Mild Impairments in Cognitive Function in the Elderly with Restless Legs Syndrome

Kim, Eun Soo; Yoon, In Young; Kweon, Kukju; Park, Hye Youn; Lee, Chung Suk; Han, Eun Kyoung; Kim, Ki Woong

Abstract

OBJECTIVES
Cognitive impairment in restless legs syndrome (RLS) patients can be affected by sleep deprivation, anxiety and depression, which are common in RLS. The objective of this study is to investigate relationship between cognitive impairment and RLS in the non-medicated Korean elderly with controlling for psychiatric conditions. METHOD: The study sample for this study comprised 25 non-medicated Korean elderly RLS patients and 50 age-, sex-, and education-matched controls. All subjects were evaluated with comprehensive cognitive function assessment tools-including the Korean version of Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD-K), severe cognitive impairment rating scale (SCIRS), frontal assessment battery (FAB), and clock drawing test (CLOX). Sleep quality and depression were also assessed with Pittsburgh sleep quality index (PSQI) and geriatric depression scale (GDS).
RESULTS
PSQI and GDS score showed no difference between RLS and control group. There was no significant difference between two groups in nearly all the cognitive function except in constructional recognition test, in which subjects with RLS showed lower performance than control group (t=-2.384, p=0.02). Subjects with depression (GDS> or =10) showed significant cognitive impairment compared to control in verbal fluency, Korean version of Mini Mental Status Examination in the CERAD-K (MMSE-KC), word list memory, trail making test, and frontal assessment battery (FAB). In contrast, no difference was observed between subjects who have low sleep quality (PSQI>5) and control group.
CONCLUSIONS
At the exclusion of the impact of insomnia and depression, cognitive function was found to be relatively preserved in RLS patients compared to control. Impairment of visual recognition in RLS patients can be explained in terms of dopaminergic dysfunction in RLS.