Assessing the Short-Term Effects of Heatwaves on Mortality and Morbidity in Brisbane, Australia: Comparison of Case-Crossover and Time Series Analyses

BackgroundHeat-related impacts may have greater public health implications as climate change continues. It is important to appropriately characterize the relationship between heatwave and health outcomes. However, it is unclear whether a case-crossover design can be effectively used to assess the event- or episode-related health effects. This study examined the association between exposure to heatwaves and mortality and emergency hospital admissions (EHAs) from non-external causes in Brisbane, Australia, using both case-crossover and time series analyses approaches.
MethodsPoisson generalised additive model (GAM) and time-stratified case-crossover analyses were used to assess the short-term impact of heatwaves on mortality and EHAs. Heatwaves exhibited a significant impact on mortality and EHAs after adjusting for air pollution, day of the week, and season.
ResultsFor time-stratified case-crossover analysis, odds ratios of mortality and EHAs during heatwaves were 1.62 (95% confidence interval (CI): 1.36–1.94) and 1.22 (95% CI: 1.14–1.30) at lag 1, respectively. Time series GAM models gave similar results. Relative risks of mortality and EHAs ranged from 1.72 (95% CI: 1.40–2.11) to 1.81 (95% CI: 1.56–2.10) and from 1.14 (95% CI: 1.06–1.23) to 1.28 (95% CI: 1.21–1.36) at lag 1, respectively. The risk estimates gradually attenuated after the lag of one day for both case-crossover and time series analyses.
ConclusionsThe risk estimates from both case-crossover and time series models were consistent and comparable. This finding may have implications for future research on the assessment of event- or episode-related (e.g., heatwave) health effects.

研究背景
随着气候变化持续演进，高温相关健康事件对公共卫生的潜在影响或将进一步凸显。精准刻画热浪与健康结局之间的关联至关重要。然而，目前尚不清楚病例交叉设计（case-crossover design）能否被有效用于评估与事件或发作相关的健康效应。本研究以澳大利亚布里斯班为研究区域，采用病例交叉设计与时间序列分析两种方法，探究了热浪暴露与非外部原因导致的死亡及急诊住院（Emergency Hospital Admissions, EHAs）之间的关联。

研究方法
本研究采用泊松广义相加模型（Poisson generalised additive model, GAM）与时间分层病例交叉分析，评估热浪对死亡及急诊住院的短期影响。在校正空气污染、星期几效应及季节因素后，热浪对死亡及急诊住院存在显著影响。

研究结果
在时间分层病例交叉分析中，热浪期间死亡及急诊住院的比值比（odds ratio, OR）在滞后1天时分别为1.62（95%置信区间（confidence interval, CI）：1.36~1.94）与1.22（95% CI：1.14~1.30）。时间序列GAM模型得到了相似的结果：在滞后1天时，死亡及急诊住院的相对危险度（relative risk, RR）分别介于1.72（95% CI：1.40~2.11）至1.81（95% CI：1.56~2.10）以及1.14（95% CI：1.06~1.23）至1.28（95% CI：1.21~1.36）之间。无论是病例交叉分析还是时间序列分析，风险估计值在滞后1天后均逐渐衰减。

研究结论
两种分析方法得到的风险估计值具有一致性与可比性。该发现可为未来评估与事件或发作（如热浪）相关的健康效应的研究提供参考。