nine INTERHEART risk factors. Genetics risk scores also didn’t alter the relationship. The researchers calculated genotype scores for 3,372 cases and 4,043 controls, and found that the genetic risk scores were not greater in those with a parental history of MI than in those without.

Parental history approximately doubled an individual’s risk of MI, and the risk increased if both parents had a history of MI, especially if it occurred at a younger age.

Specifically, the odds ratio of an individual having MI was 1.81 if either parent had history of MI (1.74 after adjusting for other risk factors). When either parent had an MI at age 50 years or older, the odds ratio fell to 1.67 — but it rose to 2.90 if both parents had an MI at age 50 or older.

The odds ratio was 2.36 for those patients with one parent who had an MI before age 50, but increased to 3.26 if both parents had an MI and one parent were younger than age 50. If both parents had an MI before age 50, the odds ratio reached 6.56.

The study results suggest that parental history of MI is an independent predictor of an individual’s risk of future MI — even after adjusting for age, sex, region, and other risk factors. The association between parental history of MI and MI is consistent across geographic regions, age, sex, and socioeconomic subgroups.