Call it howling at the moon, but the timing of aortic dissection surgery within the lunar cycle may influence the odds of death and length of stay, according to a study published online July 9 in Interactive CardioVascular and Thoracic Surgery.

Seasonal effects on cardiovascular health have been studied in the past, Jeffrey H. Shuhaiber, MD, of the cardiothoracic surgery department of Rhode Island Hospital in Providence, and colleagues pointed out, but little is known about the potential influence of lunar cycle phases. They prospectively collected data on cardiac surgery patients who underwent acute aortic dissection (AAD) operations at two hospitals between 1996 and 2011 to study the temporal effects of seasonal and lunar cycles on mortality and length of stay.

They identified 210 patients; 109 of whom had AAD repair only and 101 had AAD repair and aortic valve surgery or CABG or both. Survivors were younger and less likely to have diabetes.

Mortality predictors included age and procedure done during a full-moon phase. Procedures done during the full-moon phase were associated with a significantly shorter length of stay compared with those done during the new moon phase.

Shuhaiber et al found that the odds of dying after AAD surgery were twice as high as during the winter compared with other seasons, but the finding was not statistically significant.

The authors cited research that found increases in intracranial bleeds with a new moon and highest incidence of intracranial aneurysm during the new moon phase.

“It is possible that the explanations already investigated for intracranial aneurysm rupture and stroke frequency could also apply to cardiac surgery,” they wrote. “The stressful effect of surgical intervention could be more hazardous within a particular lunar phase cycle because of the altered disease behaviour seen in acute aortic dissection. However, the true underlying mechanisms for such remain elusive.”

They acknowledged that their study was missing variables such as seasonal affective disorder and that the sample sizes within the four moon phases were small. In a release, Frank Sellke, MD, chief of cardiothoracic surgery at the Cardiovascular Institute at Rhode Island Hospital, emphasized that procedures cannot always be timed around the lunar cycle.

“But better understanding the effects of the environment—including seasonal and lunar cycles—on our health can help us to better understand these rhythms, and ultimately provide better care for our patients.”

Shuhaiber is now with the Cleveland Clinic, according to the release.