Identification of circadian-sensitive brain structure and its role in cognitive impairment and dementia

Circadian disruption has been suggested to induce cognitive impairment and dementia. It remains unknown which brain structures are involved in the pathology.

To investigate which specific brain structure alterations are associated with dementia and cognitive impairment induced by circadian disruption.

Circadian disruption was represented by two accelerometer-derived circadian variables, composite phase deviations (CPD) and relative amplitude (RA), separately reflecting circadian disruption in timing and amplitude. The outcomes include brain structures (139 imaging-derived phenotypes), cognitive test performances (seven cognitive tests) and dementia (all-cause dementia, Alzheimer's disease, vascular dementia (AD/VD) and non-AD/VD dementia). Association analysis was used to explore the relationships between circadian disruption and brain structure alterations, cognitive test performances and dementia. Mediation analysis was conducted to investigate which brain structure alterations mediated the cognitive impairment and dementia caused by circadian disruption.

A total of 88 461 participants (57% female, 62.0±7.8-year old) were included. CPD and RA correlated with substantially different brain structures. All CPD-related brain structures were located in the cerebrum, whereas most RA-related brain structures were located in the cerebellum. Furthermore, only the CPD-related brain structures, including the hippocampus and thalamus, exhibited significant mediation effects accounting for up to 8.6% of the risk for dementia and 13.5% of the risk for cognitive impairment.

Circadian disruption is associated with brain structural alterations involving dementia and cognitive impairments.

These results provide a novel insight into the mechanism underlying circadian disruption-induced neurological disorder and may propose potential preventive strategy.