Circadian sleep, illumination, and activity patterns in women: influences of aging and time reference

Patterns of sleep, illumination, and activity of women of different ages we re continuously monitored in their natural environments with a wrist activi ty monitor. Partial correlation analyses were performed to determine relati onships between age and sleep and several circadian rhythm measures includi ng the amplitudes, mesors, and timings of sleep, of illumination, and of ac tivity. We found no age-related decline in actigraphic sleep duration. Age was not a significant correlate of circadian rhythm parameters of sleep. Mo reover, no age effects were found on daily illumination exposure or on the circadian timing of illumination and activity patterns. However, the level and amplitude of the circadian activity rhythm showed a gradual decline wit h aging, independent of the time reference (i.e., Daylight Saving Time vers us Standard Time) when recordings were obtained. As expected, significant a ssociations were observed between local time reference and the level and ti ming of peak of illumination patterns. However, changes in local time refer ence were not significantly and consistently associated with actigraphic sl eep or activity measures. (C) 2000 Elsevier Science Inc. All rights reserve d.