扇風機で酷暑が健康に及ぼす悪影響を低減する
Abstract
Background
Heatwaves are hot weather events, which breach regional or national thresholds, that last for several days. They are likely to occur with increasing frequency in some parts of the world. The potential consequences were illustrated in Europe in August 2003 when there were an estimated 30,000 excess deaths due to a heatwave. Electric fans might be used with the intention of reducing the adverse health effects of a heatwave. Fans do not cool the ambient air but can be used to draw in cooler air from outside when placed at an open window. The aim of the fans would be to increase heat loss by increasing the efficiency of all normal methods of heat loss, but particularly by evaporation and convection methods. However, it should be noted that increased sweating can lead to dehydration and electrolyte imbalances if these fluids and electrolytes are not replaced quickly enough. Research has also identified important gaps in knowledge about the use of fans, which might lead to their inappropriate use.
Objectives
To determine whether the use of electric fans contributes to, or impedes, heat loss at high ambient temperatures during a heatwave, and to contribute to the evidence base for the public health impacts of heatwaves.
Search methods
We sought unpublished and published studies that had been published in any language. The review team were able to assess studies reported in English, Chinese, Dutch, French and German; and reports in other languages would have been translated into English as necessary. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, the Indian biomedical literature (IndMED and MedIND) and databases of Chinese literature (Chinese Journal Net and Digital Periodical of WanFang Data). The most recent electronic searches were done in April 2012. We also checked the reference lists of relevant articles and the websites of relevant national and international organisations, and consulted with researchers and policy makers with experience in strategies to manage heatwaves to identify additional studies. The titles and abstracts from each search were checked independently by two review authors. The full text articles that we retrieved were checked independently by at least two authors for their relevance and for references to potentially eligible studies.
Selection criteria
Randomised trials and other experimental designs, such as interrupted time series and controlled before‐and‐after studies, comparing the use of electric fans with no fans during a heatwave were eligible for this review. The electric fans could be hand‐held (battery operated), portable or mounted on the wall or ceiling, or in a window. We sought interventions delivered to anyone for whom a heatwave was likely to have serious adverse health impacts. This would include people of all ages but with a particular focus on some groups (for example older people). Populations from high‐, middle‐ and low‐income countries were eligible for the review.
Data collection and analysis
If we had identified eligible studies, they would have been assessed independently by at least two review authors and data would have been extracted on the characteristics of the study, its participants and interventions, as well as the effects on health outcomes. The primary outcomes were mortality, hospital admission and other contacts with healthcare services.
Main results
We did not identify any eligible studies despite the extensive searching and correspondence with several experts in this topic area. We identified retrospective, observational studies, usually with a case‐control design, that investigated the association between the use of electric fans and health outcomes, including death. The results of these studies were mixed. Some studies found that the use of fans was associated with better health outcomes, others found the reverse.
Authors' conclusions
The evidence we identified does not resolve uncertainties about the health effects of electric fans during heatwaves. Therefore, this review does not support or refute the use of electric fans during a heatwave. People making decisions about electric fans should consider the current state of the evidence base, and they might also wish to make themselves aware of local policy or guidelines when making a choice about whether or not to use or supply electric fans. The main implication of this review is that high quality research is needed to resolve the long standing and ongoing uncertainty about the benefits and harms of using electric fans during a heatwave, for example randomised trials comparing the health effects in people with electric fans to those in people without them.
PICO
Plain language summary
扇風機で酷暑が健康に及ぼす影響を低減する
酷暑は珍しくなくなってきており、その影響はとてもひどいことがある。例えば、2003年8月のヨーロッパでは、酷暑のために30,000人が死亡した可能性がある。扇風機は暑さから逃れるための手段の１つだが、これが良いか悪いかは確かでない。35度以下かつ扇風機が直接人に向いていなければ、扇風機は熱損失を増大させる（訳注：熱を奪う）可能性がある。しかし、35度以上であれば熱利得に寄与する（訳注：熱を与える）可能性がある。また、過度の発汗は脱水やその他の健康問題につながる可能性がある。したがって、扇風機を使うか否かを決めるためには、利益と害について知ることが重要である。これは扇風機の使用について、個人的な決定にも影響するが、酷暑の際に人々の集団に扇風機を与えるべきか否かなどの、より広い公衆衛生上の決定についても関与している。このことは、高齢者などの発汗したり皮膚への血液の流れを増やしたりして身体を冷やすことが難しい、熱の影響を受けやすいと考えられる人々にとって特に重要である。
このコクランレビューはディシジョンメーカーを助けるであろういくつかの答えを提供しようとしたものである。酷暑の間に扇風機を使用したグループと使用しなかったグループを比較した質の高い研究を探したが、要件を満たす研究は見つからなかった。この問いに答えるのに信頼性の低いデザインがされたいくつかの研究が見つかり、これらの結果はさまざまであった。扇風機が健康問題を減らすとしたものもあり、一方で扇風機が事態を悪くするとしたものもあった。
したがって、これまでに行われた研究は酷暑における扇風機の影響について解き明かすものではなかった。意思決定者は、ローカルな指針やガイドラインと共に現時点のエビデンスを考慮すべきである。酷暑の際に扇風機を使用することの利益と害を、確かなエビデンスをもって決定づけられるような質の高い研究が求められる。
