Lunar Tractive Forces and Renal Stone Incidence

Background. Several factors are implicated in renal stone formation and peak incidence of renal colic admissions to emergency departments (ED). Little is known about the influence of potential environmental triggers such as lunar gravitational forces. We conducted a retrospective study to test the hypothesis that the incidence of symptomatic renal colics increases at the time of the full and new moon because of increased lunar gravitational forces. Methods. We analysed 1500 patients who attended our ED between 2000 and 2010 because of nephrolithiasis-induced renal colic. The lunar phases were defined as full moon ± 1 day, new moon ± 1 day, and the days in-between as “normal” days. Results. During this 11-year period, 156 cases of acute nephrolithiasis were diagnosed at the time of a full moon and 146 at the time of a new moon (mean of 0.4 per day for both). 1198 cases were diagnosed on “normal” days (mean 0.4 per day). The incidence of nephrolithiasis in peak and other lunar gravitational phases, the circannual variation and the gender-specific analysis showed no statistically significant differences. Conclusion. In this adequate powered longitudinal study, changes in tractive force during the different lunar phases did not influence the incidence of renal colic admissions in emergency department. 1. Introduction Kidney stone formation is usually due to environmental, metabolic, or genetic factors. A precise causative factor is not identified in most nephrolithiasis patients. A family history of kidney stones, insulin resistance, hypertension, obesity, low urine volume, and dietary habits is associated with an increased risk [1]. Stone disease also shows marked geographic variability, and the phenomenon of the “stone season” has been attributed to both increased environmental temperatures and sunlight levels [2]. The expected environmentally related increase in the prevalence of nephrolithiasis can cause a significant increase in renal colics admissions, with the corresponding strain on healthcare delivery and related costs [3]. Apart from this well-known risk factor, little is known about the impact of other potential triggers on nephrolithiasis, such as lunar gravitational forces. The lunar phases have been held responsible for affecting human health since antiquity. The effect of the lunar phases on human physiology is well documented, and relevant studies have shown an associated increase in seizures, deregulation of the cardiovascular system, aggressive behavior, changes in menstruation, and spontaneous full-term deliveries [4–8]. Studies