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About three to six in every 100,000 people worldwide, or approximately 20,000 Americans, have PSP—making it much less common than Parkinson's disease (another movement disorder in which an estimated 50,000 Americans are diagnosed each year). Symptoms of PSP begin on average after age 60, but may occur earlier. Men are affected more often than women.My mother was in her late 70's when symptoms first appeared and diagnosed in her 80's.