Objectives Farming is filled with respiratory hazards: pesticide vapors, dusty fields, dangerous hydrogen sulfide accumulations in manure pits and pump sumps, nitrogen dioxide in conventional silos, and many others. Despite the recognition of respiratory hazards, this problem has not been fully investigated at the world level after harmonization of data. We used data from the AGRICOH consortium, a collective of prospective cohorts of agricultural workers, to assess respiratory disease prevalence among adults in 18 cohorts representing over 200,000 (118,520 men, 92,712 women) farmers, farmworkers, and their spouses from six continents.

Methods Cohorts collected data between 1992–2016 and ranged in size from 200 to >128,000 individuals; 44% of participants were female. Farming practices varied from subsistence farming to large scale industrial agriculture. All cohorts provided respiratory outcome information for their cohort based on their study definitions. The majority of outcomes were based on self-report using standard respiratory questionnaires; the greatest variability in assessment methods was associated with chronic obstructive pulmonary disease (COPD).

Results The median prevalence was 18.6% for cough, 13.3% for phlegm, and 15.0% for wheeze and was higher in men than in women, with the greatest difference for phlegm (17% vs. 10%). For asthma, the median prevalence was 7.2% and was higher in women (7.8% vs. 6.5%). The relative proportion of allergic asthma varied among cohorts. In two of eight cohorts for women and two of seven cohorts for men, allergic asthma was more common than non-allergic asthma. The median prevalence of COPD was 4.5%. Men suffered more than women from COPD (5.5% vs. 4.0%).

Conclusion These findings indicate that respiratory outcomes are common among farmers around the world despite the differences in agricultural production. Both allergic and non-allergic asthma exist among farmers.