Physical activity, sleep duration and metabolic health in children fluctuate with the lunar cycle: science behind the myth

Abstract

Behaviours of several animal species have been linked to lunar periodicity. Evidence for such links in humans is weak; however, recently, shorter sleep duration was reported around full moon in two small samples of adults. As restrictions in sleep duration have been shown to adversely affect glucose regulation and physical activity to improve glucose regulation, one could speculate that cardiometabolic risk factors might also be affected by the lunar phase. We retrospectively examined 795 Danish children, aged 8–11 years, with more than 13 000 24-h accelerometer recordings of activity and sleep as well as 2000 measurements of different cardiometabolic risk factors, including insulin sensitivity, appetite hormones and blood pressure, during nine lunar phases. During the period around full moon, children were 5.0 and 3.2 min per day less active, slept 2.4 and 4.1 min per night longer, had 0.03 and 0.05 higher homeostatic model assessment of insulin resistance and 0.6 and 0.8 mmHg higher mean arterial blood pressure compared with days around half moon and new moon, respectively (all P ≤ 0.02). Furthermore, ghrelin was lower and leptin was higher during the period around full moon compared with days around half moon (both P < 0.001). The results suggest that physical activity rather than sleep is responsible for the metabolic alterations observed around full moon. However, we have no understanding of potential mechanisms that may mediate a potential true link between childhood behaviour and the lunar cycle or confounders that may explain this, apparently leading to fluctuation in a number of cardiometabolic risk markers conjointly with lunar phases.

Physical activity, subjective sleep quality and time in bed do not vary by moon phase in German adolescents

“…Observed levels of MVPA were very similar between our study and that of Sjödin et al . (), whose population is the most similar to our own; and we confirm the well‐known tendency of adolescents to report more, and better, sleep on weekends.…”

“…() found no lunar periodicity in adults' physical activity, which suggests that the link between physical activity and sleep found by Sjödin et al . () is also not always present. However, studies differ from each other in methods and population, and therefore some heterogeneity is to be expected.…”

“…Many studies (Smith et al ., ) take place in sleep labs, which allow objective measurement of sleep characteristics and exclude moonlight as a possible driver of the effects: however, these tend to be small and thus perhaps confounded by secular variation. Conversely, larger studies (Sjödin et al ., ) generally lack objective measurements of sleep, and instead rely on self‐reported sleep duration and quality.…”

“…At least one such study (Smith et al, 2014) not only found that adults slept less at full moon, but also had higher cortical reactivity. However, this is not always the case: one large study of children (Sj€ odin et al, 2015) found full moon to be associated with more sleep, not less. This study also observed a relationship with daily moderate-tovigorous physical activity (MVPA), and suggested sleep quality as a possible intermediary.…”

Sleep, circadian dysrhythmia, obesity and diabetes

“…From the first human experimental work of Jurgen Ashoff emerging studies suggest the role of lunar cycles could also be involved, operating through changes in physical activity[6,7]. …”