I think the timing the student suggests may be about right, but the reasoning wrong. In general I believe you'd see the most profound slowing of HR early in the sleep cycle during non-REM sleep, not at 4 AM when the individual is more likely to be in REM. REM is associated with more variability in HR and BP, sometimes extreme (possible heart attacks?). There are also some cardiac arrhythmias that specifically occur during REM (e.g. REM sleep Sinus Arrest). And, being an asthmatic, I know that ~4 am is among the most common times for severe asthma attacks because that's around the low point in the cortisol cycle. Sleep apnea could also be a risk factor but I don't think apnea peaks at 4AM.
Linda Walsh University of Northern Iowa [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
