Family history as a risk factor for heart disease

Screening the brothers or sisters of those who have heart attacks at a young age could be a way of reducing the number of heart attacks in young people, The Times reported. It explained that siblings have “double the risk of developing [coronary heart disease]”. In addition, husbands, wives and partners are also at risk; as The Guardian explained, “those who share a home probably also share a lifestyle”. A research team has shown that screening could cut the rate of premature heart attacks by 40%.

This article was based on a study that looked at the findings of a variety of different studies, and has reported these selectively. Although family history is a risk factor for heart disease, care should be taken in drawing conclusions from these particular findings alone. The idea of screening young people considered to be at risk is a complex one that needs further consideration than is offered by this non-systematic review of the literature.

Where did the story come from?

Clara Chow and colleagues of the University of Glasgow conducted this research. The study was funded by a Wellcome Trust award and a CSO international fellowship and was published in the peer-reviewed British Medical Journal.

What kind of scientific study was this?

The researchers reviewed the medical literature about cardiovascular risk factors and searched electronic databases.

Using the studies they found, they looked at the proportion of siblings of patients with premature heart disease who also had the condition themselves, and looked at how this risk varied across factors such as age at time of first heart event and number of affected relatives. They also tried to look at the influence that additional medical and lifestyle factors may have.

The researchers then made recommendations for using hospital admissions for premature heart attack to identify and screen high-risk relatives.

What were the results of the study?

They researchers give examples of prevalence findings from the studies they found, for example in one study 10% of siblings also had heart disease, in another, 12%, and in another 16% of first-degree relatives of heart attack survivors had themselves suffered a heart attack.

The researchers compared the odds of heart attack in first degree relatives, siblings, or twins that had been calculated in a number of studies, and found that the risk ranged from a two-fold increase in several studies to up to 15-fold in one twin study. They also reported the high prevalence of some modifiable risk factors for heart disease that certain studies had found to be present in siblings; these include smoking, high blood pressure and obesity.

The researchers then discuss the findings of a survey assessing whether guidance is being followed to screen first-degree relatives of those with premature heart disease and whether they have been receiving treatment. They consider suggested ways to screen at-risk people (e.g. identifying on hospital admission of siblings), and to treat them, such as using the “polypill” (which combines small doses of several cardiovascular medications). The findings of one study estimated a reduction in risk of heart attack of 42% if middle-aged people with a family history of heart disease were treated. 

What interpretations did the researchers draw from these results?

They conclude that people with a high overall risk of coronary heart disease should be treated. They acknowledge the difficulty of identifying such people, but suggest that identifying siblings of individuals who are admitted with “premature” heart attack may be one approach. They say that “first-degree relatives are an obvious but neglected group at which primary prevention should be targeted.”

What does the NHS Knowledge Service make of this study?

Family history is a widely acknowledged and accepted significant risk factor for heart disease and it is important that this should be recognised in all individuals who have affected first-degree relatives. However, this study has several flaws and care must be taken when interpreting the risk figures from it and reporting them in the way that the news articles have done.

• As this was a narrative review, it is not certain whether the entire body of evidence has been presented. It is not clear how the authors decided which studies to discuss and which not to discuss.
• It is difficult to draw firm conclusions about how to address a particular patient group from the evidence presented in this review. The studies included have different methodologies, different patient populations, have looked at different relatives and use different methods to analyse their data.
• There is little information in this report about the individual study details which allows a consideration of their reliability; and the calculated risks have no indication of the strength and significance of the findings. 
• Although the study reports all of these cases of heart attack as being “premature” there is no indication of the ages of the patient being considered.

Care needs to be taken when reporting stories such as this is the news. Family history is a risk factor, but there are many others such as smoking, high blood pressure, raised cholesterol, diabetes, and other medical conditions. All of them need appropriate identification and monitoring.

Sir Muir Gray adds...

Everyone in the UK is at high risk of heart and other vascular diseases. People who have had a heart attack or other type of vascular problem diagnosed, for example, a minor stroke, are at very high risk.

Close relatives of people who have a heart attack under the age of 50 have condition known as familial hypercholesterolaemia and these people are at very, very high risk of heart disease. The simplest way to find these people is by asking the close relatives of people who have a heart attack under the age of 45-50 if they would like their risk of heart disease to be assessed. This could be done routinely if services were better organised.