Submitted on November 7, 2005
Accepted on April 29, 2006
The link between cardiac autonomic activity and sleep delta power is altered in men with sleep apnea-hypopnea syndrome
Fabrice Jurysta1*, Jean-Pol Lanquart1, Philippe van de Borne2, Pierre-Francois Migeotte3, Martine Dumont4, Jean-Paul Degaute2, and Paul Linkowski1
1 Sleep Laboratory, Department of Psychiatry, Erasmus Academic Hospital of Free University of Brussels, Brussels, Belgium
2 Department of Cardiology and Hypertension Clinic, Erasmus Academic Hospital of Free University of Brussels, Brussels, Belgium
3 Biomedical Physics Laboratory, Free University of Brussels, Brussels, Belgium
4 Experimental Physics Laboratory, University of Mons-Hainaut, Mons, Belgium
* To whom correspondence should be addressed. E-mail: fajuryst{at}ulb.ac.be.
Aim of the study
We hypothesize that sleep apnea-hypopnea alter interaction between cardiac vagal
modulation and sleep delta EEG.'
Background
Sleep apnea-hypopnea syndrome (SAHS) is related to cardiovascular complications in men. SAHS patients show higher sympathetic activity than normal subjects. In healthy men, NREM sleep is associated with cardiac vagal influence while REM sleep is linked to cardiac sympathetic activity. Interaction between cardiac autonomic modulation and delta sleep EEG is not altered across a life span nor is the delay between appearances of modifications in both signals.
Methods and Results
Healthy controls, moderate SAHS and severe SAHS patients were compared across the first three NREM-REM cycles. Spectral analysis was applied to ECG and EEG signals. High frequency (HF), low frequency (LF) of heart rate variability (HRV), ratio LF/HF, and normalized (nu) delta power were obtained. A coherency analysis between HFnu and delta was performed as well as a correlation analysis between obstructive apnea index (AI) or hypopnea index (HI) and gain, coherence or phase shift. HRV components were similar between groups. In each group, HFnu was larger during NREM while LFnu predominated across REM and wake stages. Coherence and gain between HFnu and delta decreased from controls to severe SAHS patients. In SAHS patients, the delay between modifications in HFnu and delta did not differ from zero. AI and HI correlated negatively with coherence while HI correlated negatively with gain only.
Conclusions
Apneas-hypopneas affect the link between cardiac sympathetic and vagal modulation and delta EEG demonstrated by the loss of cardiac autonomic activity fluctuations across shifts in sleep stages. Obstructive apneas and hypopneas alter the interaction between both signals differently.
