Abstract
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Objectives Hypometabolism on FDG PET is a downstream marker of neuronal injury and is documented as a useful biomarker for predicting mild cognitive impairment (MCI) due to Alzheimers disease (AD) (1). Recent studies have shown that sleep disturbance is linked to amyloid in brain areas affected by AD and occurs in around two-thirds of patients with MCI (2). In this study, we evaluated the association of hypometabolism on Fluorine-18 Fluorodeoxyglucose (F-18 FDG) Positron Emisssion tomography (PET/CT) with the sleep architecture in patients with MCI. This was an exploratory analysis as a part of our ongoing study evaluating F-18 FDG-PET and sleep architecture in MCI-converters Vs non-converters.
Methods Thirty-six patients with MCI [Mean age=66.2 ± 9.4 (SD) years, M:F=27:9] underwent detailed neurological and neuropsychological assessment, which included Mini Mental State examination (MMSE), Geriatric depression scale (GDS) and Epworth sleepiness scale score (EPSS). Each patient underwent overnight polysomnography in the sleep laboratory and F-18 FDG PET/CT within an interval of 10-14 days. Sleep architecture measures included wake after sleep onset (WASO), % slow wave sleep (SWS), arousal index (AI). and sleep efficiency. The association of hypometabolism (in Alzheimer related regions) with these sleep parameters was tested using the Fischers exact test (STATA).
Results A total of 25 % patients (9/36) exhibited hypometabolism in AD related territories on PET and 44 % (16/36) had decreased sleep efficiency on PSG. Sleep parameters were scored using normative values reported in literature (3,4). All patients with hypometabolism on PET had abnormal WASO (p= 0.001), 30 % had abnormal % SWS (p=0.65), 90 % had abnormal AI (p=0.39), and 80 % had abnormal sleep efficiency (p=0.01). These observations suggest a statistically significant association of hypometbolism on PET with abnormal WASO and sleep efficiency.
Conclusions Hypometabolism on FDG PET is associated with deranged sleep patterns in MCI patients. The combination of FDG-PET with sleep architecture may serve as effective markers for progression of cognitive decline in MCI patients and offers a promising approach to assess individual prognosis in MCI patients.