Trends in asthma diagnosis in children in East London general practices

Problem

Asthma is a common chronic respiratory condition affecting 10% of the UK population. Association between exacerbation of asthma and exposure to traffic related pollution has been previously identified. We sought to determine the incidence of new childhood asthma diagnosis in East London over recent years and whether the implementation of the Low Emission Zone (LEZ), an initiative designed to reduce air pollution, had an effect on asthma diagnosis incidence.

Approach

Date of first coded asthma diagnosis in electronic health records was gathered from 14 GP practices across Tower Hamlets between 2002-2013. A total of 100,702 patients were included in primary analysis. We examined monthly asthma incidence rates, carrying out an exploratory interrupted time series analysis, comparing two times periods 2002-2007 and 2008-2012, before and after the date of first implementation of the LEZ. Air Quality data on five major air pollutants (NO2, NOx, O3, PM10, PM2.5) were collected and modelled according to postcodes of the included participants.

Findings

Results showed a trend towards a general reduction in new asthma diagnosis incidence over time from 10 per 1000 person years to 5 per 1000 person years. Age stratification analysis performed did not reveal this change in incidence as suggested by primary analysis. This trend does not seem to be affected by the implementation of the LEZ within London.

Consequences

Results show general trends of reduced rates of asthma diagnosis over time. These could be real or artifactual, for example, reflecting Read coding conventions changing over time, or changes in population demographics in East London. Results suggest potential relationship with PM10 concentration but not statistically tested, with further work required.