CALCULATING GENETIC RISK

It is estimated that heart disease, cancer and diabetes account for 7 of every 10 deaths in the United States. Like rare genetic disorders, these "common" diseases run in families and can therefore be considered genetic diseases. Because of this, a family history can provide important information about your family's risk of disease. But, is it possible to predict who will or will not develop disease? If so, how is this done?

Common diseases result from the combined effects of multiple genes and environmental factors. This makes it very difficult to predict whether or not an individual will inherit disease.

One reason for this is that the number of genes contributing to so-called "polygenic" diseases is usually not known. The number of genes carried by parents or children that can increase risk is also not known. And, environmental factors can greatly vary an individual's risk of developing disease.

Because more than one gene is involved in most common diseases, resulting inheritance patterns are varied and complex. If a parent has a disease, it does not necessarily mean a child will develop the same disease. So, risk can be estimated but not calculated.

Information in a family medical history must be used to assign an individual to a low, medium, or high risk group. This is done by comparing an individual's family history to data collected from large families affected by a disease. Persons in each risk group share characteristics that correlate with a certain probability of developing a disease.

Risk is easy to calculate for rare disorders caused by a single gene.

Single Disease Gene

Many Disease Genes

But for complex diseases that are influenced by multiple genes, risk is much more difficult to calculate.

Risk must be estimated based on observation of data collected from large families affected by these diseases.

Sometimes it's not possible to have access to medical information from your biological family. But it's still useful to complete a history using your guardian family. This is because family histories capture more than just genetic risk factors.

They also capture cultural, social, and environmental risk factors shared by a family that can contribute to disease.

One goal of genetic research is to identify genes that contribute to these complex diseases, and understand how these genes are influenced by a person's environment and lifestyle choices.

Scientists are beginning to identify whole lists of genes that contribute to each of the major common adult diseases, such as heart disease, cancer and diabetes.

Human DNA was sequenced using robots and computers to reveal that humans have over 22,000 genes! This sequence was completed in April 2003 as part of the Human Genome Project

Utah Health Family Tree
Website coming soon
University of Utah, Utah Department of Health
An interactive online family health history tool that provides a printable report with a drawing of your family tree and risk assessment for many chronic diseases.

Family Health History Toolkit
Utah Department of Health
Downloadable booklet to help families talk about and collect their family health history and share what they learn with their doctor. Can request a paper copy of the toolkit that includes a large poster of the Utah Health Family Tree on which to record your family health history.

My Family Health Portrait
U.S. Surgeon General, Department of Health and Human Services
Can download a paper or web-based family health history recording tool to your own computer. Spanish and English versions available.

Your Family History – Your Future
National Society of Genetic Counselors
Guidelines on how to collect a family health history.

Does It Run in the Family? A Guide to Family Health History
American Folklife Center, American Society of Human Genetics, Genetic Alliance, Health Resources and Services Administration, Institute for Cultural Partnerships
Downloadable booklet that describes the importance of family health history and guidelines for collecting and recording family health history

Supported by the Utah Department of Health Chronic Disease Genomics Program through Cooperative Agreement Number U58/CCU822802 from the Centers for Disease Control and Prevention. The contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention.