Risk of exacerbations in COPD and asthma patients living in the neighbourhood of livestock farms: Observational study using longitudinal data

OBJECTIVE: Living in an area with a high density of livestock farms has been associated with adverse respiratory health effects in some studies. As patients with COPD and asthma already have a compromised respiratory function and chronic airway inflammation, they are expected to be at increased risk for adverse respiratory health effects. The objective of this study was to assess the association between livestock exposure and exacerbations in COPD and asthma.

METHODS: 899 COPD and 2546 asthma patients from 15 general practices in a rural area with a high livestock density and 933 COPD and 2310 asthma patients from 15 practices in a control area in the Netherlands were included. Occurrence of exacerbations was based on the pharmaceutical treatment of exacerbations in COPD and asthma patients using 2006-2012 prescription data of electronic medical records. Farm exposure was assessed by comparing the study area with the control area, and with individual exposure estimates in the study area using Geographic Information System data.

RESULTS: The exacerbation rate was higher in the study area compared with the control area in COPD (IRR: 1.28; 95%CI: 1.06-1.55), but not in asthma patients (IRR: 0.87; 95%CI: 0.72-1.05). In general, individual exposure estimates in the study area were not associated with exacerbations. COPD patients living within a 500m radius of up to12,499 chickens had a 36% higher exacerbation rate (IRR: 1.36; 95%CI: 1.03-1.79).

CONCLUSIONS: Living in an area with a high livestock density is a risk factor for exacerbations in COPD patients. The environmental exposure responsible for this increased risk remains to be elucidated.