Does heart disease, asthma, or maybe a certain type of cancer run in your family? Patients often ask me if a particular medical condition is genetic, usually because they have made such an observation in their own family. My answer is always the same: Everything is genetic.
Of course, it isn't quite that simple. The full answer is that every aspect of health and disease is due to a combination of genetic, environmental and behavioral factors. The non-genetic exposures include everything from the air we breathe and the things we eat and drink to our physical activity and our methods of transportation.
You can pick any "classic" genetic disease (sickle cell anemia, cystic fibrosis, Marfan syndrome...) and find differences from one patient to the next, in part because they have had different exposures and life experiences. The opposite is also true: Our response to an infection or ability to survive major trauma is partially affected by our genetic make-up.
But most of the common health problems are due to an undetermined mix of genetic and environmental factors. These conditions include high blood pressure, heart attack, stroke, arthritis, gout, cancer, diabetes, asthma, low bone density, depression, glaucoma, and just about any other medical illness you can think of. We now know several of the lifestyle and environmental risk factors for many of these diseases. And we're starting to identify more and more of the genetic factors, too.
A complete understanding of all the different causes of even the most common diseases remains a distant goal. In the meantime, however, one of the best predictors we have of a person's future risk of disease is the family medical history.
Not only does the family history tell us about the genetic traits passing down through the generations, it also automatically includes whatever environmental and cultural habits are shared by relatives in the same family. Happily, family history is also one of the least expensive, safest, and easiest medical screening tests available!
Research indicates that most of you already know at least some of this. The 2004 HealthStyles Survey showed that 96 percent of United States residents feel that knowledge of family health history is important to personal health.
However, less than 30 percent of those surveyed had ever tried to collect and record their family medical history. In an effort to boost that number, the United States Surgeon General has declared Thanksgiving "Family History Day".
Of course, you can collect family health information any time of the year. But family gatherings during the holiday season are a great chance to get started.
The people who are most important to include are your nearest relatives, because they are the ones with whom you share the most behaviors, environmental exposures, and genes. At the genetic level, you are 50 percent identical to each of your 1st-degree relatives—parents, brothers, sisters, and children. Next closest are your 2nd-degree relatives—grandparents, aunts, uncles, nieces and nephews—to whom you are 25 percent identical.
Cousins, great aunts, great uncles, and other distant relatives share only 12.5 percent or fewer of the same genes. It's fine to include them, too, but the 1st- and 2nd-degree relatives will provide the most important information.
Here's a list of the kinds of information you should try to learn about each of your relatives:
Degree of relationship. Since we're tracking genes here, make note of exact relationships. Half-brothers and half-sisters (sharing the same mother or father, but not both), for example, are more distantly related than full siblings, and step-siblings don't actually share any identical genes (because they "married into" the family). Also mark down any twins, and try to determine if they are identical twins (which means their genes are completely the same) or "fraternal" twins (which are the same as regular siblings genetically).
Current age, or age at death. It can be very encouraging to know if your family has a history of living to an old age. It's also helpful to know if a relative is or was too young to develop certain medical problems—such individuals can't be counted as having escaped those particular illnesses. If you don't know someone's exact age, try to guess within a decade (e.g., 50s or 70s).
Cause of death. Try to be as precise as you can in determining this. "Heart disease" could mean heart attack, congestive heart failure, irregular heartbeat, or several other things.
Likewise, we've known for decades that "cancer" isn't one specific illness. Even a specific organ (lung, kidney, brain, etc.) can be vulnerable to several different types of cancer. Cancer often spreads (metastasizes) to multiple different parts of the body, but the crucial information to find out is the specific type of cancer and the particular site where it first began.
Many people know that a relative had "female" cancer, but it is valuable to know if that means cancer of the breast, ovary, uterus, or another "female" organ. Another tricky one is "stomach" cancer. In medical language, the stomach is where the food goes after you swallow and it passes down your throat. The non-medical use of the word "stomach" often includes the colon, liver, pancreas, and many other organs in the belly (often including the "female" organs). Again, knowing exactly where the cancer started can make a huge difference in evaluating the risk to other family members.
All medical problems. Remember—everything is genetic, so include all of the obvious things, and anything else you think might be important. Anyone with drug or alcohol addiction? Mental retardation or learning difficulties? Emotional problems? Trouble getting pregnant or recurrent miscarriages? Birth defects? Obesity? Some people have a particular birthmark or behavioral characteristic that seems to run in the family—you never know what might turn out to be important.
Wherever possible, try to write down a specific diagnosis or characteristic, rather than just listing symptoms. For example, rheumatoid arthritis and osteoarthritis are completely different from each other, and knowing that level of detail is much more informative than saying that Aunt Sally had "joint pain" or "arthritis." Surgeries are okay to include, but it is more helpful to know why the surgery was needed (that is, the diagnosis) than what kind of operation was done.
Age of onset. When a person develops a disease at a much younger age than normal, that can be a warning sign of stronger genetic risk running in the family. Try to learn at least the approximate age at which each medical problem began.
Major environmental risks (or their absence). Smoking is the most obvious thing to consider here. If you're a non-smoker, you might not need to worry so much about developing the same lung cancers that happened to your relatives who smoked. On the other hand, if you have a family history of lung cancer and yet nobody was exposed to tobacco, asbestos, or radon, that could be very significant for you. Diet, work history, and hobbies are some other examples that might involve toxic exposures or risk of injury.
You can get a lot of helpful information about gathering and recording your family history from the National Society of Genetic Counselors. You can also use this online family history tool to enter your data and then have a family tree drawn for you. This tool will ask specifically about 6 medical conditions, but you can enter all of the other information you learn, too.
In a future entry, I'll discuss how to use all of this valuable information. For now, though, I urge you to get started collecting your own family history. And remember: This Thanksgiving, don't just eat turkey with your family, talk turkey about your family!
