Original ArticlePrevalence and clinical characteristics of restless legs syndrome in diabetic peripheral neuropathy: comparison with chronic osteoarthritis
Introduction
Restless legs syndrome (RLS), also called Willis-Ekbom disease, is a neurologic disease that is characterized by unpleasant and at times painful sensations in the legs associated with an overwhelming urge to move the legs (i.e., akathisia) [1]. Like RLS, peripheral neuropathy causes pain in the legs and is associated with an increased prevalence of RLS in some studies [2], [3], [4], [5], [6], [7], [8]. This finding is indicative of a correlation between peripheral neuropathy and RLS. However, there are two significant issues of putative relations between RLS and peripheral neuropathy. First, the differential diagnosis can be difficult. The prevalence of RLS in patients with peripheral neuropathy ranges from 5.2% to 30% [2], [3], [4], [7], [8]. Although this wide variation may reflect population differences, it also could result from differing degrees of care in making this somewhat difficult diagnosis of RLS with peripheral neuropathy. Second, leg pain itself may engender or exacerbate RLS; that is, the association between peripheral neuropathy may be related to leg pains and not to the neuropathy. The presence of leg pain also may complicate the diagnosis and may be the primary reason for problems regarding the reliability of RLS diagnosis. Our study sought to address both of these questions. First, we compared a clinical face-to-face diagnosis of RLS based on the four essential criteria to a structured interview diagnosis (the Hopkins Telephone Diagnosis Interview [HTDI]), which emphasizes differential diagnoses [9], [10]. Second, we aimed to assess the effects of leg pains. Our study used this same diagnostic procedure to evaluate RLS prevalence in patients with other conditions that produced leg pains with minimal systemic neurologic or immunologic complications (i.e., osteoarthritis [OA]).
Our study has three primary a priori hypotheses: (1) prevalence of RLS with peripheral neuropathy will be significantly less when the diagnosis is determined by a validated structured diagnostic interview than by the usual clinical interview evaluating only the four RLS diagnostic criteria; (2) the difference between RLS diagnosis by clinical ascertainment of the four essential criteria vs the validated structured interview will be greater for DPN than OA patients; and (3) prevalence of RLS when diagnosed using the structured interview will be greater for patients with peripheral neuropathy than those with leg pains from OA controlling for effects of gender and age. Sleep, pain, and quality of life (QoL) scales also were used to explore the status of these clinical features for RLS patients with peripheral neuropathy vs those with leg pains from OA.
Section snippets
Methods
Our study was a prospective case-control study, which was approved by the institutional ethics committee of a local hospital. For our study, evaluations were limited to peripheral neuropathy occurring with diabetes mellitus (DM) and of OA primarily involving the knee. Between June 2009 and August 2011, a consecutive series of consenting patients with diabetic peripheral neuropathy (DPN) or with OA of the knees were identified through the University Hospital Endocrinology and Rheumatology
Overall DPN and OA population characteristics
Table 1 presents the comparison of the clinical characteristics and questionnaire results for the DPN and OA population surveyed. The mean age of the DPN patients was significantly younger than the OA group (mean ± standard deviation [SD], 62.91 ± 10.95 years and 67.67 ± 8.67 years; P < .001) and consisted of fewer women (53.8% vs 83.6%; P < .001). The reported level of pain in the OA group as indicated by all the components of the McGill Pain inventory and VAS was significantly higher than in the DPN
Discussion
We confirmed our first hypothesis that the usual diagnosis of RLS for patients with DPN, which was based on a face-to-face clinical interview ascertaining the four clinical symptoms, had a low positive predictive value for RLS diagnosis by a validated structured interview (HTDI) that asked about the four diagnostic criteria in more detail and excluded RLS mimics. We also confirmed our second hypothesis that the positive predictive value of the usual clinical diagnosis would be much less for
Conflict of interest
The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2013.09.013.
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