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Changes in sleep-wake timing accompany cerebral glucose hypometabolism and cognitive function



– Dysregulated sleep-wake cycles may be linked to cerebral glucose hypometabolism and subtle cognitive changes, both of which are early signs of Alzheimer’s disease–like neurodegeneration, according to a 2-year study of older Korean adults.

Dr. So-Yeon Jeon, Seoul (South Korea) National University Michele G. Sullivan/MDedge News

Dr. So-Yeon Jeon

The association was particularly strong in subjects who experienced delayed acrophase, the peak of the normal sleep-wake cycle, So-Yeon Jeon, MD, said at the Alzheimer’s Association International Conference. It’s not yet clear whether the changes are a risk factor for dementia or a prodromal sign of neurodegeneration, but even without full elucidation, the findings could have value as a signal of impending neurodegeneration, said Dr. Jeon of Seoul (South Korea) National University.

“Our findings suggest that delayed acrophase may be used as a predictor for the progression of Alzheimer’s-type neurodegeneration and cognitive decline in the near future in old individuals with diverse cognitive status,” she said. “But the relationship between circadian phases and neurodegeneration is complex and not yet well understood.”

The 24-month study comprised 215 elderly adults enrolled in the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE). They were a mean of 70 years old at baseline; 143 were cognitively normal, 40 had mild cognitive impairment, and 32 had Alzheimer’s dementia. Both at baseline and 2 years, everyone underwent a comprehensive neuropsychological assessment, amyloid PET brain imaging with Pittsburgh compound B, and an [18F]-fluorodeoxyglucose PET scan to determine brain glucose metabolic rate.

Before each assessment, the investigators measured sleep and circadian rhythms with 8 days of actigraphy. This assessed sleep variables (total sleep time, sleep latency, sleep efficiency, and wakefulness after sleep); rest-activity rhythm variables (midline estimated statistic of rhythm, amplitude, and acrophase), and some nonparametric values including interdaily stability, intradaily variability, and relative amplitude of sleep cycles. Subjects also completed sleep diaries during these periods.

The study’s main outcomes were 2-year changes in the Mini Mental State Exam (MMSE) score and in Alzheimer’s imaging biomarkers, including glucose metabolism and amyloid deposition. All analyses controlled for age, sex, Clinical Dementia Rating score, apolipoprotein E allele status, and baseline cognition.

At baseline, lower total sleep time was significantly associated with hypometabolism in areas associated with Alzheimer’s pathology as well as lower mean MMSE scores. Circadian variables showed no significant associations with these characteristics. However, the relative amplitude of circadian rhythm was significantly associated with hypometabolism and with lower MMSE score. There were no associations with brain amyloid load.

At 2 years, acrophase was associated with declines in cerebral glucose metabolism and further changes in the MMSE, even after the researchers controlled for the potential confounders. Delayed acrophase, although not associated with either metabolic rate or cognition at baseline, did significantly influence both at 2 years, suggesting a rapidly eroding clinical picture.

“Neurodegeneration over 2 years means the disease is progressing rapidly and subjects are likely to have tauopathies or other proteinopathy,” Dr. Jeon said. “These pathologies may either be resulting in delayed acrophase followed by neurodegeneration, or they may be prodromal symptoms of impending neurodegeneration. Whether they are early symptoms or early risk factors is not currently known, however. Two years is too short of a follow-up to determine these questions.”

Dr. Jeon had no financial declarations.

SOURCE: Jeon SY et al. AAIC 2019, abstract 33543.

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