Past Issues

Objectives: Sleep affects the regulation of circulatory and respiratory function.
The factors of age and gender are also known to have a signifi cant impact on
the cardiac physiology. We investigated the impact of the factors of age and gender
on sleep-related cardiovascular and respiratory dynamics with a novel, validated
cardiopulmonary coupling analysis based solely on the electrocardiogram (ECG)
signal. Methods: We recruited 155 healthy subjects (41 males and 114 females,
aged 37.6 ± 13.0 years, range being 19-67 years) to participate in this study. We
evaluated their mood and sleep with self-reported questionnaires - the Beck Depression
Inventory, the Pittsburgh Sleep Quality Index, and the Epworth Sleepiness
Scales. Physiologic sleep measures were quantifi ed by analysis of continuous
ECG recordings using the cardiopulmonary coupling analysis. Three sleep states
were determined, namely stable, unstable, and rapid eye movement (REM)/wake
state, by measuring the degree of association between autonomic and respiratory
drives during sleep. Results: The key fi ndings in this study included: (A) Compared
to subjects under age 40, subjects over age 40 showed to have signifi cantly
decreased very-low-frequency coupling, an index of REM/wake state. (B) Compared
to female subjects, male subjects revealed to have lower high-frequencycoupling,
an index of stable sleep, and higher low-frequency-coupling, an index of
unstable sleep. And (C) ECG-based sleep characteristics were not fount to be correlated
with self-reported questionnaires in this healthy adult sample. Conclusions:
Our study results showed that aging and gender as factors had signifi cant
effects on cardiopulmonary coupling dynamics during sleep. This study also provided
a profi le of the physiological sleep characteristics of a healthy Taiwanese
sample. We suggest that further research may enhance the use of this relatively
simple ECG-based method to give a cost-effi cient way to objectively evaluate
sleep quality.