1 Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
2 Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Massachusetts General Hospital, Brigham and Women's Hospital, and Harvard Medical School, Boston.
3 Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
4 Sean M. Healey & AMG Center for ALS at Massachusetts General Hospital, Boston.