Effect of Seasonal Variation on the Incidence of Urolithiasis at an Urban Academic Medical Center
Gianpaolo Carpinito, BA; Alysen Vilhena, BA; David S. Wang, MD; Richard K. Babayan, MD; Shaun E. Wason, MD
Boston University School of Medicine, Boston, MA
Background
Interest in the effect of seasonality and temperature on the incidence of symptomatic urolithiasis has increased in recent years. To date, most studies have overwhelmingly demonstrated a positive correlation between incidence of urolithiasis and warmer times of year or higher ambient temperatures. Due to unique factors within our patient population, we suspect that the incidence of symptomatic urolithiasis may not follow this commonly observed trend. Our institution is a not-for-profit 487-bed academic medical center serving a diverse patient population, many of whom are from the Caribbean and Latin America. We sought to determine whether season, month, and/or average monthly temperature had any effect on symptomatic urolithiasis.
Methods
All ureteroscopies performed at our institution for stone disease between July 1st 2016 and June 30th, 2017 were reviewed. Demographic data, including race and ethnicity, as well as stone characteristics were extracted. Average monthly temperature in Boston was obtained from the National Oceanic and Atmospheric Administration records.
Results
275 ureteroscopies were performed for stone disease between July 1st, 2016 and June 30th, 2017. 51.3% were male, average patient age was 49.2 ± 15.3 years and average BMI was 29.2 ± 6.69. By race, 37.5% were white, 29.1% black/African-American, 4.4% Asian, 3.3% Hispanic/Latino, and 25.5% were unknown/unreported. Most patients had multiple stones (62.1%), located intrarenally (40.7%) and the average diameter measured 7.61 ± 4.56 mm. Stone type was predominantly calcium oxalate (78.8%). The highest average monthly temperature occurred during August 2016 (76.4oF) and the lowest in March 2017 (34.0oF). There was significant variation in the incidence of ureteroscopies by month χ2(11)=21.68, p=.027), with the greatest percentage of ureteroscopies occurring in November (12.7%) and the smallest percentage occurring in May and July (5.1%). The incidence of ureteroscopies did not vary by season [χ2(3)=1.09, p=0.78] or by average monthly temperature [r(10)= −.35, p=.27].
Conclusion
Although there was no clear relationship between the incidence of ureteroscopy and season or average monthly temperature, interestingly, we found that a large volume of ureteroscopies were performed in cooler months and a smaller number in warmer months. This is in contrast to previously published trends and warrants further examination.
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