S‐cone contribution to the acute melatonin suppression response in humans

Brown, T. M.; Thapan, Kavita; Arendt, Joséphine; Revell, Victoria L.; Skene, Debra J.

doi:10.1111/jpi.12719

Cited by 36 publications

(32 citation statements)

References 48 publications

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“…Additionally, the contribution of other photoreceptors (e.g., S-cones) to the melatonin suppression pattern that we observed needs to be elucidated. 30 Prior studies in adults on the relationship between light intensity and melatonin suppression have employed light exposures lasting several hours and/or anchored to a circadian phase marker. 15,19 In contrast, we utilized an ecologically valid light exposure time (1 h before habitual bedtime) in order to simulate how children are exposed to evening light in their everyday environment.…”

Section: Discussionmentioning

confidence: 99%

High sensitivity of melatonin suppression response to evening light in preschool‐aged children

Hartstein

Behn

Akacem

et al. 2022

Journal of Pineal Research

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Light at night in adults suppresses melatonin in a nonlinear intensity-dependent manner. In children, bright light of a single intensity before bedtime has a robust melatonin suppressing effect. To our knowledge, whether evening light of different intensities is related to melatonin suppression in young children is unknown.Healthy, good-sleeping children (n = 36; 3.0-4.9 years; 39% male) maintained a stable sleep schedule for 7 days followed by a 29.5-h in-home dim-light circadian assessment (~1.5 lux). On the final night of the protocol, children received a 1-h light exposure (randomized to one of 15 light levels, ranging 5-5000 lux, with ≥2 participants assigned to each light level) in the hour before habitual bedtime. Salivary melatonin was measured to calculate the magnitude of melatonin suppression during light exposure compared with baseline levels from the previous evening, as well as the degree of melatonin recovery 50 min after the end of light exposure. Melatonin levels were suppressed between 69.4% and 98.7% (M = 85.4 ± 7.2%) during light exposure across the full range of intensities examined. Overall, we did not observe a light intensity-dependent melatonin suppression response; however, children exposed to the lowest quartile of light intensities (5-40 lux) had an average melatonin suppression (77.5 ± 7.0%) which was significantly lower than that observed at each of the three higher quartiles of light intensities (86.4 ± 5.6%, 89.2 ± 6.3%, and 87.1 ± 5.0%, respectively). We further found that melatonin levels remained below 50% baseline for at least 50 min after the end of light exposure for the majority (62%) of participants, and recovery was not influenced by light intensity. These findings indicate that preschool-aged children are highly sensitive to light exposure in the hour before bedtime and suggest the lighting environment may play a crucial role in the development and the maintenance of behavioral sleep problems through impacts on the circadian timing system.

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Section: Discussionmentioning

confidence: 99%

High sensitivity of melatonin suppression response to evening light in preschool‐aged children

Hartstein

Behn

Akacem

et al. 2022

Journal of Pineal Research

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“…Thus, our results on the PIPR do not contradict published literature but rather suggest a stronger influence of shorter wavelengths than previously thought, below the ipRGC peak at around 490 nm. A possible mechanism might be an S-cone influence on the pupil [ 64 , 65 ], which has been shown to influence other ipRGC-dependent effects, such as circadian alignment in mice [ 66 ] or, very recently, acute Melatonin-suppression in humans [ 67 ]. Circumstances for these additional influences include low light levels and comparatively short stimulus times (less than half an hour), which would fit our setup.…”

Section: Discussionmentioning

confidence: 99%

Spectral dependency of the human pupillary light reflex. Influences of pre-adaptation and chronotype

2022

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Non-visual photoreceptors (ipRGCs) and rods both exert a strong influence on the human pupil, yet pupil models regularly use cone-derived sensitivity as their basis. This inconsistency is further exacerbated by the fact that circadian effects can modulate the wavelength sensitivity. We assessed the pupillary reaction to narrowband light stimuli in the mesopic range. Pupil size for eighty-three healthy participants with normal color vision was measured in nine experimental protocols with varying series of continuous or discontinuous light stimuli under Ganzfeld conditions, presented after 90 seconds of dark adaptation. One hundred and fifty series of stimulation were conducted across three experiments, and were analyzed for wavelength-dependency on the normalized pupillary constriction (nPC), conditional on experimental settings and individual traits. Traits were surveyed by questionnaire; color vision was tested by Ishihara plates or the Lanthony D15 test. Data were analyzed with generalized additive mixed models (GAMM). The normalized pupillary constriction response is consistent with L+M-cone derived sensitivity when the series of light stimuli is continuous, i.e., is not interrupted by periods of darkness, but not otherwise. The results also show that a mesopic illuminance weighing led to an overall best prediction of pupillary constriction compared to other types of illuminance measures. IpRGC influence on nPC is not readily apparent from the results. When we explored the interaction of chronotype and time of day on the wavelength dependency, differences consistent with ipRGC influence became apparent. The models indicate that subjects of differing chronotype show a heightened or lowered sensitivity to short wavelengths, depending on their time of preference. IpRGC influence is also seen in the post-illumination pupil reflex if the prior light-stimulus duration is one second. However, shorter wavelengths than expected become more important if the light-stimulus duration is fifteen or thirty seconds. The influence of sex on nPC was present, but showed no interaction with wavelength. Our results help to define the conditions, under which the different wavelength sensitivities in the literature hold up for narrowband light settings. The chronotype effect might signify a mechanism for strengthening the individual´s chronotype. It could also be the result of the participant’s prior exposure to light (light history). Our explorative findings for this effect demand replication in a controlled study.

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“…There is indirect evidence for rod and cone participation in non-visual responses, 60–62 which may be time-dependent. 63 , 64 Participants with colour vision deficiencies affecting the L (protanopia) or M (deuteranopia) cones show normal melatonin suppression responses to light, indicating that neither class is necessary for melatonin suppression. 65 In animal models, rods have been found to contribute to phase shifting responses, 66 thereby effectively extending the range at which light can contribute to circadian photoentrainment.…”

Section: Discussionmentioning

confidence: 99%

Sleep and circadian phenotype in people without cone-mediated vision: a case series of fiveCNGB3and twoCNGA3patients

Spitschan

Garbazza

Kohl

et al. 2021

Brain Communications

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Light exposure entrains the circadian clock through the intrinsically photosensitive retinal ganglion cells, which sense light in addition to the cone and rod photoreceptors. In congenital achromatopsia (prevalence 1:30–50,000), the cone system is non-functional, resulting in severe light avoidance and photophobia at daytime light levels. How this condition affects circadian and neuroendocrine responses to light is not known. In this case series of genetically confirmed congenital achromatopsia patients (n = 7; age 30–72 years; 6 women, 1 male), we examined survey-assessed sleep/circadian phenotype, self-reported visual function, sensitivity to light and use of spectral filters that modify chronic light exposure. In all but one patient, we measured rest-activity cycles using actigraphy over 3 weeks and measured the melatonin phase angle of entrainment using the dim-light melatonin onset. Due to their light sensitivity congenital achromatopsia patients used filters to reduce retinal illumination. Thus, congenital achromatopsia patients experienced severely attenuated light exposure. In aggregate, we found a tendency to a late chronotype. We found regular rest-activity patterns in all patients and normal phase angles of entrainment in participants with a measurable dim-light melatonin onset. Our results reveal that a functional cone system and exposure to daytime light intensities are not necessary for regular behavioural and hormonal entrainment, even when survey-assessed sleep and circadian phenotype indicated a tendency for a late chronotype and sleep problems in our congenital achromatopsia cohort.

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S‐cone contribution to the acute melatonin suppression response in humans

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 36 publications

References 48 publications

High sensitivity of melatonin suppression response to evening light in preschool‐aged children

High sensitivity of melatonin suppression response to evening light in preschool‐aged children

Spectral dependency of the human pupillary light reflex. Influences of pre-adaptation and chronotype

Sleep and circadian phenotype in people without cone-mediated vision: a case series of fiveCNGB3and twoCNGA3patients

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