Filling out a medical form can be sobering. It may ask family medical history “did your parent, grandparent, sibling, or other close relative ever have (or die from) the following . . . ?” And then come the little boxes: heart attack, cancer, diabetes, stroke, mental illness, etc. You probably have to check two or three of these boxes. These are the big disorders that touch all families. It would be unusual, actually, for a person to be able to say that nobody in the family ever had heart disease or some form of cancer. But what do these check marks mean? Are you fated to follow the same path?

Interpreting a family medical history is no easy matter. If your father died of a heart attack, that’s important information, up to a point. But at what age? What about his father? If your mother had lung cancer, was she a smoker? More important, are you? A family tree that’s thick with premature deaths is a legitimate worry—two or three close relatives, for example, who died in their forties from colon or breast cancer. Onset of disease at an early age can be a sign of genetic disorders. But one aunt who died of colon cancer at age 75? It’s hard to say if that means increased risk for you, though on the other hand, you should not ignore it. It could be one more reason not to put off colon cancer screening.

And though our parents pass on genes and genetic tendencies to diseases, they may also “pass on” other tendencies—healthy or unhealthy eating patterns, positive or negative attitudes toward exercise and physical activity, and so on. What we do, or don’t do, interacts with what we have inherited. The era we live in, and our social stratum, affect our health. Your parents may have grown up in a society where smoking was the norm, while you live in one that frowns on the habit.

Except in rare instances, your genes are not your fate, or at least are only part of it. Here are some suggestions for thinking about your family medical history.

What genes are

Genes are the chemical data, or blueprint, that we inherit from our parents. Normally cells in the body, except sperm and eggs (reproductive cells), contain the same 46 chromosomes arranged in 23 pairs. Each pair includes one chromosome originally contributed by the mother via the egg, and one by the father via the sperm. Each chromosome contains large numbers of genes—so that the total number in a cell is about 38,000. Genes are sequences of DNA (deoxyribonucleic acid)—the “molecules of life.” They direct the manufacture of proteins and thus every aspect of the body’s functioning. They determine our hair color, eye color, and hundreds of other traits. They determine, or help determine, our susceptibility to diseases and disorders. A few diseases are carried by a single gene. But most diseases are multifactorial—influenced by several genes, the passage of time, and the social and physical environment. That is, a gene or genes that may put you at risk for, say, Type 2 diabetes, might not come into play if you maintain a healthy weight, eat sensibly, and exercise as you age.

Nobody enters the world with perfectly healthy genes—each of us possesses a certain number of genes that can cause disease. Fortunately genes come in pairs, so a dominant normal gene can protect you from a recessive abnormal one. Relatively few genetic disorders are caused by a single abnormal dominant gene. Huntington’s disease is one example of this—if a parent has this disorder, there’s a 50-50 chance that a child will. But  most serious genetic disorders, such as cystic fibrosis, sickle cell disease, and Tay-Sachs disease, are caused by a pair of abnormal recessive genes. A child must inherit the abnormal gene from both parents for the disorder to manifest itself. If the child carries just one recessive gene tagged for the disease, it will be overruled by the dominant normal gene it’s paired with. The child will then be a carrier of the trait, but will not develop the disorder.

What good is genetics?

The science of genetics is still young. It is a grand advance in knowledge, dazzling in its scope and promise, already with many practical applications in medicine, law, agriculture, pharmacology, and other areas. But the therapeutic role of genetics remains unclear. Researchers have decoded the entire human genome, and nearly every day the newspapers report the discovery of yet another gene—a gene for Alzheimer’s disease, a gene for obesity, and so on. However, while people may assume that identifying a gene for this or that disorder means that the faulty gene can be repaired, and the disease prevented or cured, thus far it has not turned out that way.

A case in point is the “breast cancer gene” or genes. It’s possible to identify two abnormal genes in many high-risk women—but there is no way to “repair” these genes. The only way to keep these women from developing breast cancer is pre-emptive surgery (removing both breasts), and even this may not work. Furthermore, it has become clear that women carrying the genes do not have as high a risk of getting breast cancer as was once thought. And there’s no way to know when they might get it—at age 30 or 75? In addition, these genes are responsible for only a small number of breast cancer cases. Only about 5 to 10% of women with breast cancer have the breast cancer gene(s).

It’s even more complicated when you look for the genes behind heart disease, diabetes, arthritis, Alzheimer’s disease, osteoporosis, and other chronic diseases. Many different genes may be at work, and they all are subject to environmental influences over time. A high dose of radiation or an infection may harm genes; a diet rich in vitamins, minerals, and phyto­chemicals may help protect them. Indeed, the so-called map of the genome has turned out not to be a map at all, if by a map we mean something two-dimensional, showing clearly defined roads and routes that lead from here to there. The genome seems rather to consist of interlocking parts that communicate among themselves, are influenced by the environment, and change with the passage of time.

How to read the text

Family medical history will continue to be more important to most people’s health strategies than genetic testing. There may never be a way to predict which diseases you will get, let alone when you will get them, but family history can help guide you to make healthy lifestyle choices, as well as motivate you to stick with them.

Doctors, too, are trying to figure out how family medical history can be made more useful as a guide for healthy living. Not everybody pays attention when the experts say “maintain a healthy weight,” “get regular exercise,” “don’t smoke.” Would more careful examination of family history be a motivator for most people? Should doctors spend more time discussing it with their patients? If, for example, your father died pre­maturely of a heart attack, this is good reason for periodic blood cholesterol testing, among other measures. If you’re a woman and your mother has or had osteoporosis, you’ll want to begin bone density testing after menopause (or earlier if your mother was diagnosed early) and to take steps to prevent or delay bone loss.

It is worthwhile to make a permanent record of your family’s medical history, for yourself and others, especially if you have children. List full names, birth and death dates, known illnesses (including mental illness), cause of death, age at death, and other details if you know them, from your grand­parents on down. Were they smokers? Heavy drinkers? Were they physically active? What did they do for a living? These things, of course, have a strong impact on health. It may take some digging to find all this out.

Whatever you discover about your family medical history, treat it as one of many tools you can use to safeguard your health.