No association of moon phase with stroke occurrence

ABSTRACT

Stroke occurrence shows strong correlations with sleep disorders and even subtle sleep disturbances have been shown to affect ischemic stroke (IS) occurrence. Chronobiology also exerts effects, like the morning surge in IS occurrence. Lunar cycles have also been shown to affect sleep and other physiological processes, but studies on moon phases and its possible association with occurrence of stroke are rare and nonconclusive. Therefore, we studied the effects of moon phases on stroke hospitalizations and in-hospital mortality nationwide in Finland in 2004–2014. All patients aged ≥18 years with IS or intracerebral hemorrhage (ICH) as primary discharge diagnosis were included. Daily number of admissions was treated as a response variable while moon phase, year and astronomical season were independent variables in Poisson regression modeling. We found no association between moon phases and stroke occurrence. The overall occurrence rates did not vary between different moon phases for IS or ICH (p = 0.61 or higher). There were no differences between moon phases in daily admission rates among men, women, young and old patients for any of the stroke subtypes. There was no difference in in-hospital mortality with regard to moon phase for IS or ICH overall (p = 0.19 or higher), nor in subgroup analyses. There were no significant interactions between moon phase and astronomical season for stroke occurrence or in-hospital mortality. To conclude, in this over a decade-long nationwide study including a total of 46 million person years of follow-up, we found no association between moon phases and occurrence or in-hospital mortality rates of IS or intracerebral hemorrhage.

KEYWORDS:

• Circadian rhythms
• intracerebral hemorrhage
• ischemic stroke
• lunar phase
• seasonality

Declaration of interest

Jori Ruuskanen has obtained honoraria for scientific presentations and attended conferences at the cost of a pharmaceutical companies (Baxter, Bayer, Biogen Idec Finland, Boehringer Ingelheim, Genzyme, GSK, Lundbeck, Merck, Merck Serono, Novartis, Roche, Sanofi-Aventis, Orion Pharma, Teva, and UCB Pharma).

Jussi Sipilä has attended conferences at the cost of a pharmaceutical company (Orion Corporation, Lundbeck, Sanquin, Merck Serono, Novartis, Sanofi), received honoraria (Pfizer, Merck) and holds shares (Orion Corporation).

Päivi Rautava has attended a conference at the cost of pharmaceutical company (Roche).

Ville Kytö has obtained honoraria for scientific presentations (Bayer, Boehringer Ingelheim, Orion Pharma) and consultation (Bayer) and attended conferences at the cost of a pharmaceutical companies (Bayer, Boehringer Ingelheim, AstraZeneca).

The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This study was funded by the governmental VTR-funding of the hospital district of Southwestern Finland and grant funding of the Finnish Cardiac Society.