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作者：Laurie Barclay, MD  
出處：WebMD醫學新聞

　　September 17, 2009 — 根據發表於9月過敏、氣喘與免疫學年報(Annals of Allergy, Asthma Immunology)上一篇為期兩年的回溯研究結果，氣候改變與孩童之氣喘惡化有關。
　　
　　第一作者、曾任職於底特律韋恩州立大學醫學院、密西根兒童醫院，現執業於德州Dallas Allergy Immunology的過敏專家Nana A. Mireku醫師在新聞稿中表示，最新的國家健康研究中心指引，列出氣候改變是氣喘的可能預測因子，但是之前並無研究以嚴謹方法實際檢視這個可能因子。
　　
　　Mireku醫師表示，就我們所知，這是首次控制空氣污染物與一般空氣過敏原之後，提出這些關聯的研究。我們的研究也是少數檢視氣候的研究之一，探討在氣喘惡化前每天或每兩天與住院當天氣候改變之影響程度、以及氣候變化之後一、兩天造成急診的情況。
　　
　　研究目標是評估氣溫、溼度、大氣壓力等氣候因素的變動對於孩童氣喘惡化的影響。從2004年1月1日至2005年12月31日，將因氣喘而前往一個大型都會醫院急診的孩童納為研究對象。
　　
　　研究者蒐集每天的氣候因素、污染物與空氣過敏原的資料。藉由時間序列分析，控制季節性、空物污染、空氣過敏原曝露等因素，他們確認每天或每兩天的氣候因素改變與氣喘急診就醫的關係。分析25,401例氣喘急診，住院當天(T = 0)以及住院前至多5天(T - 5 到T - 1)的氣候因素影響。
　　
　　在T -1或T- 2時，每天溼度每增加10%，即與增加1例氣喘就醫有關(P值分別是P < .001與P = .01)。從T -3到T -2的每兩天溼度變化也與較多急診就醫有關(P < .001)，T -1到T = 0的每兩天溫度改變也有關。T -1到T = 0時氣溫每增加10°F(約增加5.5℃)，與增加1.8例氣喘就醫有關(P =.006)。大氣壓力的改變並未對急診就醫有所影響。
　　
　　Mireku醫師表示，我們發現氣溫和溼度變動與小兒氣喘惡化之間有強烈關聯，而大氣壓力則無關。
　　
　　研究限制包括受限於回溯研究，氣喘案例可能錯誤分類、無法控制病毒感染因素。
　　
　　過敏專家、美國過敏氣喘暨免疫協會總裁Richard G. Gower醫師在一篇聲明中表示，氣喘是孩童最常見的慢性疾病。長久以來，過敏專家都知道過度乾燥、潮濕或刮風等氣候因素會影響氣喘症狀。本研究進一步確認了氣溫與溼度對於孩童氣喘的影響角色，也確認了瞭解病患症狀發生來源的重要性，這有助於擬定適合他們的治療計畫。
　　
　　研究作者皆宣告沒有相關資金上的往來。

Changes in Weather Linked to Asthma Exacerbations in Children

By Laurie Barclay, MD
Medscape Medical News

September 17, 2009 — Changes in weather are linked to asthma exacerbations in children, according to the results of a 2-year, retrospective study reported in the September issue of the Annals of Allergy, Asthma Immunology.

"The latest National Institutes of Health guidelines list 'change in weather' as a possible precipitating factor for asthma, but no previous studies have really examined this potential trigger in a rigorous fashion," lead author Nana A. Mireku, MD, an allergist at Dallas Allergy Immunology private practice in Texas, formerly at Children's Hospital of Michigan, Wayne State University School of Medicine, Detroit, said in a news release.

"To our knowledge, this is the first study that demonstrated these correlations after controlling for levels of airborne pollutants and common aeroallergens," Dr. Mireku said. "Our study is also one of the few to examine the possibility that the weather one or two days before the asthma exacerbation may be as important as that on the day of admission, as the additional [emergency department (ED)] visits occur one to two days after the fluctuation."

The goal of this study was to evaluate the effect of fluctuations in climatic factors, including temperature, humidity, and barometric pressure, on asthma exacerbations in children. From January 1, 2004, to December 31, 2005, children seen for an asthma exacerbation at the ED of a large urban hospital were included in the study sample.

The investigators collected daily data on climactic factors, pollutants, and aeroallergens. Using time series analysis, they determined the relationship of daily (intraday) or between-day (interday) changes in climactic factors and asthma ED visits, controlling for seasonality, air pollution, and aeroallergen exposure. The effects of climactic factors were assessed on the day of admission (T = 0) and up to 5 days before admission (T ? 5 through T ? 1) for 25,401 asthma ED visits.

On day T ? 1 or day T ? 2, a 10% intraday increase in humidity was associated with approximately 1 additional ED visit for asthma (P < .001 and P = .01, respectively). Interday changes in humidity from day T ? 3 to T ? 2 were also linked to more ED visits (P < .001), as were interday changes in temperature from T ? 1 to T = 0. A 10°F increase from T ? 1 to T = 0 was associated with 1.8 additional visits (P = .006). Changes in barometric pressure did not appear to affect ED visits.

"We found a strong relationship between temperature and humidity fluctuations with pediatric asthma exacerbations, but not barometric pressure," Dr. Mireku said.

Limitations of this study include those inherent in a retrospective study, such as possible misclassification of asthma cases and inability to control for viral infections.

"Asthma is the most common chronic illness in childhood," said allergist Richard G. Gower, MD, president of the American College of Allergy, Asthma and Immunology, in a statement. "Allergists have long known that weather conditions such as extremely dry, wet, or windy weather can affect asthma symptoms. This study further defines the role of temperature and humidity on children's asthma and confirms the importance of working with patients to identify the source of their symptoms and develop treatment plans that help prevent them."

The study authors have disclosed no relevant financial relationships.

Ann Allergy Asthma Immunol. 2009;103:220–224.