Problems of measuring asthma prevalence

Abstract

This review considers the issues involved in measuring the community prevalence of asthma, particularly in the context of international comparisons. We argue that there is no gold standard definition for measuring asthma prevalence, and discuss the currently available methods of case ascertainment. Prevalence studies, if they are to be generalizable, need to involve large sample sizes with high response rates. This necessitates methods that are simple, inexpensive and practicable, but also as sensitive and specific for asthma as possible. We discuss some of the issues that are specific to comparisons of asthma prevalence between diverse populations, and suggest that large surveys using written or video questionnaires of self reported symptoms validated in all of the target populations are the method of choice.Key words: asthma, bronchial hyperreactivity, epidemiology, prevalence, questionnaires.It could be argued that asthma epidemiology is at the stage cancer epidemiology was 30 years ago, when an international study compared cancer incidence across the continents of the world.' The striking differences in incidence that were found in this study gave rise to a number of hypotheses about possible causes of the international patterns, some of which were subsequently confirmed. Hundreds of asthma prevalence studies have been carried out in numerous parts of the world but international comparisons between countries have for the most part been impossible because the studies have not used common methods, or common definitions of asthma. In order to investigate the underlying causes of asthma, international comparisons of prevalence analogous to those previously conducted for cancer incidence are vital, and are now underway. There have so far been a very small number of studies that have used common protocols to compare prevalence between ~ountries.2,~

Urban–rural differences in asthma prevalence among young people in Canada: the roles of health behaviors and obesity

“…This method has reasonable levels of agreement with other methods of assessment and indeed has been considered the method of choice for large epidemiologic studies. 36 Adolescent reports on respiratory symptoms have been found to be accurately reported by the child and strongly agree with parental reports in terms of asthma diagnoses. 37 Despite this, asthma prevalence could be overdiagnosed in this population given the high asthma prevalence and the self-reported nature of the original data source.…”

Childhood asthma, asthma severity indicators, and related conditions along an urban-rural gradient: a cross-sectional study

“…This can result in potential recall bias. Despite this, survey responses regarding asthma have been shown to be relatively accurate and are often the methods of choice in large epidemiological studies due to practical constraints such as cost and efficiency [35]. A limitation of our study could be that we collected data in spring when outdoor allergens and seasonal allergies are most common which could results in asthma symptoms.…”

Airway resistance and atopy in preschool children with wheeze and cough

“…Reported wheeze remains the cornerstone of the epidemiological assessment of asthma [23,24]. Because of the concern that there is reporting bias of respiratory symptoms such as wheeze [25] and uncertainty as to whether persistent cough should be considered asthma [12], the need for objective testing for asthma in preschool children as well as school children is compelling [33].…”