Author(s): Hideto Shinno, Ichiro Ishikawa, Nobuo Ando, Yoshihito Matsumura, Jun Horiguchi and Yu Nakamura
Objective: Mild cognitive impairment (MCI) refers to the clinical condition between normal aging and Alzheimer’s disease (AD). Heterogeneity in this entity has also been recognized, and an accelerated rate of progression to AD was documented in some individuals diagnosed with MCI. It is important for the early detection of and intervention for AD to determine the clinical subtype of MCI with a high risk of progression to AD. Studies have demonstrated that deceased glucose metabolism or regional cerebral blood flow in the posterior cingulate may be associated with a higher risk of such progression. The aim of this study was to investigate whether any polysomnography (PSG) variables support the prediction of progression from MCI to AD.
Methods: Twenty-four subjects with MCI were enrolled in this study. Clinical evaluation, cognitive screening tests, and PSG were carried out at the baseline. A diagnosis of MCI was made with standard criteria. Outcome measures were carried out to examine whether: 1) there was a significant cognitive decline, and 2) it progressed to AD according to the standard criteria for it. After a 2-year follow-up, subjects were divided into 2 groups. The MCI-AD group included subjects who progressed to AD, and the MCI-MCI group included those who did not meet the criteria for dementia. Basal PSG variables were compared between the groups.
Results: Nineteen subjects completed the study. Six subjects (32%) progressed to AD within 2 years. Subjects in the MCI-AD group showed a shorter stage REM sleep (p=0.043), and a reduced REM density (p=0.043) at the baseline.
Conclusion: Subjects who progressed to AD demonstrated altered REM sleep variables, yet they did not meet the criteria for clinically probable AD in the examination period. We consider that these properties may be associated with a higher risk of progression from MCI to AD.
