氣喘發生年齡及相關嚴重度危險因子

Abstract

氣喘病的發生年齡是疾病的重要表現型。到目前為止，在台灣並沒有針對氣喘年齡別發生率、發生年齡相關的嚴重度及危險因子的報告，因此藉由台灣氣喘年齡別發生率、發生年齡相關的嚴重度及危險因子的分析，作為介入預防之憑據。 本研究之整體目標為： 一、探討在南台灣年齡別氣喘發生率是否有U型分佈；是否如同歐美國家一樣在青春期前後有性別差異；氣喘的發生年齡是否與目前氣喘的活動性（復發或持續性氣喘）有關； 二、探討在成人時期發生的氣喘(遲發型氣喘)是否比兒童時期發生的氣喘(早發型氣喘)嚴重；成人時期發生的氣喘與兒童時期發生的氣喘是否有不同的危險因子； 三、探討在成人時期慢性暴露大氣中空氣污染物對成人時期發生的氣喘造成的影響是否比兒童時期發生的氣喘嚴重； 本研究使用之資料為2004年在南台灣的學童及家長呼吸系統健康問卷調查，問卷總共評估了35,682位學童的父母。成人氣喘的問卷為中文版的美國胸腔學會ATS-DLD-78問卷。嚴重度的評估則參考GINA、NHLBI、ATS等學會或機構的建議，選取氣喘症狀發生頻率、氣喘緊急用藥頻率、控制用藥頻率、急診或住院就醫頻率做為指標，空氣污染的暴露則採用kriging方法做為個人暴露值的推估。 第一個研究25,377位參與分析，其中發現886位氣喘患者，發生年齡41歲以上者26位不列入分析，共有860位。在25,377位參與分析者，從出生至問卷分析時總人年為949,807。粗發生率女性高於男性。最高發生率在0-12歲及36-40歲。年齡別發生率介於每千人年0.45人(19-25歲)至2.03人(36-40歲)，而年輕族群者粗發生率有上升趨勢。男性在15歲以前易發生氣喘，女性在16歲以後易發生氣喘。年齡別發生率以出生年齡調整後的雙峰模式不變，但第二高峰更明顯。不同氣喘年齡層氣喘痊癒的比率類似，持續性氣喘的比率則在遲發性氣喘(>12歲)較高；而復發的比率則以早發型(≦12歲)的較高。總數而言，遲發型的氣喘有較高的活動性。在仍有活動性的氣喘中，仍有類似的雙峰模式。第二個研究分析曾經醫師診斷為氣喘病者共449人。發生年齡在13-50歲者較發生年齡在12歲及以下者有較高使用氣喘緊急用藥(SABA)、控制用藥(ICS)和急診或住院就醫的風險。以發生年齡12歲分層分析兩組，過敏性鼻炎在SABA及ICS模式是早發型氣喘嚴重度的危險因子，而除濕設備的使用在SABA及ICS模式是遲發型氣喘嚴重度的保護因子。第三個研究分析典型氣喘病症狀者共703人。以發生年齡12歲分層分析兩組，以氣喘嚴重度組合分數為嚴重度指標，發現大氣中PM10是遲發型氣喘的嚴重度危險因子，但不是早發型氣喘的嚴重度危險因子。 綜上所論，在南臺灣氣喘發生率在30-40歲有第二高峰，而其嚴重度較早發型氣喘為嚴重，在台灣全島是否有相同的趨勢及造成遲發型氣喘的致病因子需要進一步研究，以遏止此一增加的趨勢。在減低成人時期遲發型氣喘的嚴重度方面，減低大氣懸浮微粒及除濕設備的使用為重要措施，而其致病機轉也有待進一步研究。

Age of asthma onset is an important phenotype and characteristic in asthma outcomes. Up to date, there has been no report on incidence rates of asthma by age group in Taiwan and relative severity and risk factors by age of asthma onset. Understanding of the information will benefit in a targeted management plan for asthma. In order to propose comprehensive intervention of asthma, we would like to investigate incidence rates of asthma onset by age group and analysis age-specific severity and risk factors. The aims of this study are: to examine whether there is a U-shape pattern of age-specific incidence of asthma in southern Taiwan; whether the sex difference in asthma incidence is similar with western countries; whether the onset age of asthma is related with active asthma (persistence or relapse) in adulthood; to examine whether in a population-based study, adult-onset asthma is more severe than childhood-onset asthma; whether the risk factors for asthma severity are different between adult-onset asthma and childhood-onset asthma; to examine whether air pollution is a risk factor for the severity of adult-onset asthma. The study utilized the data obtained from a cross-sectional school-based survey for respiratory diseases and symptoms for schoolchildren’s parents in southern Taiwan between March and October 2004. The questionnaire for parents’ respiratory health was a Chinese version modified from the questionnaire of the American Thoracic Society and the Division of Lung Diseases (ATS-DLD-78). The outcome measurement was asthma severity defined by frequency of asthma symptoms, short-acting β2-agonist, inhaled corticosteroid and health care use, i.e., emergency department visits or hospitalizations in the past 12 months. These severity measures were recommended by Global Initiative for asthma (GINA), National Heart, Lung, and Blood Institute (NHLBI), and American Thoracic Society (ATS), etc. Personal exposure to air pollution will be estimated by air monitoring station data and kriging method. The thesis is composed of three studies. In the first study, among 25,377 participants consisting of 949,807 total person-years, 860 reported ever having asthma. Highest incidences occurred at ages 0-12 and 36-40 years. The incidence of asthma was higher in males before puberty, and higher in females after puberty, with overall incidences 1.00 and 0.77 per 1000 person-years for females and males, respectively. Participants with late-onset asthma (onset age > 12 years) comprised a large portion of adult current asthmatics. More than 52% of persistence or relapse was observed in early-onset asthma (onset age ≤ 12 years). The younger birth cohort had a more prominent later peak of asthma incidence than the older one. In the second, 449 physician-diagnosed asthmatics were eligible for analysis. The risks of rescue SABA, ICS and healthcare use were generally higher among late-onset (13-50 years) than early-onset (0-12 years) asthmatics. Use of SABA and healthcare increased from childhood-onset, adolescent- or young adult-onset to adult-onset asthma. Allergic rhinitis was positively associated with SABA use (OR, 9.08; 95% CI, 1.06-77.99) and ICS use (OR, 5.08; 95% CI, 1.47-17.52) in early-onset asthma. Dehumidifier use was negatively associated with SABA use (OR, 0.50; 95% CI, 0.29-0.87) and ICS use (OR, 0.38; 95% CI, 0.19-0.78) in late-onset asthma. In the third study, 703 questionnaire-determined asthmatics were identified and included for analysis. Using the median of PM10 (66 μg/m3) as a cut-off, those exposed to higher PM10 were more likely to have higher severity scores (OR = 1.74; 95% CI, 1.13 – 2.70) only for asthmatics with asthma onset at > 12 years. In conclusion, a U-shape age distribution of asthma onset with a prominent second peak in the thirties in southern Taiwan. Late-onset asthma was more severe than early-onset asthma in adulthood. Whether there is a similar trend in whole Taiwan and the causing factor of late-onset asthma deserve further studies to initiate an intervention. On the other hand, the decrease of ambient PM10 and use of dehumidifier are important measures to reduce the severity of late-onset asthma. In addition, the underlying pathogenesis warrants further studies.