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What have we learnt from studies on the association between urbanisation and asthma prevalence?
  1. William Checkley
  1. Division of Pulmonary and Critical Care, Johns Hopkins University, Baltimore, Maryland, USA
  1. Correspondence to Dr William Checkley, Division of Pulmonary and Critical Care, Johns Hopkins University, Baltimore, MD 21287, USA; wcheckl1{at}

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The world’s urban population is growing rapidly. In 1950, only 751 million individuals resided in urban areas whereas by 2018 this had increased to 4.2 billion, with 828 million estimated to be living in urban slums.1 2 Current projections show that urbanisation could add 2.5 billion people to urban settings by 2050, a figure which translates to approximately two-thirds of the global population.1 The pace of urbanisation presents important challenges to development for many cities in Africa, Asia and Latin America, where much of this expansion is unplanned or poorly planned, and exacerbates socioeconomic disparities and unsanitary conditions.3 Slum environments bear the largest burden of inadequate urban infrastructure, which in turn results in a confluence of distal and proximal causes of human disease. A better understanding of risk factors related to urbanisation can help to prevent or treat common chronic diseases like asthma.

Multiple studies have linked asthma outcomes to increased urbanisation. Approximately 14% of children worldwide experience asthma symptoms each year, making it the most common chronic disease in childhood.4 In this issue of Thorax, Rodriguez et al 5 conducted a systematic review and meta-analysis of epidemiological …

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  • Contributors WC was responsible for writing the editorial.

  • Funding William Checkley is funded by the United States National Institutes of Health (U01TW010107, U2RTW010114, UM1HL134590, D43TW009340).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Commissioned; externally peer reviewed.

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