High ambient temperature increases the number of emergency visits for upper urolithiasis in Hefei City, China

BACKGROUND: Few studies have examined the effect of ambient temperature on upper urolithiasis in developing countries, with even fewer considering individual factors. METHODS: The present study analyzed data on emergency department visits for upper urolithiasis from three hospital sites of a large hospital in Hefei, China, during 2016–2020. Data on environmental factors during the same period were also analyzed. A time series analysis employing a generalized Poisson regression model (GPRM) combined with a distributed lag non-linear model (DLNM) was conducted to evaluate the effect of ambient temperature on the number of emergency department visits for upper urolithiasis. RESULTS: We found that ambient temperatures above 9 °C were positively associated with the frequency of upper urolithiasis visits, with the relationship being most significant on the current day and with a one-day lag. In the single-day lag effect, the most significant relative risk (RR) for mild heat (75th percentile) and high heat (95th percentile) was 1.229 (95% CI: 1.100–1.373) and 1.337 (95% CI: 1.134–1.577), respectively. The cumulative lag effect was significantly higher than the single-day lag effect, with maximum relative risks (RRs) of 1.779 (95% CI: 1.356–2.335) and 2.498 (95% CI: 1.688–3.697), respectively. The maximum lag time was 7 days. RRs were also higher among women and individuals aged 30–44 years. CONCLUSIONS: Increased ambient temperature is a risk factor for upper urolithiasis, and there is a hysteresis effect. Women and individuals aged 30–44 years are the most susceptible.