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The lipid-lowering drugs statins and fibrates also may lower the risk of peripheral neuropathy—nerve damage in the hands and feet—in patients with diabetes, suggests a large Australian observational study. Each drug type appears independently linked to reduced neuropathy risk, says lead researcher Timothy Davis, MD, PhD, who presented the results at the American Diabetes Association's 67th Scientific Sessions, held June 22–26 in Chicago.
"The relative risk reduction we see in diabetic neuropathy is around that we see in cardiovascular disease [CVD] prevention using statin therapy," says Davis, a professor of medicine at University of Western Australia (UWA) in Perth, who notes an independent UWA trust financed the research. The study indicates statins may lower patients' neuropathy risk by roughly a third, and that fibrates may drop patients' neuropathy risk by almost half.
"We believe we've serendipitously found an interesting effect that supports statin and fibrate use, in addition to the conventional [CVD] indication," says Davis.
The results are noteworthy because currently no U.S. drugs are approved for neuropathy treatment or prevention, only for associated pain, says longtime neuropathy researcher Aaron I. Vinik, MD, PhD, director of the Diabetes Research Institute at The Strelitz Diabetes Institutes at Eastern Virginia Medical School in Norfolk. Peripheral neuropathy—which involves pain, numbness, tingling, weakness, and inability to determine different textures—occurs in at least half of diabetes patients, and the condition leads to 96,000 amputations annually in the U.S., Vinik says.
REDUCED RISK
In Davis's study, researchers followed 531 participants in a cross-sectional arm of the Fremantle Diabetes Study1 for 5 years. Most of the patients had type 2 diabetes, and they were, on average, age 64 at the beginning of the study. Roughly half were male, and most of them—400—were free of peripheral neuropathy at baseline.
Most patients in the study sample were prescribed the statin simvastatin (Zocor, Merck). The remaining patients took pravastatin (Pravachol, BristolMyers Squibb) and atorvastatin (Lipitor, Pfizer). The fibrate prescribed was predominantly gemfibrozil (Lopid, Pfizer), though some patients took fenofibrate (TriCor, Abbott). Over 5 years, patients' use of fibrates increased from 3.5% to 10.4%, and their use of statins increased from 6.8% to 36.5%. Meanwhile, almost two-thirds of those who initially had no neuropathy developed the condition, as diagnosed via the Michigan Neuropathy Screening Instrument (see "FYI").
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But those taking statins or fibrates were significantly less likely to develop peripheral diabetic neuropathy. Specifically, those on statins showed a 35% relative risk reduction, and those on fibrates showed a 48% relative risk reduction—strong buffering effects, Davis says.
However, Davis acknowledges the limits of the study's observational methodology. The researchers didn't specifically track the drugs' effects against placebo, as in a carefully controlled clinical trial.
Davis also notes that his findings counter some anecdotal reports of increased neuropathy in diabetes patients on statins, but square with results of the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study of close to 10,000 patients, which linked fibrate use with macro- and microvascular benefits (DOC News, January 2006, page 1).2
THE MECHANISM QUESTION
In the current study, the neuropathy-buffering effect occurred independently of patients' glycated hemoglobin, diabetes duration, age, blood pressure, central adiposity, and other neuropathy risk factors. The researchers also found no association between patients' lipid-lowering and neuropathy results.
How, then, might the drugs lessen neuropathy risk? Davis says they possibly could reduce oxidative stress and accumulatation of the sugar alcohol sorbitol, which can cause nerve and eye damage in diabetes patients. But he cautions this is only speculation.
"It's our hypothesis," he says, "and it's yet to be
tested, that the drugs' protective effects are not mediated through their
effects on lipids, but through something else." 
Footnotes
The Michigan Neuropathy Screening Instrument involves a brief physical examination and a patient self-assessment of neuropathy. It is intended for use by primary care or other providers. More information is available at www.med.umich.edu/mdrtc/survey/index.html#mnsi.
References
2. Keech A, Simes RJ, Barter P, et al., for the FIELD study investigators: Effects of long-term fenofibrate therapy on cardiovascular events in 9,795 people with type 2 diabetes mellitus (the FIELD study): Randomised controlled trial. Lancet 366: 1849–1861, 2005.[Medline]
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