researchers reported in Annals of Internal Medicine.
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The findings do not necessarily mean that doctors should implement broader screening for peripheral neuropathy at this time, however, the investigators said.
“Doctors don’t typically screen for peripheral neuropathy in persons without diabetes,” senior author Elizabeth Selvin, PhD, MPH, professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, Baltimore, said in an interview.
“Our study shows that peripheral neuropathy – as assessed by decreased sensation in the feet – is common, even in people without diabetes,” Dr. Selvin explained. “It is not yet clear whether we should be screening people without diabetes since we don’t have clear treatments, but our study does suggest that this condition is an underrecognized condition that is associated with poor outcomes.”
Patients with diabetes typically undergo annual foot examinations that include screening for peripheral neuropathy, but that’s not the case for most adults in the absence of diabetes.
“I don’t know if we can make the jump that we should be screening people without diabetes,” said first author Caitlin W. Hicks, MD, assistant professor of surgery, division of vascular surgery and endovascular therapy, Johns Hopkins University, Baltimore. “Right now, we do not exactly know what it means in the people without diabetes, and we definitely do not know how to treat it. So, screening for it will tell us that this person has this and is at higher risk of mortality than someone who doesn’t, but we do not know what to do with that information yet.”
Nevertheless, the study raises the question of whether physicians should pay more attention to peripheral neuropathy in people without diabetes, said Dr. Hicks, director of research at the university’s diabetic foot and wound service.
Heightened risk
To examine associations between peripheral neuropathy and all-cause and cardiovascular mortality in U.S. adults, Dr. Hicks and colleagues analyzed data from 7,116 adults aged 40 years or older who participated in the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2004.
The study included participants who underwent monofilament testing for peripheral neuropathy. During testing, technicians used a standard 5.07 Semmes-Weinstein nylon monofilament to apply slight pressure to the bottom of each foot at three sites. If participants could not correctly identify where pressure was applied, the test was repeated. After participants gave two incorrect or undeterminable responses for a site, the site was defined as insensate. The researchers defined peripheral neuropathy as at least one insensate site on either foot.
The researchers determined deaths and causes of death using death certificate records from the National Death Index through 2015.
In all, 13.5% of the participants had peripheral neuropathy, including 27% of adults with diabetes and 11.6% of adults without diabetes. Those with peripheral neuropathy were older, were more likely to be male, and had lower levels of education, compared with participants without peripheral neuropathy. They also had higher body mass index, were more often former or current smokers, and had a higher prevalence of hypertension, hypercholesterolemia, and cardiovascular disease.
During a median follow-up of 13 years, 2,128 participants died, including 488 who died of cardiovascular causes.
The incidence rate of all-cause mortality per 1,000 person-years was 57.6 in adults with diabetes and peripheral neuropathy, 34.3 in adults with peripheral neuropathy but no diabetes, 27.1 in adults with diabetes but no peripheral neuropathy, and 13.0 in adults without diabetes or peripheral neuropathy.
Among participants with diabetes, the leading cause of death was cardiovascular disease (31% of deaths), whereas among participants without diabetes, the leading cause of death was malignant neoplasms (27% of deaths).
After adjustment for age, sex, race, or ethnicity, and risk factors such as cardiovascular disease, peripheral neuropathy was significantly associated with all-cause mortality (hazard ratio [HR], 1.49) and cardiovascular mortality (HR, 1.66) in participants with diabetes. In participants without diabetes, peripheral neuropathy was significantly associated with all-cause mortality (HR, 1.31), but its association with cardiovascular mortality was not statistically significant.
The association between peripheral neuropathy and all-cause mortality persisted in a sensitivity analysis that focused on adults with normoglycemia.