Heart rate variability in epilepsy and its association with disease duration: a retrospective case–control study
Objective To characterize 24-h heart rate variability (HRV) profiles in patients with epilepsy, investigate the association between the standard deviation of normal-to-normal R-R intervals (SDNN) and epilepsy status as well as disease duration, and explore whether hippocampal atrophy and seizure type modify these associations. Methods This single-center retrospective case–control study enrolled 360 participants (180 patients with epilepsy and 180 non-epileptic controls). HRV parameters—including SDNN, RMSSD, pNN50, LF, HF, and LF/HF ratio—were derived from 24-h ambulatory electrocardiographic recordings, with SDNN prespecified as the primary outcome measure. Multivariable linear regression was used to assess the association between epilepsy status and SDNN. Within the epilepsy cohort, partial correlation analysis, multivariable linear regression, linear trend testing, and subgroup interaction analyses were performed to evaluate the association between disease duration and SDNN. Results Compared with controls, the epilepsy group exhibited significantly lower SDNN, RMSSD, LF, and HF values, and a higher LF/HF ratio. Multivariable linear regression revealed that epilepsy status was independently associated with lower SDNN. After adjustment for available confounders, longer disease duration was significantly correlated with lower SDNN (r = −0.573, p < 0.001); each 1-year increase in disease duration was associated with a 1.085 ms decrease in SDNN (95% CI: −1.327 to −0.842, p < 0.001). Linear trend analysis demonstrated a declining SDNN trajectory with increasing disease duration. Subgroup analyses revealed consistent association patterns across subgroups, with no statistically significant interaction effects detected. Conclusion Patients with epilepsy exhibit HRV abnormalities characterized by reduced SDNN, and prolonged disease duration is associated with reduced SDNN. As a simple and non-invasive parameter, SDNN may be useful in reflecting autonomic regulation status in patients with epilepsy and in providing supplementary information for clinical evaluation. However, due to the limitations of the retrospective study design and the composition of the control group, whether the observed HRV abnormalities are specific to epilepsy remains unclear, and further multicenter prospective studies are warranted for validation.