Spatio-temporal associations of air pollutant concentrations, GP respiratory consultations and respiratory inhaler prescriptions: a 5-year study of primary care in the borough of Lambeth, South London

BACKGROUND: Although the associations of outdoor air pollution exposure with mortality and hospital admissions are well established, few previous studies have reported on primary care clinical and prescribing data. We assessed the associations of short and long-term pollutant exposures with General Practitioner respiratory consultations and inhaler prescriptions. METHODS: Daily primary care data, for 2009–2013, were obtained from Lambeth DataNet (LDN), an anonymised dataset containing coded data from all patients (1.2 million) registered at general practices in Lambeth, an inner-city south London borough. Counts of respiratory consultations and inhaler prescriptions by day and Lower Super Output Area (LSOA) of residence were constructed. We developed models for predicting daily PM(2.5), PM(10), NO(2) and O(3) per LSOA. We used spatio-temporal mixed effects zero inflated negative binomial models to investigate the simultaneous short- and long-term effects of exposure to pollutants on the number of events. RESULTS: The mean concentrations of NO(2), PM(10), PM(2.5) and O(3) over the study period were 50.7, 21.2, 15.6, and 49.9 μg/m(3) respectively, with all pollutants except NO(2) having much larger temporal rather than spatial variability. Following short-term exposure increases to PM(10), NO(2) and PM(2.5) the number of consultations and inhaler prescriptions were found to increase, especially for PM(10) exposure in children which was associated with increases in daily respiratory consultations of 3.4% and inhaler prescriptions of 0.8%, per PM(10) interquartile range (IQR) increase. Associations further increased after adjustment for weekly average exposures, rising to 6.1 and 1.2%, respectively, for weekly average PM(10) exposure. In contrast, a short-term increase in O(3) exposure was associated with decreased number of respiratory consultations. No association was found between long-term exposures to PM(10), PM(2.5) and NO(2) and number of respiratory consultations. Long-term exposure to NO(2) was associated with an increase (8%) in preventer inhaler prescriptions only. CONCLUSIONS: We found increases in the daily number of GP respiratory consultations and inhaler prescriptions following short-term increases in exposure to NO(2), PM(10) and PM(2.5). These associations are more pronounced in children and persist for at least a week. The association with long term exposure to NO(2) and preventer inhaler prescriptions indicates likely increased chronic respiratory morbidity.