File:Circadian.jpg: Difference between revisions

Circadian graph shows individual sleep preferences that help optimize sleep. The presented graph is based on nearly 12,000 sleep episodes. Light blue dots are sleep episode measurements with the duration of wakefulness on the horizontal axis, and the length of sleep on the left vertical axis. The graph shows the favorite times for falling asleep as counted from the time of natural awakening (blue homeostatic line), as well as the resulting average sleep length produced by various bed time hours (red circadian line). Right vertical axis refers to the percent of sleep episodes initiated at a given hour (blue line). The left verical axis refers to the length of sleep (dots) or the average length of sleep (red line). The blue line is a rough reflection of the homeostatic sleep drive. The red line shows how long sleep lasts depending on the hour at which it was initiated. The red line is a reflection of the circadian sleep component (i.e. the longest sleep occurs at the start of the subjective night). Note that the peak of the sleep length (red) is slightly phase shifted in reference to the sleep drive (blue) due to the fact that long sleep is mostly achieved by initiating sleep too early. The slanting green line separates the graph into the areas of phase advances (right) and phase delays (left). The line is determined by points in the graph where the waking time (horizontal axis) added to the sleep time (left vertical axis) equals to 24.0 hours. The place where the green breakeven line crosses the red sleep length line determines the optimum balanced sleep cycle of 24 hours. The greater the angle between the green and red lines, the harder it is to balance sleep and fit it into the 24h cycle of the rotating earth. In the presented example, the longest sleep occurs after a 17-hour day (peak of the red line), the best adjusted cycle happens after a 19-hour day (crossing of red and green lines), while the usual waking day lasts around 20 hours (peak of the blue line). This example also shows that the optimum siesta time occurs 8 hours after awakening (blue peak). For example, for an awakening at 6 am, the siesta should begin at 2 pm (8h), and the night sleep at 1 am (19h).