Age of asthma onset and vulnerability to ambient air pollution: an observational population-based study of adults from Southern Taiwan.
BACKGROUND
Late-onset asthma (onset > 12 years) is pathologically distinct from early-onset asthma. The mechanism of air pollution is not a classic allergic inflammation and could have differential effect on late-onset and early-onset asthma. However, there is little known about the association of onset-age phenotype and air pollution. In this population-based study, we aimed to determine the association of asthma severity outcomes and air pollution regarding age at onset of asthma.


METHODS
In 2004, we conducted a cross-sectional questionnaire survey about respiratory health among schoolchildren's parents randomly selected from 94 of 816 elementary and middle schools in southern Taiwan. Participants ever having typical asthma symptoms were enrolled. We used kriging method to estimate individual exposure to ambient air pollution in the preceding year before the year of asthma severity survey. Ordered logistic regression was used to determine the association of exposure and asthma severity scores. Age at asthma onset of 12 years was used as a cut-off to define early- or late-onset asthma.


RESULTS
The study surveyed 35,682 participants. Data from 23,551 participants remained satisfactory with a response rate of 66 %. Among 20,508 participants aged 26-50 years, 703 questionnaire-determined asthmatics were identified and included for analysis. Using the median of PM10 (66 μg/m(3)) 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.


CONCLUSIONS
In adulthood, exposure to PM10 has a greater effect on late-onset asthma than early-onset asthma and deserves greater attention among ambient air pollutants.
Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, 17, Syujhou Road, Taipei, 100, Taiwan.|Division of Chest Medicine, Department of Internal Medicine, Kaohsiung Municipal Min-Sheng Hospital, Kaohsiung, Taiwan.
Tsung-Ju
TJ
Wu
Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, 17, Syujhou Road, Taipei, 100, Taiwan.
Chang-Fu
CF
Wu
Department of Environmental and Occupational Medicine, National Taiwan University (NTU) College of Medicine and NTU Hospital, Taipei, Taiwan.
Bing-Yu
BY
Chen
Institute of Epidemiology and Preventive Medicine, National Taiwan University, 17, Syujhou Road, Taipei, 100, Taiwan.
Yungling Leo
YL
Lee
Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, 17, Syujhou Road, Taipei, 100, Taiwan. leonguo@ntu.edu.tw.|Department of Environmental and Occupational Medicine, National Taiwan University (NTU) College of Medicine and NTU Hospital, Taipei, Taiwan. leonguo@ntu.edu.tw.|National Institute of Environmental Health Sciences, National Health Research Institutes, Zhunan, Taiwan. leonguo@ntu.edu.tw.
Yue Leon
YL
Guo
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000397:Air Pollution / Q000009:adverse effects*; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D052638:Particulate Matter / Q000009:adverse effects*; D011159:Population Surveillance; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013624:Taiwan / Q000453:epidemiology; D055815:Young Adult
D052638:Particulate Matter
Adult asthma; Air pollution; Particulate matter; Phenotype