An analysis by Scientific American shows a spike in stroke rates among U.S. millennials is occurring in the West and Midwest and in urban areas.

Why it matters: Mitchell Elkind, a stroke expert at Columbia University and New York-Presbyterian Hospital, told Scientific American that severe strokes in millennials are "a big problem because disability in people in their peak earning years can severely impact their families and future lives."

Geographic trends: Strokes in the western region of the U.S. increased by 70% from 2003 to 2012, while the Midwest saw a 34% climb in the same years. The highest rates are still in the South where 10 cases are responsible for every 10,000 people aged 18- to 34-years old who are hospitalized.

What's happening: President of the American Academy of Neurology, Ralph Sacco, suggested contributing factors could be drug use, obesity, physical inactivity and diabetes.