SAN ANTONIO, TEXAS—Peripheral neuropathy may cause instability and a high percentage of falls in the elderly, according to a study presented at the 60th Annual Scientific Sessions of the American Diabetes Association. However, a simple clinical test may identify patients with peripheral neuropathy, said lead investigator Aaron Vinik, MD, PhD.

In addition to age and diabetes, neuropathy may also affect balance, said Dr. Vinik, Director of the Strelitz Diabetes Research Institute and Professor of Medicine, Anatomy, and Pathology at the Eastern Virginia Medical School in Norfolk. "We know that about a third of people over the age of 65 fall each year and that 5% or more of the time this leads to a fracture," said Dr. Vinik. The cost of these fractures has been estimated to be about $12 billion each year, he said.

The researchers' goal was to "test the hypothesis—in a very well-defined patient population—that the loss of balance and coordination was due not simply to age [or] diabetes, but also to … nerve damage." They compared the balance of four groups of subjects: 18 normal, healthy controls between ages 20 and 40; 12 normal, healthy subjects between ages 70 and 79; 13 elderly diabetic subjects with no symptoms of neuropathy; and 14 elderly diabetic subjects with symptomatic peripheral neuropathy. Various tests were used, including standardized neurologic exams, nerve conduction studies of the peroneal nerves, quantitative sensory tests, and quantitative isometric tests of plantar and dorsiflexion strength. Standardized functional tests—the tandem stand, the one-foot stand, a timed-balance walk, a two-minute walk, and timed alternating foot tapping—were used to assess balance, gait, and coordination.

For subjects with diabetic neuropathy, the neurologic exam scores, nerve conduction amplitudes, quantitative sensory tests of vibration, and plantar and dorsiflexion strength revealed significant impairment. Although performance of the tandem stand did not appear to correlate with age, younger subjects had higher scores for all other tests of balance, and those with symptomatic diabetic neuropathy scored significantly worse on those tests. The researchers also found that balance tests, particularly the tandem stand, correlated significantly with conduction, amplitude, strength, and pressure sensation.

"These findings provide strong support for the hypothesis that neuropathy profoundly affects lower extremity physical function independently of age and diabetes," the researchers concluded. "The tandem-stand balance test provides the clearest evidence of this effect because it is impaired only in patients with neuropathy, [it] correlates with neurologic function, and it is not affected by the aging process. As a consequence, patients with neuropathy may be at increased risk of lower extremity disability and falling due to neuropathy-associated impairments."

According to Dr. Vinik, the percentage of women who show evidence of neuropathy by age 65 is "fairly alarming." An assessment of 894 participants in the Women's Health and Aging Study indicated that 58% of the women showed evidence of neuropathy by age 65. The tests used to rate peripheral neuropathy in that study included vibration perception threshold (which measures large-fiber function), usual- and fast-paced walking over a four meter course, and the ability to complete semitandem and tandem stands.

"If you looked at the continuum of vibration perception threshold, there was a progressive decline with age above 65; but above 85, there was a catastrophic decline," reported Dr. Vinik. The decline in nerve function, he added, correlated most strongly with loss of lower extremity strength and the loss of the ability to do a tandem stand.

"From a clinical standpoint, I think we've now developed a very simple tool that can be used by any clinician anywhere. To find a person at risk for [peripheral neuropathy] doesn't require doing a bone density test. You're just required to get them into your clinic, have them put one foot behind the other, and see if they can stand for 30 seconds," Dr. Vinik explained. He noted that people who cannot stand with one foot behind the other are less stable and are therefore at an increased risk of falling.

Two thirds of the older population cannot complete the tandem stand, Dr. Vinik noted. "People like that should be strongly encouraged to do balance training and strength training," he advised; "and that's not a very complicated thing to do, because earlier studies showed that older people can still improve their balance and strength with a little bit of training. I think that's a good health care precautionary measure," he concluded.

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