In general, PPS is not life-threatening. The major exception are patients left with severe residual respiratory difficulties, who may experience new severe respiratory impairment.There have been no sufficient longitudinal studies on the prognosis of post-polio syndrome; however, speculations have been made by several physicians based on experience. Fatigue and mobility usually return to normal over a long period of time. The prognosis also differs depending upon different causes and factors affecting the individual. An overall mortality rate of 25% exists due to possible respiratory paralysis of persons with post-polio syndrome; otherwise, post-polio syndrome is usually non-lethal.^[1]