Validity of the medical outcomes study sleep scale in patients with painful diabetic peripheral neuropathy in Korea

AIMS/INTRODUCTION Sleep disturbances caused by painful diabetic neuropathy (PDN) might have substantial impacts on the multifaceted aspects of PDN, including quality of life. There are no convincing data on the validation or reliability of sleep problem measurements in patients with PDN in Korea. This large population-based cross-sectional study examined psychometric properties of the Medical Outcomes Study (MOS) Sleep Scale in patients with PDN in Korea. MATERIALS AND METHODS Measurements of patient-reported outcomes (Brief Pain Inventory-short form, MOS Sleep Scale and EuroQoL Health [EQ-5D]) were documented. PDN was diagnosed if the average daily pain intensity was ≥4 based on the visual analog scale or if patients were taking medication for their current pain. RESULTS There were 577 patients with PDN (41.6% with diabetic peripheral neuropathy). The internal consistency of reliability for the MOS Sleep Scale was 0.80 as measured by Cronbach's alpha. The extent to which multiple items in a dimension were intercorrelated and formed a dimension measuring the same underlying concept (Pearson's correlation coefficient) ranged from 0.24 to 0.71 (all P < 0.001). Each item of the MOS Sleep Scale was significantly correlated with the average pain score and the pain interference score (Pearson's correlation coefficients ranged from 0.20 to 0.28 and from 0.29 to 0.40, respectively; all P < 0.001). The correlations between the EQ-5D index and the MOS Sleep Scale ranged from -0.27 to -0.31 (all P < 0.001). CONCLUSIONS The MOS Sleep Scale showed good reliability in the evaluation of PDN in Korean type 2 diabetic patients.