Dr. Michael Roizen, MD , Internal Medicine, answered
Although many studies have looked at the family history of disease in relation to the onset of disease, only three major studies have correlated overall longevity trends between parents and their children. The Framingham Study, the "Termite" Study, and the Alameda County Study looked at the age of parental death to determine if it predicted longevity of the offspring. Did the two correlate? Yes, but minimally. Each study showed a minor effect. The Framingham Study, the most comprehensive of the three, found about a 6 percent correlation between life span of the parents and life span of their offspring, meaning that many other factors affect longevity as well. If both your parents lived past the age of seventy-five, the odds that you will live past seventy-five increase to some extent. But to what extent? (Note that we are discussing, for the most part, death related to disease. If a parent dies at age forty in a car accident, for example, that provides little information about how long the child will live, although alcohol-induced accidents are a possible exception.)
If you are a man and both of your parents died before the age of seventy-five, then your RealAge (physiologic age) will be as much as 4.2 years older. If you are a woman, your RealAge will be as much as 3.5 years older. If both parents lived past the age of seventy-five, then your RealAge will be 4.2 years younger if you are man, and 3.5 years younger if you are a woman. If no first-degree relative (parent, brother, sister) had breast, colon, or ovarian cancer diagnosed early, you are an additional 0.2 to eleven years younger than if your siblings or parents had those diagnoses. Some genetic conditions, such as being a carrier of the BRCA-1 breast cancer gene, can make your RealAge as much as 17 years older. This is one of the instances where genetics can make a big difference.