Risk factors and costs associated with an asthma attack.

BACKGROUND A study was undertaken to identify asthma patients at risk of an attack and to assess the economic impact of treatment strategies. METHODS A retrospective cohort analysis of a representative data set of 12 203 patients with asthma in the UK over a one year period was performed. Logistic multiple regression was used to model the probability of an attack occurring using a set of categorised predictor factors. Health service costs were calculated by applying published average unit costs to the patient resource data. The main outcome measures were attack incidence, health service resource use, drug treatment, and cost estimates for most aspects of asthma related health care. RESULTS Children under five years of age accounted for 597 patients (5%), 3362 (28%) were aged 5-15 years, 4315 (35%) 16-44, 3446 (28%) 45-74, and 483 (4%) were aged over 74 years. A total of 9016 patients (74%) were on some form of prophylactic asthma medication; 2653 (22%) experienced an attack in the year data collection occurred. Overall health care expenditure was estimated at pound2.04 million. The average cost per patient who had an attack was pound381 compared with pound108 for those who did not, an increase of more than 3.5 times. In those aged under five and those over 75 years of age there were no significant markers to identify risk, but both groups were small in size. The level of treatment step in the British Thoracic Society (BTS) asthma guidelines was a statistically significant factor for all other age groups. Night time symptoms were significant in the 5-15, 16-44 and 45-74 age groups, exercise induced symptoms were only significant for the 5-15 age group, and poor inhaler technique in the 16-44 age group. CONCLUSIONS Patients at any treatment step of the BTS asthma guidelines are at risk of an asthma attack, the risk increasing as the treatment step increases. Poorly controlled asthma may have a considerable impact on health care costs. Appropriate targeting of preventive measures could therefore reduce overall health care costs and the growing pressures on hospital services associated with asthma management.