Age of asthma onset and related risk factors for severity
Date Issued
2016
Date
2016
Author(s)
Wu, Tsung-Ju
Abstract
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.
Subjects
Adult asthma
asthma incidence
asthma severity
risk factors of asthma
air pollution
Type
thesis
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