A: Although most of us think only in terms of family history, and some diseases do tend to "run" in families, that doesn't necessarily mean that risk for developing the same medical conditions as other family members is automatically greater, or that we are at little or no risk for developing diseases or illnesses that haven't appeared in our families. When assessing risk for developing cancer, heart disease, diabetes, arthritis and other diseases or illnesses, more than family medical history comes into play.
Susceptibility to disease is determined by three factors: personal health habits, family health history, and the incidence of disease in the community. Each area impacts the other, and all can change over time, thereby changing our risk for developing certain diseases or illnesses.
Family health, community health, and our own health affect each other in many ways. In general, having several family members who've had the same disease predisposes us to developing the same disease. Living in a community with a high incidence of certain diseases predisposes us and our families to developing the same conditions. Our own health habits minimize or increase our risk for developing illnesses or diseases that may or may not be prevalent in our families or communities.
The health histories of our families and communities, and our own health habits, change over time. When we are young, our parents may be healthy. Years later one parent may develop heart disease, thereby increasing the probability that we may also develop heart disease. As we age, we may be the first in the family to develop a cancer that has been known to run in families. Family members would then need to assess their own risk of developing the same cancer. Eating and drinking habits change as we age, affecting risk for dietary-linked diseases. Quitting smoking, beginning an exercise program, moving to a community with more or less pollution -- or even greater or lesser amounts of sunshine -- all can change our risk for developing certain medical conditions.
Paul Gordon, M.D., and Craig McClure, M.D., acting co-heads, Department of Family and Community Medicine at The University of Arizona College of Medicine
Q: How likely am I to get a disease a distant family member has just because we're related?
A: In determining susceptibility to disease, the "degree of closeness" of a relative and the age at which a family member develops a disease are important. Cancer or heart disease that develops in a 80-year-old family member are more likely caused by the accumulated effects of lifestyle or environmental factors. Cancer or heart disease that develops in a 20- or 30-year-old relative are more likely due to a genetic predisposition, which increases your chances of developing those diseases.
We are most likely to develop the same diseases that our immediate family members-- mothers, fathers, sisters and brothers--develop. The health histories of our aunts, uncles and cousins are less likely to impact our own health. Family members who are not blood relatives-- spouses and in-laws--also can affect our health. We are more susceptible to the illnesses of those who live with us. Even caring for an ill family member can cause us to develop such stress-related diseases as arthritis.
Often, diseases that run in families are caused by inherited genes, units of material in our cells that contain information for all aspects of our growth and development. We inherit all of our genes from our parents. Research has shown that a predisposition to certain diseases is linked to inherited genes. About five percent of women with breast cancer, about 10 to 15 percent of patients with colon cancer, and a percentage of lung cancer patients have inherited a gene that has made them susceptible to developing these cancers. Heart disease that develops in younger people is usually the result of an inherited gene. Type II diabetes, which occurs mainly in people over age 40, is considered to be a genetically inherited condition, while juvenile diabetes is not.
Because family physicians are trained to treat patients within the context of the family and the community, they are especially qualified to help determine the risk for developing certain diseases, and to help develop a personal prevention plan to minimize health risks.
Paul Gordon, M.D., and Craig McClure, M.D., acting co-heads, Department of Family and Community Medicine at The University of Arizona College of Medicine