Severity and burden of asthma in Scotland–a full population study using the Prescribing Information system

In contrast to many epidemiological studies of asthma that have been limited to samples assumed to be representative of the national population from which they are drawn we have used routinely collected drug dispensing data for the whole Scottish population. Our aim was to use NHS Scotland’s Prescribing Information System (PIS) to describe asthma prevalence, asthma severity (BTS treatment steps) and asthma control (exacerbations, hospital / A&E episodes) in children and young adults. Methods For >95% of dispensed prescriptions in primary care between December 2009 and December 2012 a valid patient identifier is available including some socio-demographical characteristics (age-group, sex, socioeconomic status). Data were also linked to hospital admission and A&E event data to identify exacerbations and exclusion criteria. The analysis was limited to patients aged = 45 years to reduce contamination by COPD. Patients with non-asthma respiratory diagnoses were excluded. Results In the 3 year period about 395,000 patients received repeated medications for asthma with a monthly point prevalence of 255,000 asthma patients; equating to a prevalence of 7.0% of the 3.6 million people aged 0–45 registered with a GP in Scotland. These patients collected 5.6 million prescriptions for inhaled/oral asthma therapies and 253,000 short courses of oral corticosteroids were dispensed to these patients in primary care. Patients were categorised on a daily basis into BTS Steps 1- 5 according their medication use. As of June 2011: 83,663 (32.4%) of patients were in Step 1; 99,374 (38.5%) were in Step 2; 42,555, (16.5%) were Step 3; 27852 (10.8%) were Step 4, and 4,500 patients (1.7%) were Step 5 receiving daily oral corticosteroids. Table 1 presents the exacerbation rates for these patients, 1.9% of the patients received an emergency short course of prednisolone,. Conclusion This current and whole population database indicates that in Scotland asthma prevalence is about 7% in this age group. The proportion of asthma patients treated at Steps 3–5 (25%) is greater than the often quoted 15%. Although proportionately small, a sizeable number of patients (~7000) with Step 1 and 2 asthma had at least one exacerbation requiring short course prednisolone and/or hospital contact over a three year period.