Heart Rate Variability Time-Domain Analysis Across Glaucoma Subtypes

<b>Background/Objectives</b>: The association between glaucoma and autonomic nervous system (ANS) function remains unclear. Primary open-angle glaucoma (POAG) and exfoliation glaucoma (EXG) have distinct pathophysiological mechanisms, which may lead to different ANS alteration. This study aimed to investigate the association between different glaucoma subtypes and the following time-domain heart rate variability (HRV) parameters: the standard deviation of normal-to-normal intervals (SDNN), the square root of the mean of the sum of the squared differences between adjacent normal-to-normal intervals (RMSSD), and the coefficient of variation of R-R intervals (CVRR). <b>Methods</b>: A total of 809 eyes from 809 patients with POAG, EXG, and controls were included. HRV was measured from the participants' fingertips using a sphygmograph (TAS9 Pulse Analyzer Plus View; YKC Corp., Tokyo, Japan). Comparisons of time-domain HRV parameters among the groups were conducted. To evaluate the associations between time-domain HRV parameters and other variables, linear regression analyses were conducted. <b>Results</b>: This study included 522 participants with POAG, 191 participants with EXG, and 96 participants in the control group. There was a significant difference in CVRR among the groups (the control group: 4.04 ± 2.08%, the POAG group: 3.86 ± 1.87%, the EXG group: 3.57 ± 2.02%; <i>p</i> = 0.010), whereas no significant differences were found in SDNN and RMSSD. The EXG group had significantly lower values of SDNN and CVRR values compared to the POAG group (<i>p</i> = 0.0156 and <i>p</i> = 0.0037, respectively). In multivariate linear regression analysis, the highest recorded intraocular pressure (IOP) was significantly associated with CVRR. <b>Conclusions</b>: HRV parameters may reflect ANS alterations in glaucoma subtypes.