Can camping reset melatonin production?

Relation

Stothard ER, McHill AW, Depner CM, et al. Circadian entrainment to the natural light-dark cycle across seasons and weekends.Curr Biol. 2017;27(4):508-513.

Design and participants

• Studie 1: Fünf (1 Frau, 4 Männer, Alter 30,4 ± 8,6 Jahre) gesunde, körperlich aktive Personen nahmen an dem zweiwöchigen Experiment teil, das um die Wintersonnenwende in Boulder, Colorado stattfand. Während der ersten Woche zeichneten die Teilnehmer regelmäßige tägliche Schlaf- und Wachzeiten in ihrer häuslichen Umgebung unter Verwendung ihrer typischen selbstgewählten künstlichen Nachtlichtgewohnheiten (ALAN) auf. Die zweite Woche war ein Outdoor-Campingerlebnis in den Rocky Mountains, wo nur natürliches Licht (dh Sonnenlicht, Mondlicht und Lagerfeuer; keine Taschenlampen, Laternen oder elektrischen Geräte) erlaubt war.
• Studie 2: Vierzehn (7 Männer, 7 Frauen, Alter 28,4 ± 8,8 Jahre) gesunde, körperlich aktive Personen nahmen an einem einwöchigen Experiment teil, das um die Sommersonnenwende in Boulder, Colorado, stattfand. Während der Woche zeichneten die Teilnehmer anhand ihrer typischen selbstgewählten ALAN-Gewohnheiten regelmäßige tägliche Schlaf- und Wachzeiten in ihrer häuslichen Umgebung auf. Am Wochenende ging die Versuchsgruppe (n=9) zu einem zweitägigen Campingerlebnis in den Rocky Mountains (Taschenlampen waren erlaubt). Die restlichen Teilnehmer blieben über das Wochenende in ihrer heimischen ALAN-Umgebung.

Target parameters

• Nächtliche Melatoninspiegel (einschließlich Beginn, Mittelpunkt und Endpunkt)
• Nachtschlafplan (einschließlich Dauer, Beginn und Ende)

Key insights

In Study 1, winter camping participants' mean melatonin onset times occurred 2.6 hours earlier than their individual baseline ALAN times (P=0.017, effect sizeη²_G=0.57). This delay increased from baseline (i.e., mean melatonin onset time was successively earlier) on each day of the 6-day camping experience as participants acclimated to a more natural pattern of melatonin production.

Melatonin use during winter camping was significantly earlier and sleep time was significantly increased compared to a similar summer camping experience (sleep time: 10.0 ± 1.8 hours vs. 14.4 ± 2.8 hours,P<0.025, effect sizeη²_G=0.53). In contrast, there were no significant differences in melatonin or sleep times between the winter and summer ALAN groups, demonstrating the balancing effect of modern lighting on natural seasonal circadian rhythms.

These two small experiments demonstrate applications of the general philosophy of naturopathy - namely, working in harmony with the cycles of the natural world.

In Study 2, mean melatonin onset and midpoint times for Study 2 participants were on average 1.4 and 1.0 hours earlier, respectively, than their individual baseline times from the previous week (P<0.01; Effect sizesη²_G=0.45 or 0.20), although the sleep pattern did not change. Participants in the ALAN baseline group had mean delays of approximately 1.0 hour for melatonin onset and onset, reflecting the greater social activities (e.g., being with friends, watching television/movies) reported by participants.

Practice implications

These studies are the first to use a controlled experimental method to demonstrate that real-world ambient light exposures (compared to laboratory-induced changes) influence melatonin onset time in humans. Study 1 definitively shows that natural patterns of melatonin production can vary seasonally between the winter and summer months, with corresponding changes in sleep duration, in contrast to the typical melatonin and sleep patterns resulting from ALAN exposure in modern society that are constant year-round.

Study 2 shows that the shift in circadian melatonin patterns can occur quickly over a single weekend when exposed to natural or artificial light patterns.

These two small experiments demonstrate applications of the general philosophy of naturopathy – namely, working in harmony with the cycles of the natural world and naturecompared to medicatrix naturae(the healing power of nature).

Prolonged melatonin production and sleep times during the winter months confer evolutionary advantages in regulating hormones, neurotransmitters, and the immune system.¹This has clinical implications for mental illnesses (e.g. seasonal affective disorder).²and autoimmune diseases (e.g. multiple sclerosis).³Of course, the circadian cycle of melatonin production is known to influence a variety of other health-related outcomes, particularly insomnia and sleep-wake cycle disorders⁴and cancer, particularly breast cancer (as reported in a previous issue of Natural Medicine Journal).⁵Other health conditions known to be affected by circadian disruption include adrenal insufficiency, insulin/blood sugar regulation, weight control/obesity, high blood pressure, cognitive function, Parkinson's disease and asthma.⁶

Limitations of this study include the very small sample size, lack of randomization, and participant self-selection. Anyone who agrees to camp in Colorado for a week in late December is likely to belong to a unique subset of the population and may not have physiological (or psychological) responses that are representative of a larger general population. However, the results of these studies confirm decades of studies on circadian rhythms in other mammals. Further research is needed to verify the clinical utility of this work.

Conclusion

Human circadian rhythms can fluctuate greatly depending on the season and natural and artificial ambient light. Although not everyone is a candidate for 6 days of winter camping in the Rocky Mountains, it is likely that everyone could benefit from adjusting their ALAN schedule to be more in harmony with the natural light and dark cycles of the seasons.