Rationale for ISAAC

At the time that ISAAC was conceived, in the early 1990s, most previous research had looked at the reasons why some individuals rather than others develop asthma and allergic conditions such as allergic rhinitis and eczema. A major risk factor was a family history of atopic disease, but various environmental factors had been also considered important in the expression of disease. Such studies within populations had shed little light on the reasons why the occurrence of atopic disease varies from population to population.

Factors affecting the prevalence of disease at a population level may be different to those that determine which individuals within a population were at greatest risk. In addition, between populations the relationship between the three atopic conditions may be different. It was therefore considered likely that “ecological” (between-population) analyses might reveal further important determinants of asthma, allergic rhinitis and eczema. There was also widespread concern that these conditions were increasing in both developed and developing countries, but there was a lack of information on the burden of allergic diseases in many parts of the world.

One obstacle to the investigation of population differences (and of trends) had been the lack of a suitable and generally accepted method of measuring the prevalence and severity of asthma and other atopic diseases in children which could be used worldwide. Another obstacle was the absence of a coordinated research programme to obtain and analyse comparative data. The International Study of Asthma and Allergies in Childhood (ISAAC) programme was developed in 1991 to address these issues.