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Timing of sleep and its relationship with the endogenous melatonin rhythm.

Sletten TL, Vincenzi S, Redman JR, Lockley SW, Rajaratnam SM - Front Neurol (2010)

Bottom Line: We examined the effects of different sleeping schedules on the time of dim light melatonin onset (DLMO) in 28 young, healthy adults.The 2-h difference between groups in the enforced sleep-wake schedule was associated with a concomitant 1.75-h delay in DLMO.The variance in DLMO time, however, was greater in the late group (range 4.5 h) compared to the early group (range 2.4 h) perhaps due to greater effect of environmental influences in delayed sleep types or greater intrinsic instability in their circadian system.

View Article: PubMed Central - PubMed

Affiliation: School of Psychology and Psychiatry, Monash University Clayton, VIC, Australia.

ABSTRACT
While much research has investigated the effects of exogenous melatonin on sleep, less is known about the relationship between the timing of the endogenous melatonin rhythm and the sleep-wake cycle. Significant inter-individual variability in the phase relationship between sleep and melatonin rhythms has been reported although the extent to which the variability reflects intrinsic and/or environmental differences is unknown. We examined the effects of different sleeping schedules on the time of dim light melatonin onset (DLMO) in 28 young, healthy adults. Participants chose to maintain either an early (22:30-06:30 h) or a late (00:30-08:30 h) sleep schedule for at least 3 weeks prior to an overnight laboratory visit. Saliva samples were collected under dim light (<2 lux) and controlled posture conditions to determine salivary DLMO. The 2-h difference between groups in the enforced sleep-wake schedule was associated with a concomitant 1.75-h delay in DLMO. The mean phase relationship between sleep onset and DLMO remained constant (~2 h). The variance in DLMO time, however, was greater in the late group (range 4.5 h) compared to the early group (range 2.4 h) perhaps due to greater effect of environmental influences in delayed sleep types or greater intrinsic instability in their circadian system. The findings contribute to our understanding of individual differences in the human circadian clock and have important implications for the diagnosis and treatment of circadian rhythm sleep disorders, in particular if a greater normative range for phase angle of entrainment occurs in individuals with later sleep-wake schedules.

No MeSH data available.


Related in: MedlinePlus

(A) Individual participants’ melatonin onset (circles) during the first night in the laboratory for the early (n = 11) and late (n = 17) sleep groups. Triangles represent the mean melatonin onset time for each group. Horizontal bars represent the mean sleep period recorded for each group during the final 9 days of the pre-laboratory period. (B) Timing of melatonin onset (circles) relative to scheduled sleep onset (dashed line) (phase angle of entrainment) for each participant in the early (n = 11) and late (n = 17) sleep groups. Triangles represent the mean melatonin onset time for each group.
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Figure 2: (A) Individual participants’ melatonin onset (circles) during the first night in the laboratory for the early (n = 11) and late (n = 17) sleep groups. Triangles represent the mean melatonin onset time for each group. Horizontal bars represent the mean sleep period recorded for each group during the final 9 days of the pre-laboratory period. (B) Timing of melatonin onset (circles) relative to scheduled sleep onset (dashed line) (phase angle of entrainment) for each participant in the early (n = 11) and late (n = 17) sleep groups. Triangles represent the mean melatonin onset time for each group.

Mentions: During the night of the laboratory visit, the time of DLMO for participants in the early group ranged from 19:51 to 22:14 h (21:00 ± 0:41 h; mean ± SD; range 2.4 h). DLMO times for participants in the late group ranged from 20:29 to 01:01 h (22:43 ± 01:21 h; range 4.5 h; Figure 2A). There was a significant difference in DLMO time between the early and late groups, t(24.8) = −4.42, p < 0.001. Levene's test revealed that the variance in DLMO for individuals in the late group was significantly larger than the variance in the early group (F = 5.98, p < 0.05).


Timing of sleep and its relationship with the endogenous melatonin rhythm.

Sletten TL, Vincenzi S, Redman JR, Lockley SW, Rajaratnam SM - Front Neurol (2010)

(A) Individual participants’ melatonin onset (circles) during the first night in the laboratory for the early (n = 11) and late (n = 17) sleep groups. Triangles represent the mean melatonin onset time for each group. Horizontal bars represent the mean sleep period recorded for each group during the final 9 days of the pre-laboratory period. (B) Timing of melatonin onset (circles) relative to scheduled sleep onset (dashed line) (phase angle of entrainment) for each participant in the early (n = 11) and late (n = 17) sleep groups. Triangles represent the mean melatonin onset time for each group.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3008942&req=5

Figure 2: (A) Individual participants’ melatonin onset (circles) during the first night in the laboratory for the early (n = 11) and late (n = 17) sleep groups. Triangles represent the mean melatonin onset time for each group. Horizontal bars represent the mean sleep period recorded for each group during the final 9 days of the pre-laboratory period. (B) Timing of melatonin onset (circles) relative to scheduled sleep onset (dashed line) (phase angle of entrainment) for each participant in the early (n = 11) and late (n = 17) sleep groups. Triangles represent the mean melatonin onset time for each group.
Mentions: During the night of the laboratory visit, the time of DLMO for participants in the early group ranged from 19:51 to 22:14 h (21:00 ± 0:41 h; mean ± SD; range 2.4 h). DLMO times for participants in the late group ranged from 20:29 to 01:01 h (22:43 ± 01:21 h; range 4.5 h; Figure 2A). There was a significant difference in DLMO time between the early and late groups, t(24.8) = −4.42, p < 0.001. Levene's test revealed that the variance in DLMO for individuals in the late group was significantly larger than the variance in the early group (F = 5.98, p < 0.05).

Bottom Line: We examined the effects of different sleeping schedules on the time of dim light melatonin onset (DLMO) in 28 young, healthy adults.The 2-h difference between groups in the enforced sleep-wake schedule was associated with a concomitant 1.75-h delay in DLMO.The variance in DLMO time, however, was greater in the late group (range 4.5 h) compared to the early group (range 2.4 h) perhaps due to greater effect of environmental influences in delayed sleep types or greater intrinsic instability in their circadian system.

View Article: PubMed Central - PubMed

Affiliation: School of Psychology and Psychiatry, Monash University Clayton, VIC, Australia.

ABSTRACT
While much research has investigated the effects of exogenous melatonin on sleep, less is known about the relationship between the timing of the endogenous melatonin rhythm and the sleep-wake cycle. Significant inter-individual variability in the phase relationship between sleep and melatonin rhythms has been reported although the extent to which the variability reflects intrinsic and/or environmental differences is unknown. We examined the effects of different sleeping schedules on the time of dim light melatonin onset (DLMO) in 28 young, healthy adults. Participants chose to maintain either an early (22:30-06:30 h) or a late (00:30-08:30 h) sleep schedule for at least 3 weeks prior to an overnight laboratory visit. Saliva samples were collected under dim light (<2 lux) and controlled posture conditions to determine salivary DLMO. The 2-h difference between groups in the enforced sleep-wake schedule was associated with a concomitant 1.75-h delay in DLMO. The mean phase relationship between sleep onset and DLMO remained constant (~2 h). The variance in DLMO time, however, was greater in the late group (range 4.5 h) compared to the early group (range 2.4 h) perhaps due to greater effect of environmental influences in delayed sleep types or greater intrinsic instability in their circadian system. The findings contribute to our understanding of individual differences in the human circadian clock and have important implications for the diagnosis and treatment of circadian rhythm sleep disorders, in particular if a greater normative range for phase angle of entrainment occurs in individuals with later sleep-wake schedules.

No MeSH data available.


Related in: MedlinePlus