Ischemic stroke hospital admission associated with ambient temperature in Jinan, China

Abstract

Background: This study estimated the effects of ambient temperature and relative humidity on hospital admissions for ischemic stroke during 1990-2009 in Jinan, China.

Methods: To account for possible delayed effects and harvesting effect, we examined the impact of meteorological factors up to 30 days before each admission using a distributed lag non-linear model; we controlled for season, long-term trend, day of week and public holidays in the analysis. Stratified analyses were also done for summer and winter.

Results: A total of 1,908 ischemic stroke hospital admissions were observed between 1990 and 2009. We found a strong non-linear acute effect of daily temperatures on ischemic stroke hospital admission. With the mean temperature 15°C as the reference, the relative risk (RR) was 1.43 (95% confidence interval (CI): 1.10-1.85) for 0°C daily temperature on the same day, and 0.43 (95% CI: 0.31-0.59) for 30°C daily temperature on the same day, respectively. The effect of ambient temperature was similar in summer and winter. No significant association was observed between relative humidity and ischemic stroke hospitalization.

Conclusions: Low temperature might be a risk factor for ischemic stroke, and high temperature might be protective factor of ischemic stroke occurrence in Jinan, China.

Figure 1. Location of the study area in China.

Figure 2. The time series of monthly ischemic stroke hospital admission in Jinan, 1990–2009.

Figure 3. The time series of daily weather variables in Jinan, 1990–2009.

Figure 4. Three-D plot of RR along temperature and lags with 15°C as reference (left); and relative humidity and lags with 57.5% as reference (right).

Figure 5. Plot of RR by daily mean temperature at specific lags (left), RR by lag at specific daily mean temperature (right) in Jinan.

Reference at 15°C daily mean temperature.

Figure 6. Plot of RR by relative humidity at specific lags (left), RR by lag at specific daily relative humidity (right) in Jinan.

Reference at 58% of relative humidity.