Half to 80% of the brain cells that produce dopamine (the ones Parkinson’s disease targets) are already damaged or dead. But what if, in early Parkinson’s, these systems themselves become part of the problem? About half the DNA repair genes and nearly three-quarters of the stress response genes showed these complex temporal dynamics. And there’s the uncomfortable fact that not everyone in the prodromal group will necessarily convert to clinical Parkinson’s disease. More than 10 million people worldwide live with Parkinson’s disease, a number expected to more than double by 2050 as populations age.