GRAPEVINE, TEX. — A strong family history of heart disease can increase an individual's future risk for coronary heart disease fourfold, and even a moderate family history can lead to a twofold increase in risk, a population-based study has shown.
“Most clinicians limit family history assessment to the presence of early-onset disease in a first-degree relative,” Maren Scheuner, M.D., said at a meeting sponsored by the American College of Medical Genetics. “However, familial risk is influenced by the number of affected relatives, their degree of relationship and lineage, and age at diagnosis.”
By analyzing data on 4,035 respondents to a national mail survey called HealthStyles, the researchers found that even a moderate history of coronary heart disease (CHD) increased the risk of CHD. Additionally, a strong family history of stroke also increased the CHD risk.
“If you have a family history of CHD, we know that it increases the risk,” said Dr. Scheuner of the department of health services at the University of California School of Public Health, Los Angeles. “We have shown that a family history of stroke also influences the risk of CHD.”
The researchers stratified respondents' family history of CHD and stroke as weak, moderate, or strong. Those with a strong family history had one or more family members with onset of heart disease or stroke at or before age 60. Those with a moderate family history had one or two family members with heart disease or stroke at a later age. Those with a weak family history had no relatives with heart disease or stroke or only one or two affected second-degree relatives. The survey also obtained self-reported information on risk factors such as diabetes, hypertension, high cholesterol, and obesity.
Individuals with strong family histories of CHD were four times as likely to have the disease, compared with those with a weak history. If three or four risk factors are present—such as diabetes, high blood pressure, high cholesterol, and obesity—the risk is increased 27 times given a strong familial CHD risk, compared with those with a weak family history of heart disease and no risk factors. If only two risk factors are present, then the risk is increased 19 times, and if no risk factors are present, then the risk for CHD associated with strong familial CHD is increased only twofold.
Turning to the risk of stroke, a person with a strong family history of CHD has 2.5 times the risk of stroke as a person with a weak family history of CHD. And an individual with a strong family history of stroke has a threefold increase in the risk of a stroke and a twofold increase in the risk of CHD, she reported.
A strong family history of CHD was also associated with a 1.5-fold increased risk of diabetes, high cholesterol, high blood pressure, and obesity. A strong family history of stroke was associated with a twofold increase in diabetes and a 1.5-fold increase in high blood pressure and obesity, respectively.
Moderate family histories of CHD resulted in a twofold increase in CHD, but not an increased risk for stroke, diabetes, high cholesterol, high blood pressure, or obesity. If there was a moderate family history of stroke, the risk of stroke was increased, but the risk for the other conditions was not increased.
Survey respondents were 60% female and 72% white, with a mean age of 48 years. Overall, 6.4% had a personal history of CHD, 4.2% had a personal history of stroke, and 12.3% had a personal history of diabetes. More than 15% of the respondents reported a family history of all three conditions. Almost one-third of respondents reported a strong family history of CHD; about 15% reported a strong family history of stroke.
The findings show that familial risk algorithms for CHD and stroke that incorporate characteristics such as age at diagnosis, number of affected relatives, and their degree of relationship and lineage, can stratify cardiovascular risk as moderate (about a 1.5- to 2.5-fold increase) or strong (about a 2.5- to 5-fold increase) Dr. Scheuner said.
Modifiable cardiovascular risk factors such as diabetes, high cholesterol, hypertension, and obesity are associated with strong familial CHD and stroke risk, and when present they substantially increase the cardiovascular risk.
The absence of risk factors diminishes the association between familial risk and CHD or stroke, she said.