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. Author manuscript; available in PMC: 2010 Jun 1.
Published in final edited form as: Sleep Med Clin. 2009 Jun 1;4(2):285–299. doi: 10.1016/j.jsmc.2009.02.003

Figure 1.

Figure 1

Schematic diagram of normal phase relationships (rounded to the nearest integer) between sleep phase markers, the 10 pg/ml plasma dim light melatonin onset (DLMO) derived from historical controls. The present study used the melatonin/mid-sleep interval (phase angle difference, or PAD) of 6 hours as the hypothesized therapeutic window for optimal circadian alignment. Sleep times were determined actigraphically. Plasma melatonin levels were obtained under dim light every 30 minutes in the evening. The operational definition of the melatonin onset is the interpolated time of continuous rise above the threshold of 10 pg/ml; for example, if the melatonin level at 8 p.m. was 5 pg/ml and at 8:30 p.m. was 15 pg /ml, the melatonin onset would be 8:15 p.m. Adapted from[7], with permission.