Season 4 – Episode 1: Why biological timing matters in medicine

Is there a best time for a vaccine? In this episode of Light O'Clock, we speak with Dr Cathy A. Wyse about whether the time of day when we receive a vaccine can influence how we respond to it. We first discuss how circadian rhythms shape the immune system, how vaccines work, and the difference between vaccine response (e.g., antibody levels) and vaccine effectiveness (i.e., protection against infection or disease). We then discuss why the current evidence remains mixed and how factors such as chronotype, sleep, age, sex, prior immunity, and vaccine type may influence results. Paper reference: https://doi.org/10.1177/07487304241232447 The key message: the immune system is rhythmic, so timing could matter -- but the evidence is not yet strong enough to recommend one specific time of day for vaccination. For now, the most important advice remains: get vaccinated when you can.

In the first episode of Season 4, we start with the foundations of circadian medicine. Together with our guest Henrik Oster, we take a tour through the circadian system and ask what biological timing has to do with health and disease. We discuss how the body coordinates different physiological and behavioural functions across the 24-hour day, what can happen when internal rhythms become disrupted, and why timing may matter in medicine. We then introduce three key ideas in circadian medicine: exploiting the clock to optimise the timing of treatments, targeting the clock as part of therapy, and detecting the clock to better personalise healthcare. Finally, we examine the current state of the field, the challenges of integrating circadian principles into clinical practice, and the future of circadian medicine. This episode sets the stage for the rest of the season, where we will explore specific areas of circadian medicine in more detail – from vaccines and cancer care to neonatal health, metabolism, exercise, and shift work. Stay tuned!

Light O'Clock is back with Season 4! In this new season, we explore how biological timing shapes health and disease, and how accounting for circadian rhythms may help improve prevention, diagnosis, and treatment. We will discuss topics such as immunity and vaccination, cancer care, neonatal health, metabolism, exercise, and shift work. Join us as we take a tour through the emerging field of circadian medicine, and ask what it could mean for the future of healthcare.

In the final episode of this mini-series, Caro, Anna, and Priji explore how the built environment shapes our interactions with daylight. From balconies and windows to schools, workplaces, and public spaces, the places we move through every day influence how much natural light we receive and how we experience it. These spaces are more than design choices. They are shaped by culture, climate, geography, and daily routines. Together with our interviewees, we discuss how architecture can either support or limit our relationship with daylight, and why paying attention to light in our environments matters for well-being, mood, and everyday life. Key highlights from this episode: How homes, workplaces, and schools affect daylight exposure Why balconies and "transitional spaces" can feel so meaningful The role of window design and orientation (we even get poetic about windows!) How thoughtful design can help us build a healthier relationship with daylight Links and resources: Anna and Priji’s publication describing their framework: https://doi.org/10.1038/s44271-024-00159-5 Visualisation of the framework’s “bubbles”: https://www.nature.com/articles/s44271-024-00159-5/figures/3 More about the Daylight Academy (DLA) Project: https://daylight.academy/projects/daylight-interactions/

In the second episode of our Interacting with Daylight mini-series, Caro is joined by Anna and Priji again to explore how cultural traditions and individual behaviours shape our interactions with daylight. Building on the previous discussion of location, this episode shifts the focus to how social norms, gender roles, and cultural traditions shape people’s experiences and interactions with daylight. Links and resources: Anna and Priji’s publication describing their framework: https://doi.org/10.1038/s44271-024-00159-5 Visualisation of the framework’s “bubbles”: https://www.nature.com/articles/s44271-024-00159-5/figures/3 More about the Daylight Academy (DLA) Project: https://daylight.academy/projects/daylight-interactions/ Timestamps: (00:00) Intro (01:23) What do we mean by culture and behaviours (03:53) Snippets: solar eclipse and Norwegian winter (08:40) Yellow dishes & the sun (12:10) Snippets: Daylight in Spain vs Norway (19:30) Snippets: Sun exposure, skin care, and lunch habits in Rochester (20:20) Snippets: Clothing & sun umbrellas (25:00) Gender roles and exposure to daylight (32:57) Focus group snippets: Cultural differences around daylight (43:57) Snippets: Playing as kids — outdoor and indoor behaviours (47:50) Snippets: Schools and daylight habits in schools in different countries (51:54) Reflections on outdoor/indoor habits in schools (55:40) Outro: how different languages refer to (day)light

In this first episode of our new Interacting with Daylight mini-series, your host Caro is joined by Anna and Priji to discuss the Daylight Interaction Project, funded by the Daylight Academy. The project explores how people interact with daylight in everyday life and how this is shaped by factors such as location, built environments, culture and behaviours. The episode focuses on the first part of their framework: Location. Through interview snippets recorded during the Daylight Academy Summer School in beautiful Chexbres, Switzerland, the hosts reflect on how geography, climate, temperature and landscape can influence experiences of daylight. Interviewees come from diverse locations and latitudes: Singapore, Norway, Rochester (USA), and Costa Rica — offering perspectives on topics such as seasonal daylight changes, tropical versus northern light environments, and associations with sunlight and darkness. Links and resources: Anna and Priji’s publication describing their framework: https://doi.org/10.1038/s44271-024-00159-5 Visualisation of the framework’s “bubbles”: https://www.nature.com/articles/s44271-024-00159-5/figures/3 More about the Daylight Academy (DLA) Project: https://daylight.academy/projects/daylight-interactions/ Timestamps: (00:00) Intro: the Daylight Interaction Project (10:20) Project summary and interviewees (13:51) Geolocation: latitudes, climatic zones, seasons, geographical context (19:51) Snippets: associations with daylight and darkness (30:50) Daylight as a placemaking tool (34:21) Daylight vs sunlight (37:55) Snippets: Seasonal changes and colours (53:05) Reflections on seasonality (59:33) Episode summary (01:02:00) Outro: darkness associations

In this special episode of Light O’Clock, we share snippets from our very first live recording, captured on stage at Buch Wien in Vienna in November 2025. Host Caro Guidolin and her colleague Marie-Luise Schreiter answer audience questions on chronotype, light exposure, sleep, shift work, and why people feel more tired in winter.

Many people notice changes in mood, energy, and motivation during the dark winter months. In this episode, we explore Seasonal Affective Disorder (SAD) and the broader experience of feeling low in winter and, importantly, what science-backed strategies can help. We speak to Delainey Wescott about changes in sleep and circadian rhythms in SAD, and chat with Hester Parr and Hayden Lorimer about the Wintering Well project — an initiative that highlights the power of community, shared experiences, and collective coping during the darker months. Throughout the episode, we discuss practical approaches to winter wellbeing, including light exposure, daily routines, cognitive reframing of winter, and small habits that can make a meaningful difference. Links and resources: Sleep in seasonal affective disorder: https://doi.org/10.1016/j.copsyc.2019.08.023 Retinal light sensitivity in summer and winter: https://doi.org/10.1016/j.jad.2021.04.084 Wintering Well resources (Living with SAD project): https://www.gla.ac.uk/research/az/livingwithsad/winteringwell/resources/. Includes: the guidebook Light is a Right: A Guide to Wintering Well, an online course developed by CBT experts, the Wintering Together Toolkit, and the SAD Stories Exhibition. Timestamps: (02:24) What is SAD and how is that different from the winter blues? (05:16) Geography matters: who is affected by SAD? (06:50) Circadian rhythms and sleep in SAD (09:38) Light sensitivity in SAD (11:50) Evidence-based strategies to alleviate SAD symptoms (17:30) Summary (18:35) The Living with SAD project (22:30) Wintering Well Workshops (25:45) My patch of winter sky, writing a letter to winter, and my kind of winter neighbourhood (34:00) Winter Well resources created by the workshops (36:28) The present and future of the Living with SAD project (39:45) Wrap up and outro

Light O’Clock is going live from Vienna at Buch Wien 2025 on Saturday, 15 November – and this time, you set the agenda for the episode! Together with Marie Luise Schreiter, we’ll be diving into your questions about how light shapes our brains, bodies, health, and daily rhythms – live on stage. What have you always wanted to know about light, sleep, or circadian rhythms? Send us your question through this link: https://form.jotform.com/252533837926365

For our Season 3 finale of Light O’Clock, we dive into a timely and often overlooked issue: light pollution. Artificial light at night has become a constant in modern life — but what are the hidden consequences? Our guests, Barbara Harding, Travis Longcore and Karolina M. Zielińska-Dąbkowska, bring scientific insight into how nighttime light exposure may affect human health, including possible links to cancer, and how it disrupts wildlife, ecosystems, and natural rhythms. We also explore practical solutions: since we can’t simply switch off the lights, how can we use artificial light more responsibly to protect both ourselves and the environment? We explain the five principles for responsible outdoor lighting created by International DarkSky Association (now DarkSky International) and the Illuminating Engineering Society. Links and resources DarkSky International website: https://darksky.org/ Ecological light pollution: https://doi.org/10.1890/1540-9295(2004)002[0191:ELP]2.0.CO;2 Five principles for responsible outdoor lighting: https://darksky.org/resources/guides-and-how-tos/lighting-principles/ Outdoor artificial light and cardiometabolic risk: https://doi.org/10.1093/aje/kwae269 Artificial light at night and cancer risk: https://doi.org/10.1016/j.scitotenv.2024.177059 Timestamps (00:00) What is light pollution? (02:17) Light at night and circadian rhythms (05:18) Light at night and cancer risk (09:35) How light pollution is measured (16:11) What's the link between light at night exposure and disease risk? (19:00) Ecological light pollution (20:50) Effects of light pollution in animals: birds and turtles (26:00) Artificial light and animals' circadian rhythms (28:55) Light pollution changing predators-preys dynamics (32:30) Awareness towards light pollution in different countries (35:20) Why did we start to use artificial light in the first place? (40:30) What are the current lighting standards? (43:00) Different stakeholders involved in outdoor lighting (47:00) Five principles for responsible outdoor lighting (55:20) Wrap up and outro