Elsevier

Epilepsy & Behavior

Volume 13, Issue 3, October 2008, Pages 549-550
Epilepsy & Behavior

Brief Communication
Moonstruck? The effect of the lunar cycle on seizures

https://doi.org/10.1016/j.yebeh.2008.06.009Get rights and content

Abstract

Recent reports on the effects of the lunar cycle on seizure occurrence have yielded mixed results. If the moon phase is influential, we hypothesized that this would be due to the moon’s contribution to nocturnal illumination, rather than its waxing or waning state, and that significant correlations would not be apparent if local cloud cover were controlled for. We found a significant negative correlation between the mean number of seizures and the fraction of the moon illuminated by the sun (ρ = –0.09, P < 0.05) in 1571 seizures recorded in a dedicated epilepsy inpatient unit over 341 days. This correlation disappeared when we controlled for the local clarity of the night sky, suggesting that it is the brightness of the night and the contribution the moon phase makes to nocturnal luminance, rather than the moon phase per se, that may influence the occurrence of epileptic seizures.

Introduction

Superstitions regarding the influence of the moon on many conditions, including epilepsy, date back to antiquity. Many of the remedies for epilepsy recommended by Pliny the Elder more than 2000 years ago, ranging from the ingestion of camel brains to a helping of lion fat garnished with fennel, were to be taken at specific times during the lunar cycle to maximize their efficacy. The idea that the moon can influence human behavior remains popular to this day, and these beliefs are particularly prevalent among nurses and mental health professionals [1].

Recent studies of the effect of the moon on seizure occurrence have yielded mixed results. Polychronopoulos et al. [2] found an increase in emergency room admissions for seizures during the full moon quarter in a series of 859 patients. Conversely, Ruegg et al. [3] reported a peak in episodes of status epilepticus in the opposite phase of the lunar cycle, 3 days after a new moon. Benbadis et al. [4] failed to find an increase in epileptic seizures in people with an established diagnosis of epilepsy at the time of the full moon, but reported that such increases were more likely to occur in the final quarter of the lunar phase.

Discrepancies in the reports of an increase in seizures related to the moon phases suggest that it is an inconsistent phenomenon and may simply reflect statistical probability combined with a publication bias toward positive findings. Nevertheless, a number of theories have been developed to explain these apparent lunar effects. These range from rather unlikely putative explanations involving the gravitational effect of the moon on the water mass of the body and brain and cerebral reactions to changes in the earth’s electromagnetic field [5] to the nocebo effect of patients’ expectations of seizures creating self-fulfilling prophesies.

Before the advent of modern lighting, the brightness of the moon at night undoubtedly played an important role in shaping human behaviors by allowing after-dark activities at certain times and not others. The effects of nocturnal illumination on the sleep–wake cycle have been postulated as the genesis of many of the ancient associations of the moon with madness and epilepsy that continue to this day [6]. In modern urban living, the effects of the moon on nocturnal illumination are greatly reduced. Nevertheless, a recent sleep study reported that normal healthy individuals slept, on average, 20 minutes less and that their morning fatigue was greater during the full moon phase than during the new moon [7].

If the moon phase does have an effect on the frequency of epileptic seizures, we hypothesized that this would be due to the moon’s contribution to nocturnal illumination rather than its waxing or waning state. The traditional phases of the moon were determined millennia ago using essentially arbitrary cutoffs, based on the angle of the sun and moon to the earth. In this study, we therefore used a precise measure of the fraction of the moon illuminated by the sun to determine the brightness of the moon on each day of our study and controlled for the effects of contemporaneous, local cloud cover on this illumination.

Section snippets

Lunar measures

The percentage of the moon’s surface illuminated by the sun is a more sophisticated, quantitative measure of the moon’s appearance than the phase. Like the phase, the percentage of the moon illuminated is the same regardless of the observer’s position on earth. Data on the fraction of the moon visible from the earth from January to December 2006 were provided by the Astronomical Applications Department of the U.S. Naval Observatory.

Clear skies

The amount of light received on the earth’s surface from the

Bright nights

There was a significant negative correlation between the mean number of epileptic seizures per 24 hours and the fraction of the moon illuminated during that period (Spearman’s ρ = −0.09, P < 0.05). Conversely, the frequency of unclassified seizures was positively correlated with the fraction of the moon illuminated (ρ = 0.17, P < 0.01).

These findings suggest that although epileptic seizures are less likely to occur on brighter nights, the frequency of unclassified events increases.

Partial correlations

Discussion

There is no relationship between the fraction of the moon illuminated and the frequency of epileptic seizures when the overall brightness of the night sky is controlled for. This suggests that it is the brightness of the night and the contribution the moon phase makes to that, rather than the phase of the moon per se, that may have an influence on the frequency of epileptic attacks. Epileptic seizures were more likely to occur on dark nights than brighter nights. This would be consistent with

Acknowledgment

The authors are grateful to Jane Yeomans and the nursing team on the Gowers Epilepsy Assessment Unit at the National Society for Epilepsy for their diligence in keeping the seizure logs used in this study.

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