Heart rate variability during the MSLT and MWT in patients with and without excessive daytime sleepiness

Abstract

Autonomic heart regulation changes during the transition from wakefulness to sleep. Heart rate variability (HRV) can be used to assess the autonomic nervous system function (ANS). We aimed to evaluate ANS in patients with and without excessive daytime sleepiness (EDS) during the maintenance of wakefulness test (MWT) and multiple sleep latency test (MSLT). From a series of 98 consecutive patients with symptoms of sleep disordered breathing (SDB) studied with 5 trials of MWT followed by a research version MSLT two groups of patients (matched by age and gender) were selected consecutively based on mean sleep latencies: the sleepy group (SG) with 17 patients ( MWT < 20 min and MSLT < 8 min) and the alert group (AG) with 20 patients (AG: MWT > 20 and MSLT > 8 min). For each test, the first 120-s window of RR signals during wakefulness was analyzed in the following frequency bands: VLF, < 0.04 Hz; LF, 0.04–0.15 Hz; HF, 0.15–0.4 Hz; TB, total-frequency band. ANS activity was described by measures obtained from traditional power spectral analysis (PSA) and from time–frequency representation (TFR). Non-linear measures – Correntropy (CORR) and auto-mutual-information function (AMIF) – were used to describe the RR regularity. Mean values from all day were compared between groups. Cohen’s effect size was calculated to measure the strength of each difference. Finally, a conditional forward logistic regression analysis was performed to find the best discriminatory variables between groups. TFR (in HF and VLF band), AMIF (in all bands) and CORR (in Total band) analysis showed that the SG had higher values than the AG ( p range 0.000–0.02) during the MSLT. The strongest differences were found in HF band from TRF and AMIF and in Total band from AMIF and CORR. The best sensitivity (82.4%) and specificity (85%) to distinguish patients with and without sleepiness were achieved with the combination of AMIF and CORR in Total band, respectively. No differences were found in traditional PSA measures. Heart rate variability analysis during the first 2 min of the MSLT while the patient is awake show specific changes in TFR and non-linear measures that differentiate sleepy from non-sleepy patients. Study supported by FIS PI07/0318 to MS, cofinanced by FEDER.