CHRONO:MEDICINE

• E28 - The Central Clock & Melatonin with Michael Hastings (EBRS 2025 Spotlight 1)

  In collaboration with the organizers of the 18th Congress of the European Biological Rhythms Society (EBRS) (taking place in Lübeck in Northern Germany from the 24th to 28th of August 2025), three congress speakers are interviewed to talk about their research. As the first spotlight, Prof. Michael Hastings (MRC Laboratory of Molecular Biology, Cambridge) talks about his research journey from circatidal rhythms in marine organisms to circadian and circaannual rhythms in mammals. Our main focus is on the neurochemistry within the central clock of the suprachiasmatic nucleus (SCN) enabling it to tell time. We discuss the most relevant factors that support the SCN in telling time, and what means the SCN has to synchronize other clocks within our body. With respect to melatonin, we discuss its role in sleep versus informing our body about the current season. We also talk about supplementing melatonin for specific populations. Lastly, Michael shares memories from attending previous EBRS congresses and why you should consider joining it this year.Chapters:(00:00:39) Introducing the EBRS 2025 spotlights(00:03:51) Michael Hastings(00:07:17) Circatidal rhythms(00:14:38) The central clock or SCN(00:24:47) Different zeitgebers(00:35:17) Melatonin(00:46:14) Melatonin as a sleeping aid(00:51:38) EBRS congress experience(00:58:22) Career advice(01:10:02) Funny anecdote(01:13:54) Outro Studies that Michael refers to:Reviews on circatidal rhythmshttps://doi.org/10.1016/j.cub.2008.06.041https://doi.org/10.1016/j.tig.2024.01.006 Prevalence of mutations in clock genes to make the period length shorter or longer than approx. 24 hours, rare familial sleep disordershttps://doi.org/10.1038/s41386-019-0476-7 Mice mutations support that the same enzymes are involved as in the human sleep disordershttps://www.nature.com/articles/s41583-018-0026-z Period genes in the SCN are activated by lighthttps://doi.org/10.1016/S0092-8674(00)80494-8 Caffeine can phase shift the circadian clockhttps://doi.org/10.1126/scitranslmed.aac5125 Manipulation of NPY and serotonin can shift the SCN clock https://doi.org/10.1152/ajpregu.00320.2022 Human cortisol levels increase before awakening in anticipation of wakehttps://doi.org/10.1677/JOE-07-0378 Temperature in the physiological range can act as a zeitgeber to entrain peripheral clockshttps://doi.org/10.1016/S0960-9822(02)01145-4 When interfering with neuropeptide levels within the SCN, you can entrain the SCN with temperature cycleshttps://doi.org/10.1126/science.1195262 High levels of estradiol make the SCN run fasterhttps://doi.org/10.1126/science.557840 Melatonin is a transplacental zeitgeberhttps://pubmed.ncbi.nlm.nih.gov/3780553/https://doi.org/10.1177/074873049701200603 Martha Gillette and others applied melatonin to brain slides containing the SCN, showing that this could shift the SCN clock, the sensitivity of the SCN to this melatonin effect was found to occur during daytime (when melatonin is not released naturally)https://link.springer.com/article/10.1007/s00441-002-0576-1 GWAS papers: variance of melatonin receptor are related to the type 2 diabetes andmetabolic disordershttps://www.nature.com/articles/ng.277https://www.nature.com/articles/s41574-018-0130-1Contacting Michael Hastings:Homepage: https://www2.mrc-lmb.cam.ac.uk/group-leaders/h-to-m/michael-hastings/Email: ⁠[email protected]⁠EBRS homepage:https://ebrs-online.org

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• E27 - Part 2: A good night's sleep with Christian Benedict

  In this second part, Dr. Christian Benedict (Department of Pharmaceutical Biosciences, Research and Pharmacology at Uppsala University, Sweden) explains how our sleep changes with aging and upon different challenges of adult life. We discuss the so-called gold-standard method for measuring sleep (Polysomnography, PSG) and how modern wearable technologies perform compared to PSG. In this context, Christian evaluates the potential value of measuring heart rate variability (HRV) to assess sleep quality. He also emphasizes the health threat through obstructive sleep apnea (OSA) and how to use simple self-monitoring technologies to determine if you may be affected by OSA yourself. Lastly, we acknowledge poor sleep as a general health risk but also discuss limitations and problems that can arise from overstating this. Chapters:(0:00:12) Intro(0:02:20) Aging and sleep(0:11:10) Polysomnography (PSG)(0:22:25) Sleep wearables & HRV(0:27:07) Obstructive sleep apnea(0:33:10) Limitations of wearables(0:36:41) Sleep across chronotypes(0:44:50) Poor sleep as a health risk?(0:55:19) Outro Studies that Christian refers to:Meta-analysis (2004) PSG data over the lifespanhttps://pubmed.ncbi.nlm.nih.gov/15586779/ Paper on app findings of almost a million people asked on “how long do you sleep?”https://pubmed.ncbi.nlm.nih.gov/36509747/ Studies on PSG vs. some commercial wearables ?https://jcsm.aasm.org/doi/10.5664/jcsm.7128 Sleep apnea: Spotlight article with Jesse Cooks and Jonathan Cedernaeshttps://pubmed.ncbi.nlm.nih.gov/33180697/ Lancet Respiratory Medicine review, 425 million people suffer from moderate to severeobstructive sleep apneahttps://pubmed.ncbi.nlm.nih.gov/31300334/ Ad-hoc sleep apnea screening in patients admitted to the hospital, 80% are not aware of ithttps://pubmed.ncbi.nlm.nih.gov/19186102/ Australian study using a measurement pillow to track sleep apneahttps://www.atsjournals.org/doi/full/10.1164/rccm.202107-1761OC Christian’s work (2015) those who have over 40 years regular sleep problems have an increased risk for Alzheimer’shttps://pubmed.ncbi.nlm.nih.gov/25438949/ Studies comparing people with kids and without kids, those with kids live longerhttps://jech.bmj.com/content/71/5/424  How to contact Christian Benedict:Email: [email protected]: https://www.linkedin.com/in/christian-benedict-a25b1615a/

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• E26 - Part 1: A good night's sleep with Christian Benedict

  Dr. Christian Benedict (Senior Lecturer & Associate Professor at the Department of Pharmaceutical Biosciences, Research and Pharmacology at Uppsala University, Sweden) talks about how to study sleep and its relevance for our overall health. In this first part, Christian introduces us to different definitions of sleep. Together, we try to decipher the concept of sleep quality or in other words how to judge if somebody had a good night’s sleep or not. Christian also summarizes the research around the optimal duration of sleep and discusses the relevanceof spending time in different sleep stages.Chapters:(0:00:12) Intro(0:03:41) Christian Benedict’s career path(0:13:06) What is sleep?(0:24:09) Sleep stages & sleep quality (0:34:06) Sleep quantity/duration(0:42:08) Outro & Teaser to Part 2 Studies that Christian refers to:Aversive tobacco smoke during non-REM sleephttps://pubmed.ncbi.nlm.nih.gov/25392505/Epileptic patients and sleep deprivationhttps://pubmed.ncbi.nlm.nih.gov/29106402/Correlations between time in different sleep stages and daytime alertness are not that good, contradictory evidencehttps://pubmed.ncbi.nlm.nih.gov/10678518/Epworthsleepiness scale and sleep stages are not well correlatedhttps://pubmed.ncbi.nlm.nih.gov/19110886/ People struggling with sleep do not necessarily differ in PSG-derived sleep stage outcomes from normally sleeping peoplehttps://pubmed.ncbi.nlm.nih.gov/29402512/ Peer feedback can impact your retrospective judgement of your last night of sleephttps://pubmed.ncbi.nlm.nih.gov/24417326/https://pubmed.ncbi.nlm.nih.gov/33204201/American Society for Sleep Medicine, 7-9 hours, probably 6 and 10 hours are also finehttps://www.thensf.org/wp-content/uploads/2020/10/NSF-SleepDurationTiming_Background-1200x1312-1.jpg Shorter or longer than these 6-10 hours is mostly associated with poor health outcomeshttps://pubmed.ncbi.nlm.nih.gov/11825133/ Christian’s work on interindividual responses in brain health outcomes to sleep losshttps://pubmed.ncbi.nlm.nih.gov/36088460/ Studies showing that people who think they cope well with sleep loss are actually not doing wellhttps://pubmed.ncbi.nlm.nih.gov/29383809/ How to contact Christian Benedict:Email: [email protected]: https://www.linkedin.com/in/christian-benedict-a25b1615a/

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• E25 - Part 2: Improving health & sleep through daylight with Christian Cajochen

  In the second part with Prof. Christian Cajochen (Head of the Centre for Chronobiology at the University of Basel in Switzerland), contributing to the Daylight Awareness Week (28th of October - 2nd of November 2024), we continue our discussion around the impact of daylight on our health, with a special focus on sleep. Christian summarizes the negative effects of bright electric light exposure on sleep and other health outcomes. On the other hand, he highlights the importance of daylight and alternatively increased electric light intensities during daytime for sleep. We also discuss how seasonal changes in daylight affect us more than we think. Christian gives insights into a real-world example of how switching to dynamic lighting at the workplace changed people’s wellbeing. And lastly, we discuss if a medical pill could eventually replace the health effects of daylight. More information about the Daylight Awareness Week: ⁠https://daylight.academy/daylight-awareness-week-2024/⁠ Chapters: (0:00:12) Intro & Daylight Awareness Week (0:00:48) Topics of this episode series (0:02:13) Introduction to sleep (0:04:15) Evening electric light & sleep (0:09:42) Daylight & sleep (0:15:47) Seasonal effects of daylight (0:20:33) Can higher light intensities during daytime reduce negative effects of evening light? (0:25:47) How to tackle the lack of daylight as a society? (0:36:00) Take-home message on daylight & health (0:37:39) Christian’s career goals & future research (0:41:15) Funny anecdotes (0:47:18) Outro & Teaser to Part 2 Studies that Christian refers to: Evening administration of melatonin and bright light: Interactions on the EEG during sleep and wakefulness https://doi.org/10.1046/j.1365-2869.1998.00106.x Blue Blocker Glasses as a Countermeasure for Alerting Effects of Evening Light-Emitting Diode Screen Exposure in Male Teenagers https://doi.org/10.1016/j.jadohealth.2014.08.002 Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study) https://doi.org/10.1289/EHP1837 Camping Study: “Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend” 10.1016/j.cub.2016.12.041 Effect of daylight LED on visual comfort, melatonin, mood, waking performance and sleep https://doi.org/10.1177/1477153519828419 Positive Effect of Daylight Exposure on Nocturnal Urinary Melatonin Excretion in the Elderly: A Cross-Sectional Analysis of the HEIJO-KYO Study https://doi.org/10.1210/jc.2012-1873 Effect of Bright Light and Melatonin on Cognitive and Noncognitive Function in Elderly Residents of Group Care Facilities: A Randomized Controlled Trial https://doi.org/10.1001/jama.299.22.2642 Preprint article: “Sex and seasonal variations in melatonin suppression, and alerting response to light” https://doi.org/10.1101/2024.10.18.619012 Light therapy in non-seasonal depression: An update meta-analysis https://doi.org/10.1016/j.psychres.2020.113247 Pre-print article: “Afternoon to early evening bright light exposure reduces later melatonin production in adolescents” https://doi.org/10.1101/2024.10.02.616112 Regular Caffeine Intake Delays REM Sleep Promotion and Attenuates Sleep Quality in Healthy Men https://doi.org/10.1177/07487304211013995 Evidence that the Lunar Cycle Influences Human Sleep 10.1016/j.cub.2013.06.029 How to contact Christian Cajochen: Email: [email protected] Twitter: @ollen44 LinkeIn: https://www.linkedin.com/in/christian-cajochen-1435258/

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• E24 - Part 1: Improving health & sleep through daylight with Christian Cajochen

  As part of the Daylight Awareness Week (28th of October - 2nd of November 2024), Prof. Christian Cajochen (Head of the Centre for Chronobiology at the University of Basel in Switzerland) talks about the impact of daylight on our health, with a special focus on sleep. In the first part, we talk about the importance of light for the circadian timing system within our bodies, with melatonin playing an important role. Christian explains why light can have very different effects on our health depending on the time of day of light exposure, and highlights the most important time to see daylight. Christian points out the benefits of daylight particularly for older people. We also critically discuss how difficult it is to study the health effects of daylight without any confounding from other "side-benefits" outdoors. And lastly, we discuss the effects of light on our cardiovascular system (like heart rate and blood pressure) as well as alertness. More information about the Daylight Awareness Week: https://daylight.academy/daylight-awareness-week-2024/ Chapters: (0:00:12) Intro & Daylight Awareness Week (0:02:10) Topics of this episode series (0:03:33) Introducing Christian Cajochen (0:08:21) Daylight vs. electric light (0:13:28) Circadian clocks & melatonin (0:20:31) Wavelength dependency (0:23:13) Timing of light matters (0:30:43) How to study health effects of daylight without confounders? (0:38:32) Light & Cardiovascular health (0:45:31) Warm feet to promote sleep (0:52:14) Light & Blood pressure (0:56:11) Outro & Teaser to Part 2 Studies that Christian refers to: The aging clock: circadian rhythms and later life https://doi.org/10.1172/JCI90328 A Phase Response Curve to Single Bright Light Pulses in Human Subjects https://doi.org/10.1113/jphysiol.2003.040477 Positive Effect of Daylight Exposure on Nocturnal Urinary Melatonin Excretion in the Elderly: A Cross-Sectional Analysis of the HEIJO-KYO Study https://doi.org/10.1210/jc.2012-1873 The biological clock tunes the organs of the body: timing by hormones and the autonomic nervous system https://doi.org/10.1677/joe.0.1770017 Light activates the adrenal gland: Timing of gene expression and glucocorticoid release 10.1016/j.cmet.2005.09.009 Warm feet promote the rapid onset of sleep https://www.nature.com/articles/43366 Functional link between distal vasodilation and sleep-onset latency? https://doi.org/10.1152/ajpregu.2000.278.3.R741 Changing color and intensity of LED lighting across the day impacts on circadian melatonin rhythms and sleep in healthy men https://doi.org/10.1111/jpi.12714 Circadian mechanisms of 24-hour blood pressure regulation and patterning https://doi.org/10.1016/j.smrv.2016.02.003 Alerting effects of light https://doi.org/10.1016/j.smrv.2007.07.009 How to contact Christian Cajochen: Email: [email protected] Twitter: @ollen44 LinkeIn: https://www.linkedin.com/in/christian-cajochen-1435258/

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