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A longitudinal study of polysomnographic variables in patients with mild cognitive impairment converting to
Luca Carnicelli1, Michelangelo Maestri1, Elisa Di Coscio1
1Section of Neurology, Department of Clinical and Experimental Medicine, University of Pisa and Pisa University Hospital, Pisa, Italy.
Abstract:
The main condition at increased risk of dementia is considered to be mild cognitive impairment. Mild cognitive impairment has been defined as a transitional state between normal aging and dementia, of which it may represent a prodrome. The aim of our study was to evaluate whether sleep variables (both conventional and microstructural ones) in subjects with mild cognitive impairment correlate with conversion to dementia. Nineteen subjects with amnestic mild cognitive impairment (mean age 68.5 ± 7.0 years) and 11 cognitively intact healthy elderly individuals (mean age 69.2 ± 12.6 years) underwent ambulatory polysomnography for the evaluation of nocturnal sleep architecture and cyclic alternating pattern parameters. Amnestic mild cognitive impairment subjects were clinically and cognitively re-evaluated after 2 years, during routine follow-up, and further classified as amnestic mild cognitive impairment converters (that is, patients developing Alzheimer's disease, N = 11) and amnestic mild cognitive impairment non-converters. Compared with healthy elderly individuals, amnestic mild cognitive impairment showed disrupted sleep with decreased rapid eye movement sleep, cyclic alternating pattern rate and cyclic alternating pattern slow-wave-related phases (A1 index). Standard sleep architecture analysis did not show significant differences between the two subgroups of amnestic mild cognitive impairment, whereas cyclic alternating pattern analysis showed that cyclic alternating pattern rate, A1 index and A3 index are significantly reduced in converters compared with non-converters. Our data confirm that in amnestic mild cognitive impairment subjects there is a sleep impairment, particularly when considering more refined sleep parameters and that sleep variables at baseline are different among converters versus non-converters at the 2-year follow-up. Specific sleep alterations might represent potential further biomarkers for the diagnosis and prognosis of early-phase cognitive impairment.
Insights
Mild cognitive impairment (MCI) disrupts sleep. Specific sleep changes, particularly cyclic alternating pattern (CAP) alterations, predict conversion to Alzheimer's disease in MCI patients.
Area of Science:
- Neuroscience
- Sleep Medicine
- Gerontology
Background:
- Mild cognitive impairment (MCI) is a transitional state between normal aging and dementia.
- Identifying predictors of dementia conversion in MCI is crucial for early intervention.
Purpose of the Study:
- To investigate the correlation between sleep variables and dementia conversion in individuals with amnestic MCI.
- To evaluate both conventional and microstructural sleep parameters as potential biomarkers.
Main Methods:
- Ambulatory polysomnography was used to assess nocturnal sleep architecture and cyclic alternating pattern (CAP) parameters in 19 amnestic MCI subjects and 11 healthy controls.
- Subjects were followed for 2 years to classify MCI converters (developing Alzheimer's disease) and non-converters.
Main Results:
- Amnestic MCI subjects exhibited disrupted sleep compared to controls, with reduced rapid eye movement (REM) sleep, CAP rate, and A1 index.
- While standard sleep architecture showed no significant differences between MCI subgroups, CAP analysis revealed significantly lower CAP rate, A1 index, and A3 index in converters versus non-converters.
Conclusions:
- Sleep impairment is evident in amnestic MCI, especially when considering advanced sleep parameters.
- Specific sleep alterations, particularly within CAP analysis, may serve as valuable biomarkers for diagnosing and predicting the prognosis of early-stage cognitive impairment and dementia conversion.