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The medical community has known and studied heart disease in homogeneous populations for years, determining that a person has a greater risk of heart disease if one or more of their close relatives (parent-child, brother, sister) also had a history of heart disease or having died suddenly from heart problems.
Thus, in certain populations, family history has already been established as a determinant in a person’s predisposition to heart disease. This begs the questions: What constitutes “family history?” Does it simply reflect inherited genetic factors, or does it also represent environmental factors? Do these familial risk factors reflect something other than the tendency for known genetic and environmental risk factors of heart disease to also run in families including high blood pressure, high cholesterol, obesity, diet, physical activity and smoking?
According to a study published in the February 1, 2011, issue of the Journal of the American College of Cardiology, parental history of heart disease nearly doubles a person’s risk in all regions of the world, even after considering all other known risk factors of heart disease. In other words, many unknown genetic and environmental factors running in families remain to be discovered and play an important part in determining one’s likelihood of developing heart disease.
The INTERHEART Study, a multinational, case-control study, examined whether the relationship between parental history of myocardial infarction (MI) – or heart attack – and MI risk is independent of known cardiovascular risks and a small number of genetic variants mostly related to risk factors.
“This study finds that parental history of myocardial infarction, a very easy-to-measure risk factor, approximately doubles your risk of future heart attack regardless of all other risk factors, including ethnicity, gender, and socioeconomic position,” said Clara Chow, MBBS, Ph.D., Head Cardiac Program, The George Institute; Senior Lecturer, University of Sydney; Assistant Professor, McMaster University, and Cardiologist at Westmead Hospital. Dr. Chow is lead author of this study. “If both parents have a history of heart disease, and especially if it occurred at a young age, then the risk increases.”
Dr. Chow and her team concluded that parental history is an important, consistent and global determinant of heart disease. Both maternal and paternal histories are associated with an increased risk, and the younger the incidence in the parent, the higher the risk. After making adjustments for a set of nine risk factors – both biological and behavioral (i.e., abnormal lipids, smoking, hypertension, diabetes, abdominal obesity, psychosocial factors, physical activity, fruit and vegetable consumption, and alcohol consumption) –it was determined that the overall association of parental history is an important indicator.
“While other studies have shown the relationship between parental history and risk, they have not established its independence from the extensive list of other potential explanatory factors as measured by the INTERHEART Study and not established it in other world regions or ethnic groups,” said Dr. Chow.
Because of this, and its very wide applicability, Dr. Chow believes that this will put to rest a number of criticisms that parental history is not that important if other risk factors are well-measured and of uncertain significance in different population groups.
In his accompanying editorial, Themistocles (Tim) Assimes, M.D., Ph.D., Assistant Professor at Stanford University School of Medicine, emphasizes the importance of Dr. Chow’s findings. “This study confirms that unknown genetic and environmental factors play an important role in determining one’s risk of heart disease in all major regions and ethnicities throughout the world. We have much important and challenging research left to do to identify these unknown risk factors, but they seem to be present to a similar degree everywhere in the world. In the meantime, there is no reason we should not use this information worldwide to better predict who is at a higher risk of a heart attack. We can then spend a little extra time counseling these individuals on the importance of lifestyle changes such as weight loss, exercise, and smoking cessation and/or medicines that reduce blood pressure or cholesterol. These interventions can serve to neutralize the excess risk related to a family history.”
The American College of Cardiology is transforming cardiovascular care and improving heart health through continuous quality improvement, patient-centered care, payment innovation and professionalism. The College is a 39,000-member nonprofit medical society comprised of physicians, surgeons, nurses, physician assistants, pharmacists and practice managers and bestows credentials among cardiovascular specialists who meet its stringent qualifications. The College is a leader in the formulation of health policy, standards and guidelines, and is a staunch supporter of cardiovascular research. The ACC provides professional education and operates national registries for the measurement and improvement of quality care. More information about the association is available online at http://cardiosource.org/ACC.