Evidence for the increase in asthma worldwide

Area of Science:

• Epidemiology
• Environmental Health
• Allergology

Background:

• Asthma prevalence is increasing worldwide, especially in children and adolescents.
• Wheezing illness prevalence has risen in countries with consistent epidemiological studies over the past 20 years.
• Significant global variations in asthma prevalence persist, with high rates in Australasia and low rates in developing countries.

Purpose of the Study:

• To review evidence on the increasing prevalence of asthma.
• To explore the role of environmental risk factors in the rise of asthma.
• To examine trends in asthma prevalence and associated risk factors.

Main Methods:

• Review of epidemiological studies using questionnaire definitions like 'asthma ever diagnosed' and 'wheeze ever'.
• Analysis of serial studies conducted over the last 20 years in various countries.
• Examination of risk factors including atopy, parental asthma, allergen exposure, infections, diet, and socioeconomic factors.

Main Results:

• Consistent increases in wheezing illness in children and adolescents have been recorded globally.
• Data is insufficient to confirm increasing asthma trends in adults.
• Key risk factors for childhood asthma include atopy, parental history, allergen load, infections, diet, and affluence.

Conclusions:

• The global increase in asthma is likely multifactorial, driven by combined lifestyle changes affecting immunological protection and allergen exposure.
• Changes in environmental risk factors, such as indoor allergen levels, diet, and infections, are suggested but evidence is indirect.
• While atopy prevalence may be increasing, it's possibly due to earlier acquisition, not necessarily a rise in the underlying predisposition.