Aggregation of Deaths from Ischaemic Heart Disease among First and Second Degree Relatives of 108 Males and 42 Females with Myocardial Infarction

Abstract

ABSTRACT. The occurrence of deaths due to ischaemic heart disease (IHD) among first and second degree relatives of coronary patients and among relatives of an equal number of matched controls was studied on the basis of death certificates. The propositi were 108 males and 42 females, who had developed myocardial infarction (MI), males before 65 years of age and females before 70. When compared with controls, a 1 1/2‐fold higher death rate was found among first degree relatives of the propositi and a lower average age at death. The difference in death rate between second degree relatives was not significant, except for maternal brothers. When compared with the death rate due to IHD in the general population, the increase in risk to first degree relatives of propositi was nearly 3‐fold over the expected value, and 1 1/2‐fold to second degree relatives. The age of the propositi at onset of MI did not affect the risk to relatives, whereas sex‐related influence was significant. To first degree relatives of male propositi the risk increase was up to 5‐fold over the expected value. The risk increase was found to be greatest to first degree male relatives of female propositi, or over 7‐fold to fathers and brothers. Mothers and sisters of both male and female propositi showed a 4–5‐fold risk increase over the expected value. The risk increase to second degree relatives was 2 1/2‐fold over the expected value to maternal brothers of male propositi and 4‐fold to such brothers of female propositi. The relatives of controls showed a coronary mortality close to that of the general population. Familial clustering of coronary deaths was found in 8.7% of the families of the propositi and in 4.7% of the families of the controls. The findings of the present study indicate a substantial genetic component in the overall aetiology of IHD, which is more prominent in families of female propositi but hardly of a magnitude to warrant genetic counseling.