Regional Gray Matter Volume Links Rest-Activity Rhythm Fragmentation With Past Cognitive Decline

Objectives We examined the extent to which measures of neurodegeneration and cerebrovascular disease explain the rest-activity rhythm (RAR)-cognition link. Methods Seventy participants (mean age at MRI = 86, standard deviation (SD) = 2.6; 53% female) had cognitive, MRI, and accelerometer data. The slope of cognitive decline was defined applying a mixed model to 10 repeated Modified Mini Mental Status Test (3MS) measures over 14 years. Regional gray matter volume (GMV), white matter hyperintensities, and RARs were measured around year 12. Results Past 3MS decline was related to RAR fragmentation (per SD β = −0.43, 95% confidence interval: −0.73, −0.14) and lower posterior parietal GMV (per standard deviation β = 0.47, 95% confidence interval: 0.14, 0.79). Higher RAR fragmentation was related to lower posterior parietal GMV (Pearson r = −0.39, n = 70, p = 0.0007), which attenuated the association of RAR fragmentation and past cognitive decline by 17%. Conclusions Longitudinal studies are warranted to understand the temporal relations and mechanisms linking RAR fragmentation and neurodegeneration.