"Other researchers have suggested that polio is a more aggressive condition later in life, but we've actually found it to be relatively benign," says Eric Sorenson, M.D., Mayo Clinic neurologist and lead study researcher. "Our results suggest that polio survivors may not age any differently than those in the normal population -- they're not doing too badly compared to their peers. This tells us that the cause for the decline in muscle strength in polio survivors may be aging alone."
Polio is a contagious, viral illness that peaked in the United States in 1952, when 3,000 people died of the disease. Mass immunizations in the mid-1950s began to slow the spread of the disease, and the last case of polio not caused by a vaccine occurred in the United States in 1979. The three major types of polio include spinal polio, a paralytic polio that attacks nerve cells in the spinal cord; bulbar polio, in which the virus attacks motor neurons in the brainstem; and bulbospinal polio, a combination of spinal and bulbar polios. The effects of polio run the gamut from a complete return to normal function to paralysis of limbs to acute death. Following the illness, most patients are worried about their long-term prognoses, according to Dr. Sorenson.
To conduct this study, the researchers randomly selected a group of 50 polio survivors from the general population of Olmsted County, home of Mayo Clinic, and followed them for 15 years. The average age of participants at the study's start was 53, and the patients were an average of 40 years past their childhood experience with polio. The researchers measured strength and loss of neurons at the beginning of this period, and then again five a