SAN DIEGO – Polyneuropathy affects an estimated 2.1% of the general population and about 10% of older adults, results from a large analysis demonstrated.
In addition, "surrogate markers of disability such as medication use, complications, and disabling symptoms seem to indicate that polyneuropathy confers significant disability," Dr. Christopher J. Klein said in an interview prior to the annual meeting of the American Academy of Neurology, where the research is scheduled to be presented March 21 by Dr. E. Matthew Hoffman, a PGY-2 resident in the neurology department at the Mayo Clinic, Rochester, Minn. "As the U.S. population ages and diabetes rates continue to rise, the disease burden of polyneuropathy will only increase."
Dr. Klein, of the division of peripheral nerve diseases in the neurology department at the Mayo Clinic, said that population-based epidemiologic studies of polyneuropathy and peripheral nerve diseases are lacking in terms of sampling completeness, population size, and generalizability. "As far as we can determine, there are no population-based estimates of disability related to polyneuropathy," he said.
To ascertain the disease burden of polyneuropathy, he and his associates evaluated data from the Rochester Epidemiology Project (REP), which links the population of Olmsted County, Minn., to electronically retrievable medical records of virtually all residents. The REP census generally has exceeded the U.S. Census since 1970, making population sampling very complete, Dr. Klein said.
In their analysis, the researchers studied 138,420 Olmsted County residents who received health care between 2006 and 2010, gathering five age- and gender-matched controls for each case with an ICD-9 code that implied a diffuse polyneuropathy, such as 337.0. They excluded 11,494 cases of isolated mononeuropathies, plexopathies, and radiculopathies.
More than half of the studied population (56%) had comprehensive neurologic examinations available by certified neurologists with retrievable neurology sheets documenting motor, reflex, and sensory deficits; gait difficulties; and other components of a comprehensive neurologic examination. Electronically retrievable nerve conduction studies were also available in 43% of the studied population. Information on medications, complications related to polyneuropathy, and answers to survey questions about disabling symptoms were extracted for cases and controls as surrogate markers to quantify functional disability.
Dr. Klein reported that 2,897 cases of polyneuropathy were identified, which translated into a prevalence of 2.1% for the entire population for the 5-year period. The prevalence rose with age and peaked in the eighth decade of life for both men (11.2%) and women (7.9%), which meant that about 10% of elderly overall were affected. Fifty percent of the polyneuropathy cases were idiopathic, followed by diabetic (38%), inflammatory (5%), hereditary (3%), toxic (3%), and other (1%).
The researchers observed many statistically significant increases in surrogate markers of disability, compared with the matched controls, including an eightfold increase in pain medication use; a fivefold increase in lower-limb ulcers; and up to a threefold increase in difficulties in gait, need for gait aids, and difficulties climbing stairs. This extent of witnessed surrogate marker disabilities is similar to what is observed with other major medical problems, said Dr. Klein, who is also co-editor of the Journal of the Peripheral Nervous System.
One limitation of the analysis, he noted, was that polyneuropathy cases were identified from ICD-9 codes. "Therefore, for most patients, symptomatic presentation is most likely and asymptomatic cases may not be documented, possibly leading to underestimation," Dr. Klein said.
The study was supported by the National Institute of Neurological Disorders and Stroke, the National Institute on Aging, and the Mayo Foundation. Dr. Klein reported having no relevant financial disclosures.