Letters

Family history is important in estimating coronary risk

EDITORThe new Sheffield table and its alternatives make little use of a cardinal risk factor that is easy to assess.¹ A family history of coronary artery disease, especially when premature, is a powerful and independent indicator of a person's risk. Failure to include this element will cause these tables to underestimate the 10 year risk of cardiovascular disease and cannot be corrected for by simply adding six years to the patient's age, as suggested in the Sheffield table. The increase in risk depends on the exact details of the family history and the patient's age and sex.

The GISSI-EFRIM investigators (Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto-Epidemiologia dei Fattori di Rischio dell'Infarto Miocardico) showed that a family history of myocardial infarction is an independent risk factor for myocardial infarction, with the number of relatives and the age at which they were affected influencing the strength of the association.² Compared with subjects without a family history, those with one or two affected first degree relatives had relative risks of myocardial infarction of 2.0 and 3.0 respectively.

The danger seems to be greater for women than for men and is especially high if a sister is affected. In one study of patients aged under 60 with myocardial infarction the cumulative risk to women of ischaemic heart disease before age 65 is considerably higher if a sister rather than a brother is affected (26% v 16%).³

Using more precise definitions of a family history allows for a more accurate assessment of coronary risk. An Australian survey found that, compared with an affected parent, an affected sibling carries a relative risk of 2.5 for coronary artery disease, regardless of age.⁴ Hence any female patients defined by the Sheffield table as having a 10 year risk of coronary heart disease of 15% but who have an affected sister of similar age may actually have a risk of over 30%. Family history of coronary artery disease should feature prominently in all guidelines for primary prevention of cardiovascular disease.

John Younger, medical registrar. 
John Hunter Hospital, Locked Bag 1, Hunter Region Mail Centre, Newcastle, NSW 2310, Australia