These APOE genes vary in frequency among the world's populations. The 4 percent of people who have two copies of the E2 gene are especially sensitive to diets rich in fat and cholesterol, on which they are ready candidates for heart disease, as are those with two copies of E4. Frequency differences also have implications for the interplay of human genetics and behavior in shaping individual risk profiles during various sports. Among professional boxers, one in six gets Parkinson's or Alzheimer's disease. The microscopic symptoms of these disorders are similar, though predispositions to them appear to have different genetic bases.
Environment can play a significant role here as well.
Professional boxers would be well advised to be tested and not to box if they have two copies of the E4 gene, which greatly increase the chance of early Alzheimer's disease in people who sustain head injuries. In the years immediately ahead, data on the content of our genomes will become readily available, and probably will become as informative parts of our medical records as family history and blood chemistry are now. Robert B. Eckhardt is professor of developmental genetics and evolutionary morphology in the Department of Kinesiology in Penn State's College of Health and Human Development. This site was developed by Annemarie Mountz .