Elektrische Ventilatoren zur Verringerung nachteiliger Auswirkungen von Hitzewellen auf die Gesundheit
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We sought unpublished and published studies that had been published in any language.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
Elektrische Ventilatoren zur Verringerung der Auswirkungen von Hitzewellen auf die Gesundheit
Hitzewellen treten immer häufiger auf und ihre Auswirkungen können verheerend sein. Zum Beispiel kamen durch die Hitzewelle in Europa im August 2003 wahrscheinlich bis zu 30.000 Menschen ums Leben. Eine Möglichkeit, um die Auswirkungen von Hitze zu verringern, sind elektrische Ventilatoren. Jedoch ist noch nicht klar, ob diese mehr Nutzen oder Schaden bringen. Ein Ventilator kann bei Temperaturen unter 35 °C, und wenn er nicht direkt auf die Person gerichtet ist dabei helfen die Hitze zu mindern. Allerdings kann der Ventilator bei Temperaturen über 35 °C selbst zur Hitzeproduktion beitragen. Übermäßiges Schwitzen kann außerdem zu Dehydratation (Entwässerung) und anderen gesundheitlichen Problemen führen. In der Frage, ob ein elektrischer Ventilator verwendet werden sollte, ist es daher wichtig die potentiellen nützlichen und schädlichen Wirkungen von diesen Geräten zu kennen. Das betrifft den eigenen Gebrauch von Ventilatoren aber auch Entscheidungen in der öffentlichen Gesundheit, um zu bestimmen, ob es von Nutzen wäre elektrische Ventilatoren an bestimmte Gruppen von Menschen während Hitzewellen zu verteilen oder nicht. Dies ist besonders wichtig für Menschen, die anfälliger für Hitze sind, z.B. ältere Menschen, die in einem geringeren Maße fähig sind durch Schwitzen den eigenen Körper herabzukühlen, oder den Blutfluss hin zur Haut zu erhöhen.
Dieser Cochrane Review versuchte einige Antworten zu finden, die besonders relevant für Entscheidungsträger sind. Wir suchten nach Studien von hoher Qualität, die eine Gruppe an Menschen, die während Hitzewellen Ventilatoren verwendeten, mit einer Gruppe verglichen, die diese Geräte während Hitzewellen nicht nutzten. Wir fanden jedoch keine Studien, die diesen Anforderungen entsprachen. Wir fanden einige Studien, die Studiendesigns verwendeten, die für die Beantwortung dieser Art von Frage weniger zuverlässig sind. Diese Studien zeigten gemischte Ergebnisse. In einigen deutete sich an, dass Ventilatoren gesundheitliche Probleme verringern könnten, und in anderen schienen Ventilatoren diese Probleme eher zu verschlimmern.
Dadurch lässt sich sagen, dass die vorhandenen wissenschaftlichen Erkenntnisse die Unklarheiten bezüglich der gesundheitlichen Auswirkungen von elektrischen Ventilatoren und deren Benutzung während Hitzewellen nicht lösen. Entscheidungsträger sollten die aktuelle Evidenz und die örtlichen Vorschriften und Richtlinien berücksichtigen. Sie können zusätzlich zur Klärung der Ungewissheit beitragen indem sie jene Art von qualitativ hochwertiger Forschung betreiben, die zuverlässige Evidenz liefern würde, um feststellen zu können, ob die Benutzung von elektrischen Ventilatoren während Hitzewellen einen Nutzen oder Schaden mit sich bringt.
