天氣與自殺: 一東台灣病例對照研究

Abstract

背景：天氣與自殺的關係早已受到關注，以往的研究多採用生態研究方法，雖然考慮到諸多的干擾因素之控制，其結果多不一致，而迄今尚未有相關研究採用個案對照的方法。 目的：以東台灣三個種族的自殺研究樣本與資料為基礎，探討天氣變項與自殺之間的關係。 方法：研究採用生態研究法 (Poisson regression model)與病例對照法 (conditional regression model)，前者探討逐日天氣變項與當日自殺事件之間的關係; 後者探討自殺組與對照組的天氣暴露狀態有無不同。同時也分析暴力型自殺與非暴力型自殺，以及若干不同個體特質族群的自殺是否受天氣影響的程度不同。 結果：生態研究發現溫度的增加僅在女性自殺樣本有意義地提高自殺的危險性 (p=0.049)，病例對照研究發現整體自殺組的平均溼度暴露顯著地高於對照組(風險比1.064，p=0.0012)，此種顯著相關性同時存在於非暴力型自殺、男性、女性、非老年的自殺族群，但不存在於暴力型自殺與老年的自殺族群。天氣與自殺的關係在調整了物質依賴、失落經驗、情緒不穩性人格障礙、自殺行為家族史等個人變項的效應之後仍然存在。 結論：本研究顯示平均溼度的增加提高易感者的自殺風險，非暴力型自殺受天氣因素的影響大於暴力型自殺，天氣對於自殺方法的選擇及其背後的機轉之影響可能不同。

Background: Studies investigating the relationship between weather and suicide were mostly conducted by ecological study design with equivocal results. No study has been conducted with a case-control design. Aims: To examine the associations between weather and suicide in three ethnic groups in East Taiwan. Method: Poisson regression analysis and conditional logistic regression analysis were conducted separately. The former, based on ecological study design, investigated the association between daily suicide count and daily weather parameters. The latter, based on case-control study design, investigated the difference in weather exposure between suicides and controls. Effects of weather on suicide risk were also investigated against methods of suicide (violent and non-violent) and personal characteristics. Result: In Poisson regression model, elevated high temperature significantly increased suicide risk in female (p=0.049). In conditional logistic regression model, elevated mean humidity significantly increased suicide risk in all suicides (Odds Ratio 1.064, p=0.0012); in non-violent suicides, in both sexes and in non-elderly suicides, but not in violent and elderly suicides. The significant association between weather and suicide has remained after adjusting for the effect of substance dependent, emotionally unstable personality disorder, loss event and family history of suicidal behavior. Conclusions: Elevated humidity significantly increased suicide risk in susceptible individuals. The effect of short-term weather condition on suicide is more significant in non-violent suicides. The influence of weather on suicide and its underlying mechanisms may differ with different methods of suicide.