Prevalence of bronchial hyperresponsiveness and asthma in the adult population in Thailand.
OBJECTIVE
We conducted a nationwide cross-sectional survey of respiratory health in adults aged 20 to 44 years during 2001 to 2002 to determine the prevalence of bronchial hyperresponsiveness (BHR) and asthma in the adult Thai population.


METHODS
Subjects were selected by a multistage stratified random sampling. The stratification was done on geographic area, age group, and sex. Subjects were interviewed with questionnaires and underwent spirometric testing. Methacholine challenge tests were performed on all subjects without contraindication to determine BHR defined as the provocative concentration of methacholine producing a 20% fall in FEV(1) < or = 8 mg/mL. Definite asthma was defined as BHR present with any asthma symptom within the past 12 months or demonstrated reversible airflow obstruction. Current diagnosed asthma was defined as previous physician-diagnosed asthma and any asthma symptom within the past 12 months or currently receiving asthma medication.


RESULTS
The study population was from 20 provinces of five geographic regions of Thailand and included 1,882 women and 1,572 men. The prevalence of BHR was 3.31% (95% confidence interval [CI], 2.68 to 3.94). However, if subjects with positive reversibility test results were included, the prevalence increased to 3.98% (95% CI, 3.30 to 4.67). The prevalence of definite asthma was 2.91% (95% CI, 2.32 to 3.50), whereas the prevalence of current diagnosed asthma by the questionnaire interview was 2.15% (95% CI, 1.66 to 2.63). The kappa index of the agreement between both definitions of asthma was 0.40, indicating poor to fair agreement.


CONCLUSIONS
The prevalence of BHR and asthma in the adult Thai population is relatively low as compared with western countries.
Division of Respiratory Disease and Tuberculosis, Department of Medicine, Faculty of Medicine, Siriraj Hospital, 2 Prannok Road, Bangkoknoi, Bangkok 10700, Thailand. siwds@mahidol.ac.th
Wanchai
W
Dejsomritrutai
Arth
A
Nana
Nitipatana
N
Chierakul
Jamsak
J
Tscheikuna
Suree
S
Sompradeekul
Pimon
P
Ruttanaumpawan
Suchai
S
Charoenratanakul
D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000453:epidemiology*; D001985:Bronchial Provocation Tests; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D012135:Respiratory Sounds; D013147:Spirometry; D013785:Thailand / Q000453:epidemiology