To date, we do not know, over the past two decades, the proportion of our population (prevalence) that have asthma at the time of measurement, the change in that proportion, or the proportion that are using asthma medication. The only measurements of prevalence have been for a single year, or have only looked at people who have ever been diagnosed with asthma (lifetime prevalence). However, asthma can resolve, so people who had asthma as a child and then grew out of it, will be included in a lifetime prevalence estimate but not in a current asthma prevalence. This distinction is important for healthcare planning. Furthermore, prevalence has not been measured since 2012, but there has been a change in the trend of prevalence in many other countries since then.
Asthma is very costly to the NHS, over £1 billion annually, predominantly due to asthma drug costs (3 of the top 5 most expensive NHS drugs). There are many asthma treatment options, each with different costs. This study aims to estimate the annual prevalence of current asthma, and prevalence of asthma medication use, over the past two decades. These findings will be beneficial for health policy planning (both clinical and economic).
The object of this study is to estimate an up-to-date prevalence of current asthma in the UK, and the temporal trends in annual prevalence over the past two decades. Annual prevalence will be stratified by age, gender, region, socioeconomic status (for patients with linked IMD data), asthma medication and asthma severity. Current asthma patients will be identified, using validated Read codes, between 2000 and 2017. The overall annual number of patients registered in the CPRD will be used as the denominator. Annual prevalence and temporal trends of patients experiencing ?1 asthma attack per year will also be estimated (only patients with linked HES data).
According to clinical guidelines, asthma patients should have their asthma medication changed according to their symptoms, however, it is not known how often this occurs in clinical practice (especially whether patients have their medication reduced when their disease is stable). To determine this, we will carry out a descriptive historical cohort study; asthma patients will be categorised by their asthma medication (according to UK clinical guidelines) in the 12-months leading up to their study start date. Patients medication category will then be categorised again every 12 months thereafter, this will capture temporal changes in medication categorisation.
Prevalence of current asthma
Prevalence of patients with ?1 exacerbation
Prevalence of the use of asthma drugs
Temporal changes of asthma drug use
Jennifer Quint - Chief Investigator - Imperial College London
Chloe Bloom - Corresponding Applicant - Imperial College London
HES Admitted Patient Care;ONS Death Registration Data;Patient Level Index of Multiple Deprivation