Sleep onset and cardiovascular activity in primary insomnia.
Level 4 - case-series / case-control
Case-control comparative physiological study
PubMed 20673289 · doi:10.1111/j.1365-2869.2010.00871.x
What was done
Researchers evaluated cardiovascular and autonomic activity before and after sleep onset in 8 participants with primary insomnia (DSM-IV criteria) and 8 normal sleepers. Non-invasive measures including heart rate, stroke volume, cardiac output, and pre-ejection period were recorded using impedance cardiography alongside overnight polysomnography. Frequency domain measures of heart rate variability (low-frequency and high-frequency power) were also assessed.
What was found
No exact numerical values were reported in the abstract. Both groups showed decreases in heart rate and cardiac output alongside increases in stroke volume and normalized high-frequency power after falling asleep. However, pre-ejection period increased after sleep onset in normal sleepers but remained unchanged in individuals with insomnia. Pre-ejection period was also significantly lower in insomniacs compared to normal sleepers during both wakefulness and sleep.
Why it matters
This study provides objective physiological evidence that individuals with primary insomnia fail to show normal sympathetic deactivation during the transition to sleep, supporting the physiological hyperarousal model of insomnia.
Limits
The study had an extremely small sample size of 16 participants total (8 per group). The abstract does not provide demographic details such as age or sex, nor does it provide quantitative values, effect sizes, or confidence intervals. Potential first-night effects during laboratory polysomnography were not addressed in the abstract.
Cited by
- contradicts A resting heart rate of 60 beats per minute or below is required to fall into sleep and enter unconsciousness.