by Dr. Jan-Frieder Harmsen
In the CHRONO:MEDICINE podcast (formerly known as 247Muscle), your host (Dr. Jan-Frieder Harmsen) interviews scientists in the field of chronobiology, circadian rhythm, skeletal muscle physiology, exercise performance and sleep. The podcast aims to provide translational knowledge from research findings for students, researchers and the generally interested public.
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12/19/2021
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March 25, 2025
<p>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.</p><p><br></p><p>EBRS homepage: https://ebrs-online.org/index.php/events/ebrs2025.html</p><p><br></p><p>Chapters:</p><p>(0:00:39) Introducing the EBRS 2025 spotlights</p><p>(0:03:51) Michael Hastings</p><p>(0:07:17) Circatidal rhythms</p><p>(0:14:38) The central clock / SCN</p><p>(0:24:47) Different zeitgebers</p><p>(0:35:17) Melatonin</p><p>(0:46:14) Melatonin as a sleeping aid?</p><p>(0:51:38) EBRS congress experience</p><p>(0:58:22) Michael’s career advice</p><p>(1:10:02) Funny anecdote</p><p>(1:13:54) Outro </p><p><br></p><p>Studies that Michael refers to:</p><p>Reviews on circatidal rhythms</p><p><a href="https://doi.org/10.1016/j.cub.2008.06.041" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1016/j.cub.2008.06.041</a></p><p><a href="https://doi.org/10.1016/j.tig.2024.01.006" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1016/j.tig.2024.01.006</a></p><p> </p><p>Prevalence of mutations in clock genes to make the period length shorter or longer than approx. 24 hours, rare familial sleep disorders</p><p><a href="https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.org%2F10.1038%2Fs41386-019-0476-7&data=05%7C02%7C%7C54784fdd86e44f2041ba08dd6b220018%7C5a6d5ee56edf4a26ba93f5872dbb9614%7C0%7C0%7C638784515972133864%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=dsA%2BUeuD1%2Fn2GE8l3TWCuqGrxP8W3spG47cT0qpYBFc%3D&reserved=0" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1038/s41386-019-0476-7</a></p><p> </p><p>Mice mutations support that the same enzymes are involved as in the human sleep disorders</p><p><a href="https://www.nature.com/articles/s41583-018-0026-z" target="_blank" rel="ugc noopener noreferrer">https://www.nature.com/articles/s41583-018-0026-z</a></p><p> </p><p>Period genes in the SCN are activated by light</p><p><a href="https://doi.org/10.1016/S0092-8674(00)80494-8" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1016/S0092-8674(00)80494-8</a></p><p> </p><p>Caffeine can phase shift the circadian clock</p><p><a href="https://doi.org/10.1126/scitranslmed.aac5125" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1126/scitranslmed.aac5125</a></p><p> </p><p>Manipulation of NPY and serotonin can shift the SCN clock </p><p><a href="https://doi.org/10.1152/ajpregu.00320.2022" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1152/ajpregu.00320.2022</a></p><p> </p><p>Human cortisol levels increase before awakening in anticipation of wake</p><p><a href="https://doi.org/10.1677/JOE-07-0378" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1677/JOE-07-0378</a></p><p> </p><p>Temperature in the physiological range can act as a zeitgeber to entrain peripheral clocks</p><p><a href="https://doi.org/10.1016/S0960-9822(02)01145-4" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1016/S0960-9822(02)01145-4</a></p><p> </p><p>When interfering with neuropeptide levels within the SCN, you can entrain the SCN with temperature cycles</p><p><a href="https://doi.org/10.1126/science.1195262" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1126/science.1195262</a></p><p> </p><p>High levels of estradiol make the SCN run faster</p><p><a href="https://doi.org/10.1126/science.557840" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1126/science.557840</a></p><p> </p><p>Melatonin is a transplacental zeitgeber</p><p><a href="https://pubmed.ncbi.nlm.nih.gov/3780553/" target="_blank" rel="ugc noopener noreferrer">https://pubmed.ncbi.nlm.nih.gov/3780553/</a></p><p><a href="https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.org%2F10.1177%2F074873049701200603&data=05%7C02%7C%7C54784fdd86e44f2041ba08dd6b220018%7C5a6d5ee56edf4a26ba93f5872dbb9614%7C0%7C0%7C638784515972488566%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=30bpw2zgmPwC88FnXBHbVHP6ooq1uaUAtfPFofuN44c%3D&reserved=0" target="_blank" rel="ugc noopener noreferrer">https://doi.org/10.1177/074873049701200603</a></p><p> </p><p>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)</p><p><a href="https://link.springer.com/article/10.1007/s00441-002-0576-1" target="_blank" rel="ugc noopener noreferrer">https://link.springer.com/article/10.1007/s00441-002-0576-1</a></p><p> </p><p>GWAS papers: variance of melatonin receptor are related to the type 2 diabetes andmetabolic disorders</p><p><a href="https://www.nature.com/articles/ng.277" target="_blank" rel="ugc noopener noreferrer">https://www.nature.com/articles/ng.277</a></p><p><a href="https://www.nature.com/articles/s41574-018-0130-1" target="_blank" rel="ugc noopener noreferrer">https://www.nature.com/articles/s41574-018-0130-1</a></p><p><br></p><p>Contacting Michael Hastings:</p><p>Homepage: https://www2.mrc-lmb.cam.ac.uk/group-leaders/h-to-m/michael-hastings/</p><p>Email: [email protected]</p>
March 16, 2025
<p>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.</p><p> </p><p>Chapters:</p><p>(0:00:12) Intro</p><p>(0:02:20) Aging and sleep</p><p>(0:11:10) Polysomnography (PSG)</p><p>(0:22:25) Sleep wearables & HRV</p><p>(0:27:07) Obstructive sleep apnea</p><p>(0:33:10) Limitations of wearables</p><p>(0:36:41) Sleep across chronotypes</p><p>(0:44:50) Poor sleep as a health risk?</p><p>(0:55:19) Outro</p><p> </p><p>Studies that Christian refers to:</p><p>Meta-analysis (2004) PSG data over the lifespan</p><p>https://pubmed.ncbi.nlm.nih.gov/15586779/</p><p> </p><p>Paper on app findings of almost a million people asked on “how long do you sleep?”</p><p>https://pubmed.ncbi.nlm.nih.gov/36509747/</p><p> </p><p>Studies on PSG vs. some commercial wearables ?</p><p>https://jcsm.aasm.org/doi/10.5664/jcsm.7128</p><p> </p><p>Sleep apnea: Spotlight article with Jesse Cooks and Jonathan Cedernaes</p><p>https://pubmed.ncbi.nlm.nih.gov/33180697/</p><p> </p><p>Lancet Respiratory Medicine review, 425 million people suffer from moderate to severeobstructive sleep apnea</p><p>https://pubmed.ncbi.nlm.nih.gov/31300334/</p><p> </p><p>Ad-hoc sleep apnea screening in patients admitted to the hospital, 80% are not aware of it</p><p>https://pubmed.ncbi.nlm.nih.gov/19186102/</p><p> </p><p>Australian study using a measurement pillow to track sleep apnea</p><p>https://www.atsjournals.org/doi/full/10.1164/rccm.202107-1761OC</p><p> </p><p>Christian’s work (2015) those who have over 40 years regular sleep problems have an increased risk for Alzheimer’s</p><p>https://pubmed.ncbi.nlm.nih.gov/25438949/</p><p> </p><p>Studies comparing people with kids and without kids, those with kids live longer</p><p>https://jech.bmj.com/content/71/5/424</p><p> </p><p> </p><p>How to contact Christian Benedict:</p><p>Email: [email protected]</p><p>LinkedIn: <a href="https://www.linkedin.com/in/christian-benedict-a25b1615a/" target="_blank" rel="ugc noopener noreferrer">https://www.linkedin.com/in/christian-benedict-a25b1615a/</a></p>
March 9, 2025
<p>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.</p><p><br></p><p>Chapters:</p><p>(0:00:12) Intro</p><p>(0:03:41) Christian Benedict’s career path</p><p>(0:13:06) What is sleep?</p><p>(0:24:09) Sleep stages & sleep quality </p><p>(0:34:06) Sleep quantity/duration</p><p>(0:42:08) Outro & Teaser to Part 2</p><p> </p><p>Studies that Christian refers to:</p><p>Aversive tobacco smoke during non-REM sleep</p><p>https://pubmed.ncbi.nlm.nih.gov/25392505/</p><p><br></p><p>Epileptic patients and sleep deprivation</p><p>https://pubmed.ncbi.nlm.nih.gov/29106402/</p><p><br></p><p>Correlations between time in different sleep stages and daytime alertness are not that good, contradictory evidence</p><p>https://pubmed.ncbi.nlm.nih.gov/10678518/</p><p><br></p><p>Epworthsleepiness scale and sleep stages are not well correlated</p><p>https://pubmed.ncbi.nlm.nih.gov/19110886/</p><p> </p><p>People struggling with sleep do not necessarily differ in PSG-derived sleep stage outcomes from normally sleeping people</p><p>https://pubmed.ncbi.nlm.nih.gov/29402512/</p><p> </p><p>Peer feedback can impact your retrospective judgement of your last night of sleep</p><p>https://pubmed.ncbi.nlm.nih.gov/24417326/</p><p>https://pubmed.ncbi.nlm.nih.gov/33204201/</p><p>American Society for Sleep Medicine, 7-9 hours, probably 6 and 10 hours are also fine</p><p><a href="https://www.thensf.org/wp-content/uploads/2020/10/NSF-SleepDurationTiming_Background-1200x1312-1.jpg">https://www.thensf.org/wp-content/uploads/2020/10/NSF-SleepDurationTiming_Background-1200x1312-1.jpg</a></p><p> </p><p>Shorter or longer than these 6-10 hours is mostly associated with poor health outcomes</p><p><a href="https://pubmed.ncbi.nlm.nih.gov/11825133/">https://pubmed.ncbi.nlm.nih.gov/11825133/</a></p><p> </p><p>Christian’s work on interindividual responses in brain health outcomes to sleep loss</p><p>https://pubmed.ncbi.nlm.nih.gov/36088460/</p><p> </p><p>Studies showing that people who think they cope well with sleep loss are actually not doing well</p><p>https://pubmed.ncbi.nlm.nih.gov/29383809/</p><p> </p><p>How to contact Christian Benedict:</p><p>Email: [email protected]</p><p>LinkedIn: <a href="https://www.linkedin.com/in/christian-benedict-a25b1615a/">https://www.linkedin.com/in/christian-benedict-a25b1615a/</a></p>
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