The relationship between apathy and nonparametric variables of rest activity rhythm in older adults with cerebral small vessel disease

The goal of the current study was to demonstrate if the rest-activity rhythm (RAR) was altered in apathetic older adults with cerebral small vessel disease (CSVD) and find out the relationship between apathy/depression severity and RAR features in CSVD patients. This is a cross-sectional observational investigation including 53 CSVD cases (54.74% men), aged 70.70 ± 6.18 years old. The participants were assessed by neuropsychiatric inventory (NPI) subscale of apathy (NPI-apathy) and depression (NPI-depression) in succession, according to updated diagnostic criteria for apathy (DCA). Each subject wore an actigraph device (ActiGraph GT3X) in their nondominant hand for 7 days to collect raw data. Using a non-parametric methodological analysis, this study determined RAR variables such as interdaily stability (IS), intraday variability (IV) and relative amplitude (RA). Patients in the apathy-positive group had a higher Fazekas score than those in the apathy-negative group. IS, but not IV, RA, or objective sleep variables, differed between elderly patients with varying degrees of CSVD burden. Furthermore, apathy severity was statistically correlated with RA after adjusting for age, gender and education level, whereas depression severity was not associated with RAR variables. Finally, we discovered that the severity of apathy had no significant relationship with the severity of depression. All these findings indicated that the RAR altered in apathetic older adults with CSVD, and apathy was associated with decreased RAR amplitude.