The influence of seasons and lunar cycle on hospital outcomes following ascending aortic dissection repair

Abstract

Objectives: The effect of the lunar cycle and seasonal variation on ascending aortic dissection surgery outcomes is unknown. We investigated these temporal effects on risk-adjusted hospital mortality and then on the length of stay (LOS) following surgery for survivors.

Methods: We examined prospectively collected data from cardiac operations at two major centres within a single state between January 1996 and December 2011. We first examined the relationship between the lunar cycle and seasonal variation, along with demographic and risk profile covariates, with mortality using univariate analyses, followed by multiple logistic regression modelling that controlled for demographic and patient risk variables including age, gender, risk profile (diabetes, hypertension, dyslipidaemia and renal failure), and two surgical groups: Group A, consisting of patients having repair of ascending aorta dissection repair only, and Group B, with those having ascending aorta repair plus aortic valve surgery or coronary bypass surgery or both. We further examined the relationship with LOS using both univariate and multiple regression analyses.

Results: There were 210 patients who had repair of dissection in the study period, with 109 patients in Group A and 101 in Group B. The average age of this sample was 59.5 (standard deviation = 16.0), 65.7% were male and 18.1% died prior to discharge following repair. The greatest percentage of deaths occurred in winter (31.6%, n = 12), while the least were in summer (21.1%, n = 8) and fall (21.1%, n = 8). An overall χ(2) test found there was no difference in mortality for season (P = 0.55). Univariate analyses also found the age of patients who died vs lived was significantly higher (65.9 vs 58.1 years; P = 0.001), and a significantly greater (P = 0.029) percentage of patients with diabetes vs without diabetes died (41.7 vs 16.7%). Univariate analyses found all other covariates were not significantly related to mortality. In the multiple logistic regression model, there was no significant effect for season, while the odds of dying increased with age (odds ratio [OR] = 1.04, 95% confidence interval [95% CI] = 1.01-1.07, P = 0.012), and the odds of dying in the full-moon cycle vs the new moon cycle was significantly reduced (OR = 0.21, 95% CI = 0.05-0.81, P = 0.024). No other covariate significantly increased or decreased the odds of death, including diabetes risk, which had been significantly related to death in the univariate analysis. Within a linear regression model that examined the relationship with LOS, Group B (P = 0.020), male sex (P = 0.036) and the full-moon lunar phase (P = 0.001) were significantly related to shorter LOS.

Conclusions: Season had no effect on mortality or LOS following aortic dissection repair, while patient age significantly increased the odds of death. The full-moon cycle appeared to reduce the odds of death, and the full-moon cycle, along with being male and requiring a concomitant cardiac procedure, was associated with shorter LOS.

Keywords: Aortic dissection; Environmental factors; Outcomes; Pathophysiology risk factors; Surgery.