Seasonal covariation of the circadian phases of rectal temperature and slow wave sleep onset

Abstract

SUMMARYThere is a scarcity of well-controlled studies of the seasonal variation in circadian rhythmicity. In the present study, the circadian phase of rectal temperature and the onset of slow wave sleep were studied in a series of twelve 24-h experiments, one each month of the year, for six healthy subjects under controlled conditions in a climatic chamber. In winter, as compared with summer, the average circadian rhythm of rectal temperature was phase delayed by 45 min, and the average onset of slow wave sleep was phase delayed by 40 min. The temporal relationship between the circadian phase of rectal temperature and the timing of slow wave sleep was maintained throughout the year. Habitual rising and retiring times covaried as well. Furthermore, the circadian rhythm of rectal temperature followed the timing of the photoperiod across the year, but had a much smaller range of seasonal variation. Apparently, the seasonal variation in the photoperiodic zeitgeber is largely compensated for by the stabilizing influence of secondary zeitgebers. However, in healthy subjects some effect of photoperiodic variation can still be observed.

24-Hour Assessment of Performance on a Palmtop Computer: Validating a Self-Constructed Test Battery

“…Results on the training tests showed minor learning effects on the response latencies of the memory and the choice reaction time test (CRT), whereas percentages correct of the three tests showed no learning effects. During the entire course of the 24 h constant routine protocol (Dongen et al, 1997) the participants had to stay awake while in bed in supine position. Subjects were not allowed to drink coffee, tea, or alcoholic beverages for at least 12 h preceding the start of the experiment.…”

Seasonal changes in human sleep–wake rhythm in Antarctica and Japan

“…Then sleep is regarded as 1, and awake as 0. For consecutive 10‐day 0–1 data, the χ 2 periodgram was computed. In this study, Q 24 values (period = 24 h) were used as a parameter to observe the synchronization to a 24‐h period.…”

“…They completed a sleep log for 12 to 18 months, and the sleep–wake state was scored in 10‐min epochs. Q 24 values calculated by χ 2 periodgram were low in the Antarctic midwinter. This means that there was difficulty in synchronizing to a 24‐h period in the Antarctic midwinter.…”

Ritmos biológicos em índios Guarani adultos

“…Alguns pesquisadores afirmam não haver alteração na expressão de variáveis biológicas durante o ano (Laakso et al, 1994;Van Dongen et al, 1998;Wehr et al, 1995) enquanto que outros observam um atraso na expressão dos ritmos no inverno (Honma et al, 1992;Van Dongen et al, 1997) Estes resultados contraditórios com relação à variação sazonal dos ritmos biológicos humanos geralmente são atribuídos ao nosso estilo de vida contemporâneo e aos padrões temporais de exposição à luz artificial (Bronson, 2004;Wehr et al, 1993). Estudar comunidades indígenas que moram em locais sem energia elétrica permitiria verificarmos diferenças sazonais em ritmos biológicos que apresentam diferente plasticidade.…”

“…Para os índios o avanço nos horários de repouso durante o inverno não condizem com estudos no qual pesquisadores observaram um atraso do sono e de outros ritmos (melatonina, temperatura e cortisol) na mesma época (Bekinschtein et al, 2004;Binkley et al, 1990;Honma et al, 1992;Van Dongen et al, 1997) ou até mesmo com nenhum efeito sazonal sobre os ritmos biológicos (Laakso et al, 1994;Van Dongen et al, 1998;Wehr et al, 1995).…”