Not always, it strikes some in their 40s and 50s.

Okay, but wait. All this really translates into is "getting" the disease 2-6 years earlier than you actually get it. From an insurance standpoint, if you are insured (through your employer or otherwise) when you get the test, it would be covered as a new disease. The only way you would become uninsurable is if you lost your insurance after being tested/diagnosed, and were also unable to get on another group policy through a new employer. Which is not a great situation, to be sure, but it's what already happens now to millions of people with pre-existing conditions.* This blood test is not the same as being able to tell from birth all the diseases and conditions you will eventually get.

*And for the record, many states do already have government insurance programs for people who are uninsurable because of pre-existing conditions. In Texas they call it the "High Risk Pool," and my friend's 5-year-old diabetic daughter is on it.

The wife of a friend this last month was diagnosed with Alzheimer’s. After a few weeks spent with a psychologist, it was discovered her medication was creating Alzheimer's symptoms. A problem known to exist with those drugs but (apparently) unknown to her doctor who diagnosed Alzheimer’s. Her prescriptions were changed. He says he finally has his wife back.