Metabolic syndrome components linked to polyneuropathy

By Marilynn Larkin

NEW YORK (Reuters Health) - Distal symmetric polyneuropathy (DSP) is common in patients with metabolic syndrome, regardless of their glycemic status, although the impact of various metabolic syndrome components is not clear, researchers report.

"While diabetes is by far the number-one cause (of DSP), enhanced glucose control is only marginally effective at reducing the incidence in patients with type 2 diabetes. One possible explanation for this small therapeutic effect is that other factors, such as the other components of the metabolic syndrome . . . may be significant contributors to nerve injury . . . (and) the underlying cause for some of the 30% of DSP patients currently labeled as idiopathic," they point out.

To determine the magnitude of the effect of metabolic syndrome and the precise components involved, the researchers first determined the prevalence of symptomatic DSP in a large prospective cohort study of individuals aged 70-79 at baseline, stratified by glycemic status and the number of additional metabolic syndrome components. DSP was defined as neuropathic symptoms plus at least one confirmatory test.

Analyses of data from 2,382 participants with neuropathy data revealed that 21% had diabetes, 29.9% had prediabetes, 52.8% had metabolic syndrome, and 11.1% had DSP. Stratified by glycemic status, DSP prevalence increased as the number of metabolic syndrome components increased. Diabetes (odds ratio 1.65) and baseline hemoglobin A1C (OR 1.42) were the only metabolic syndrome measures significantly associated with DSP.

"In concert with previous studies, we demonstrate that the prevalence of diabetes, MetS (metabolic syndrome), and DSP is incredibly high in even a well-functioning older population," the authors reported online March 10 in Diabetes Care. "As a result, any causal link between MetS and neuropathy, regardless of diabetes status, would have potential therapeutic implications for a large proportion of older adults."

Lead author Dr. Brian C. Callaghan of the University of Michigan told Reuters Health by email, "The key take-home message is that hyperglycemia is the most important risk factor for polyneuropathy, but that the metabolic syndrome also appears to play a role. Future studies are needed to determine which metabolic components besides hyperglycemia are important in the development of polyneuropathy so that we can target our therapies appropriately. Currently, we focus treatment on hyperglycemia, which is not enough to prevent polyneuropathy or its progression."

In an email comment to Reuters Health, Dr. Devin W. Steenkamp of Boston University School of Medicine observed, "This article reports on a relatively healthy elderly prospective cohort of individuals . . . and aims to shed some light on relevant clinical questions, such as why certain individuals with type 2 diabetes and distal polyneuropathy do not note improvement in their neuropathic symptoms with improved glycemic control. Do other associated features of the metabolic syndrome, independent of diabetes, contribute to neuropathy that may otherwise be regarded as 'idiopathic'"?

"The study used a strict definition of neuropathy, which is a significant strength, and the major weakness is that neurological exams were not performed but rather neuropathy symptoms were adjudicated through a questionnaire."

In Dr. Steenkamp's view, "The major take-home point is that metabolic syndrome components, individually and collectively, independent of glycemic status, are associated with DSP. The more components of the metabolic syndrome that are present, the more this risk seems to be, especially in an elderly population. However, diabetes is still the most common and significant independent contributor to neuropathy."

The National Institute on Aging, the National Institute of Nursing Research, and other organizations supported this research. One coauthor reported disclosures.

SOURCE: http://bit.ly/1pZOPsz

Diabetes Care 2016

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