ABSTRACT
One in four people worldwide suffer some form of neurodegenerative disorder. The World
Health Organization estimates that there are currently four million people worldwide with
Parkinson’s disease (PD), 37 million with Alzheimer’s disease (AD) (4.5 million in the
United States), and 5.5 million die each year as a result of cerebrovascular events. In
the United States, more than 50 million people are affected by various central nervous
system (CNS) diseases. Each year, 11,000 people sustain spinal cord injury, adding to
the 400,000 or so already affected. Two million people have been disabled by head injuries
with 1.5 million people a year suffering traumatic brain injury (TBI), adding to the 5.3
million already living with disabilities resulting from TBI (https://www.who.int). With an aging global population, the number of people with neurodegenerative and cerebrovas-
cular conditions continues to grow, as does the cost to the health service.
