Parkinson disease risks: correctly identifying environmental factors for a chronic disease.

Parkinson disease (PD) is now the world's fastest growing brain disease; however, the factors underlying this rise are unclear. The past 25 years has witnessed a vast expansion in our understanding of the genetics of PD, but few individuals with PD carry one of the major known genetic risk factors. Environmental factors, including individual (e.g., medications) and ambient (e.g., pollutants), may contribute to this rise. In this issue of the JCI, Sasane et al. examined the risk of PD associated with medications commonly used to treat benign prostatic hypertrophy. In contrast with previous studies, certain α1 receptor antagonists failed to lower PD risk. Rather, the commonly used comparator drug, tamsulosin, increased PD risk. This finding highlights the importance of selecting comparator groups to correctly identify risk factors. Future studies to address the rise of PD with emphasis on both individual as well as the understudied ambient environmental factors are warranted.