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Diabetic Peripheral Neuropathy Linked to Deterioration in Muscle Strength

Sep 21, 2019
 
Editor: Steve Freed, R.PH., CDE

Author: Amber Satz, PharmD Candidate, LECOM School of Pharmacy

Studies show a link between diabetic peripheral neuropathy and sarcopenia, which increases frailty and subsequent mortality.

Persistent hyperglycemia from diabetes causes great damage throughout the body, with particular destruction to the vascular system. The result of such damage from type 1 and type 2 diabetes is macrovascular complications such as coronary artery disease, peripheral artery disease and stroke, and microvascular complications including diabetic peripheral neuropathy (DPN), diabetic nephropathy and diabetic retinopathy. Each microvascular complication is proportional to the extent and duration of hyperglycemia and some patients may have a genetic predisposition to developing certain complications.

Diabetic peripheral neuropathy is associated with significant morbidity and mortality. In addition to symptoms of pain and numbness, DPN can lead to issues as severe as amputation and death due to foot ulceration or injury. Additionally, DPN may contribute to a decrease of muscle quality including mass and functionality, or sarcopenia, leading to frailty in patients with diabetes. As frailty increases the risk of mortality even further, it is of great interest to understand the relationship between DPN and muscle quality.

Studies have shown that decreased lower muscle strength is associated with DPN in patients with both type 1 and type 2 diabetes. A new study looked at the association between DPN and muscle function using handgrip strength (HGS) in people with type 2 diabetes. 230 participants with a mean age of 56 were evaluated for diagnoses of DPN based on the Michigan Neuropathy Screening Instrument (MNSI) protocol which involves two assessments: a 15-item self-administered questionnaire (MNSI-Q) and a physical examination of the lower extremity (MNSI-PE).  Muscle strength was measured using a digital grip strength dynamometer (GRIP-D).

Results reported 69 of 230 participants were diagnosed with DPN according to MNSI scores. An association between HGS and DPN was seen in men only. HGS was lower in men with DPN than in those without DPN (p=0.036). Additional data collected indicated that higher HbA1c levels, more insulin use, higher incidence of retinopathy and coronary artery disease were associated with participants with DPN.

It is interesting to note that women with DPN in this study did not show a decrease in muscle function. The reasoning behind this could be that DPN was diagnosed mostly by the questionnaire method and therefore there is room for subjective discrepancies in reporting. Women may have been more likely to be diagnosed than men with the MNSI questionnaire. Another reason for the divide in gender could be explained by a previous observational study which showed that women’s’ muscle function tends to decline acutely above the age of 55 years old whereas men’s muscle function declines slowly. Also, hormone replacement therapy can influence muscle composition in postmenopausal women.

This study had a small population size and was designed as a cross-sectional observational study. Because of the nature of the design, a causal relationship between DPN and muscle function cannot be identified. Also, the effects from differing treatments, comorbidities and glycemic control could not be factored in through this study. Further research is needed to better understand the long-term outcomes associated with DPN and whether neuropathy precedes muscle function decline.

DPN commonly goes unnoticed, therefore it is important for clinicians to recognize the manifestations of DPN. As patients age, moderate muscle deterioration can occur; in patients with diabetes and DPN, this deterioration can be tremendous and contribute to extreme frailty in elderly patients. Frailty can limit patients’ mobility and ability to take care of themselves leading to increased mortality, the incidence of depression, medical costs and worsened impact on families. It is of great importance for clinicians to understand the relationship between DPN and muscle weakening or deterioration so that they can identify high-risk patients and provide appropriate treatment and information to patients.

Practice Pearls:

  • Multiple studies including one new observational study have identified the impact of diabetic peripheral neuropathy on sarcopenia, muscle mass and functionality.
  •  It is important to identify patients with DPN, with or without symptoms, due to high risk for increased complications including sarcopenia and frailty.
  •  Further longitudinal studies are needed to establish causality between DPN and muscle deterioration.

Oh, Tae Jung, et al. “Association between Deterioration in Muscle Strength and Peripheral Neuropathy in People with Diabetes.” Journal of Diabetes and Its Complications, vol. 33, no. 8, 2019, pp. 598–601., doi:10.1016/j.jdiacomp.2019.04.007.

Fowler, Michael J. “Microvascular and Macrovascular Complications of Diabetes.” Clinical Diabetes, American Diabetes Association, 1 Apr. 2008, clinical.diabetesjournals.org/content/26/2/77.

Amber Satz, PharmD Candidate, LECOM School of Pharmacy