Changes in circadian RHYTHM in alzheimer disease and its morphological findings

Alzheimer Disease (AD) is the most common form of dementia in the elderly and with growing of aging population gains importance by means of raising individual disability and the costs of health and daily care settings. Sleep and circadian disruption is a frequently encountered entity in AD and a very common cause of institutionalisation of patients and difficulties in caring. The aim of this study is to investigate the relationship of cognitive performance, hypothalamic volume and sleep-wake habits mostly in early phase of the disease, compared to a control group, in the search of a neuroimaging biomarker availability. From September 2019 to July 2020, 20 patients (prodromal, mild and moderate AD) and 8 control were participated, however due to data availability, 12 patients and 5 control were included in statistical analysis. Study settings are composed of a brain MRI, an actigraphy measurement up to 7 days, neurpsychometric tests and sleep inquiries. In the results of our study, a statistically meaningfull change in hypothalamic volume is not observable in this small sample of population. The only statistically significant difference between groups is in the variable of minimum sleep onset latency which resulted longer in the patient group. Analysis between MCI and mild-moderate AD groups points to an increased minimum sleep efficiency by the increase of disease stage but no significant differences in maximum and average sleep efficiencies which necessitates further investigation. Another result is a tendecy to a better memory test scores with a longer total sleep time. It is also observed that increased sleep fragmentation indicates a worse executive cognitive function, whereas total sleep time measures indicate the reverse. The size of our sample is not sufficient to make general interpretations, however findings observed in our study support the fact that AD tends to cause sleep-wake rhythm disruption. Broader sample-sized studies are needed to demonstrate circadian rhythm disruption patterns in AD with a polisomnographic verification, and to detect a change in hypothalamic volume which is a quite small anatomic structure.