Asthma incidence, remission, relapse and persistence: a population-based study in southern Taiwan.
BACKGROUND
In western countries, late-onset asthmatics are more severe than early-onset asthmatics in clinic-based studies. However, whether asthma occurrence rates were higher in late ages than in younger ages was inconclusive. This information is essentially lacking in Asian population.


METHODS
The participants were schoolchildren's parents recruited from 94 elementary and middle schools in 2004. A cross-sectional self-administered questionnaire was sent through the children to their parents to survey their respiratory health. We investigated typical asthma symptoms occurring at different ages and subsequent remission or relapse after the first asthma event. Person-years of the participants from birth to the time of survey were used as the denominator.


RESULTS
Among the 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.


CONCLUSIONS
In Asian population, asthma occurrence showed a U-shape age distribution with a prominent second peak in the thirties. A high proportion of early-onset asthma relapsed and most of late-onset asthma persisted or relapsed in adulthood.
Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, Taipei, Taiwan. docdocwu@gmail.com.|Division of Chest Medicine, Department of Internal Medicine, Kaohsiung Municipal Min-Sheng Hospital, Kaohsiung, Taiwan. docdocwu@gmail.com.
Tsung-Ju
TJ
Wu
Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, Taipei, Taiwan. changfu@ntu.edu.tw.
Chang-Fu
CF
Wu
Institute of Epidemiology and Preventive Medicine, National Taiwan University, Taipei, Taiwan. leolee@ntu.edu.tw.
Yungling Leo
YL
Lee
Division of Chest Medicine, Department of Internal Medicine, National Cheng Kung University Hospital, Medical College, National Cheng Kung University, Tainan, Taiwan. hsiue@mail.ncku.edu.tw.
Tzuen-Ren
TR
Hsiue
Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University, Taipei, 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.
Yue Leon
YL
Guo
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D044466:Asian People; D001249:Asthma / Q000175:diagnosis / Q000208:ethnology* / Q000628:therapy; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012008:Recurrence; D012074:Remission Induction; D012307:Risk Factors; D017678:Sex Distribution; D012737:Sex Factors; D011795:Surveys and Questionnaires; D013624:Taiwan / Q000453:epidemiology; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult