By Ed Yong
The apoliprotein E gene, or ApoE, comes in three forms—E2, E3, and E4. The last one is the problem. People who carry one copy have a three-fold higher risk of Alzheimer’s than those with none. And those with two copies, as Tyrone carries, have 8- to 12-fold higher risks. Between 51 and 68 percent of them will develop the disease by the time they are 85. The risk is so large that some people who get their genomes analyzed (including James Watson, a co-discoverer of the DNA double helix) deliberately decide to redact their ApoE4 sequence. They’d rather not know.
Even if ApoE4 carriers manage to dodge Alzheimer’s, they aren’t out of the woods. Compared to the general population, they tend to have higher cholesterol levels, a higher risk of heart disease, and a faster pace of mental decline during old age.
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