Associations between accelerometer‐measured circadian rest‐activity rhythm, brain structural and genetic mechanisms, and dementia

Aim Knowledge of how circadian rhythm influences brain health remains limited. We aimed to investigate the associations of accelerometer‐measured circadian rest‐activity rhythm (CRAR) with incident dementia, cognitive dysfunction, and structural brain abnormalities in the general population and underlying biological mechanisms. Methods Fifty‐seven thousand five hundred and two participants aged over 60 years with accelerometer data were included to investigate the association of CRAR with incidental dementia. Non‐parametric CRAR parameters were utilized, including activity level during active periods of the day (M10), activity level during rest periods of the day (L5), and the relative difference between the M10 and L5 (relative amplitude, RA). Associations of CRAR with cognitive dysfunction and brain structure were studied in a subset of participants. Neuroimaging‐transcriptomics analysis was utilized to identify the underlying molecular mechanisms. Results Over 6.86 (4.94–8.78) years of follow‐up, 494 participants developed dementia. The risk of incident dementia was associated with decreasing M10 (hazard ratio [HR] 1.45; 95% conference interval [CI], 1.28–1.64) and RA (HR 1.37; 95% CI, 1.28–1.64), increasing L5 (HR 1.14, 95% CI 1.07–1.21) and advanced L5 onset time (HR 1.12; 95% CI, 1.02–1.23). The detrimental associations were exacerbated by APOE ε4 status and age (>65 years). Decreased RA was associated with lower processing speed (Beta −0.04; SE 0.011), predominantly mediated by abnormalities in subcortical regions and white matter microstructure. The genes underlying CRAR‐related brain regional structure variation were enriched for synaptic function. Conclusions Our study underscores the potential of intervention targeting at maintaining a healthy CRAR pattern to prevent dementia risk.