These actigraphic recordings are from a nurse who works the day shift and a nurse who works the night shift. A 24-hour time interval (ranging from 12:00 PM to 12:00 PM) is depicted on the X-axis; sequential dates are depicted on the Y-axis. Note that typical sleep periods (eg, 10:00 PM to 6:00 AM) are in the center of the actigram. The actigram denotes physical activity in black, which correlates with wakefulness. An absence of physical activity correlates with pronounced inactivity and periods of sleep. Periods of sleep (aqua) are determined by the actigraphy software. This actigram also provides light exposure by wavelength, including white, red, green, and blue. In this figure, the day shift nurse appears to go to bed between 11:00 PM and 12:30 AM each night and gets out of bed between 6:00 AM and 7:00 AM each day with the exception of day 3 (Saturday), when they appear to stay in bed until 9:00 AM. In contrast, the night shift nurse has variable sleep-wake periods that correspond to their work schedule. For example, the night shift nurse appears to go to bed between 11:00 PM and 3:00 AM on days 2 to 4 and between 8:00 AM and 8:30 AM on days 5 to 7.
