SECULAR TREND IN THE OCCURRENCE OF ASTHMA AMONG CHILDREN AND YOUNG-ADULTS - CRITICAL-APPRAISAL OF REPEATED CROSS-SECTIONAL SURVEYS

Objectives: To review repeated surveys of the rising prevalence of obs tructive lung disease among children and young adults and determine wh ether systematic biases may explain the observed trends. Design: Revie w of published reports of repeated cross sectional surveys of asthma a nd wheezing among children and young adults. The repeated surveys used the same sampling frame, the same definition of outcome variables, an d equivalent data collection methods. Setting Repeated surveys conduct ed anywhere in the world. Subjects: All repeated surveys whose last se t of results were published in 1983 or later. Main outcome measures: L ifetime and current prevalences of asthma and current prevalence of wh eezing. The absolute increase (yearly percentage) in the prevalences o f asthma and wheezing was calculated and compared between studies. Res ults: 16 repeated surveys fulfilled the inclusion criteria. 12 reporte d increases in the current prevalence of asthma (from 0.09% to 0.97% a year) and eight reported increases in the current prevalence of wheez ing (from 0.14% to 1.24% a year). Changes in labelling are likely to h ave occurred for the reporting of asthma, and information biases may h ave occurred for the reporting of wheezing. Only one study reported an increase in an objective measurement Conclusions: The evidence for in creased prevalences of asthma and wheezing is weak because the measure s used are susceptible to systematic errors. Until repeated surveys in corporating more objective data are available no firm conclusions abou t increases in obstructive lung disease among children and young adult s can be drawn.