 A vaccine against polio has cut the numbers affected by the disease |
People who survive polio in childhood will not suffer further effects later in life, say US researchers. The Mayo Clinic team looked at 50 people who had had the disease as children and found most did not suffer any polio-related decline when older.
Polio has been wiped out in most places but remains a threat, particularly in India, Pakistan and Nigeria.
Experts said the Journal of the Peripheral Nervous System paper offered reassurance to polio survivors.
Polio is a contagious, viral illness which can attack nerve cells in the spinal cord or motor neurones in the brainstem. In some cases, it affects both.
People who contract the disease may not be left with any lasting effects - but polio can cause paralysis or even death.
It affected thousands of children across the world before widespread vaccination programmes were introduced in the 1950s and 60s.
Now, 98% of all cases are found in India, Nigeria and Pakistan.
Modest declines
People who have had polio worry about long-term effects.
In this study, researchers randomly selected a group of 50 polio survivors, with an average age of 53, from the area around the Mayo Clinic.
The researchers measured muscle strength, heart rhythm and nerve cell loss in the brain at the start of the study, and then carried out the same tests five and 15 years later.
It was found that people experienced only modest functional declines, in the same way that anyone in their sixties might.
Questionnaires filled in by the patients revealed most complained of progressive weakness during the time they were studied.
However, these symptoms did not correspond with their actual magnitudes of decline over time.
Instead, it was linked to the degree of residual weakness immediately following their polio infections.
'Years of stability'
Dr Eric Sorenson, who led the study, said: "Other researchers have suggested that polio is a more aggressive condition later in life, but we've actually found it to be relatively benign.
"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."
He added that the findings should be comforting to people worried about polio-related decline later in life.
"Though the likelihood is high that patients who have had childhood polio will complain of weakness later in life, they can expect years of stability without the need for major lifestyle modifications."
Joan Headley, executive director of the US organisation Post-Polio Health International, said: "The Mayo study is important because it follows people over many years, while other studies may represent just a snippet in time.
"The research emphasises that the polio survivors who are having the most problems now are those who had the greatest weakness during the acute poliomyelitis.
"That fact can be reassuring to those survivors who have heard a very disturbing message about the ravages of post-polio syndrome for all polio survivors."
However she said the fact that declines may be small, but could be noticed by individuals was important.
"That really is the crux of the matter for the members we serve.
"If you are that polio survivor, the new weakness can have a major impact on your day-to-day activities."
The research emphasises that the polio survivors who are having the most problems now are those who had the greatest weakness during the acute poliomyelitis 