Occurrence of heatstroke cases and its association with meteorological factors in Baoshan District, Shanghai

Objective To analyze the occurrence of heatstroke cases in Baoshan District, Shanghai, in recent years and explore its association with meteorological conditions.

Methods Daily heatstroke case information and corresponding meteorological data from June 15 to September 30 during 2013-2022 were collected. An ordinal logistic regression model was used to estimate the strength of the association between heatstroke occurrence and meteorological conditions and to calculate temperature reference values for heatstroke warnings.

Results From 2013 to 2022, a total of 173 heatstroke cases were recorded in Baoshan District, with a male-to-female ratio of 6.2 : 1. The average age of heatstroke cases was (45.08 ±17.85) years old, with 114 cases (65.9%) occurring in July. Ordinal logistic regression analysis showed that for each 1% increase in relative humidity, the risk of heatstroke was reduced to 0.901 times the original risk. Compared to non-rainfall days, the risk of heatstroke during rainfall days was reduced to 0.340 times the original risk. For each 1 ℃ increase in daily average temperature, daily maximum temperature, or daily minimum temperature, the risk of heatstroke increased to 2.005, 1.736, and 1.906 times the original risk, respectively. The risk of heatstroke during heatwave and high-temperature days increased to 11.896 and 15.819 times, respectively, compared to non-heatwave and non-high-temperature days. For the 3-day moving average temperature (i.e., the average temperature of the current day and the previous two days), each 1 ℃ increase in daily average temperature, daily maximum temperature, and daily minimum temperature increased the risk of heatstroke to 1.926, 1.699, and 1.957 times, respectively. All these differences were statistically significant (all P < 0.05). The daily average temperature, daily maximum temperature, and daily minimum temperature for the extreme heatstroke risk warning values are 35.55℃, 40.58℃, and 31.07℃, respectively. The three temperature meteorological conditions for the high heatstroke risk warning values are 28.87℃, 33.31℃, and 25.21℃, respectively.

Conclusions July was the peak period for heatstroke in Baoshan District. Increases in daily average temperature, daily maximum temperature, and daily minimum temperature all increased the likelihood of heatstroke, with sustained relatively high daily minimum temperatures over 3 days being more likely to result in heatstroke.