Objective: To investigate risk factors for asthma in farmers.
Methods: A questionnaire was sent to all farms (n = 2499) and to 2900 controls aged 19-65 years from the general population in the county of Uppsala. Sixty per cent of the farms (1514 men and 248 women) and 64% of the controls (900 men, 943 women) responded.
Results: Only 13% of the male farmers had heredity for allergy compared to 24% of the controls, and fewer farmers were smokers. After adjusting for confounders, male farmers had a significantly lower prevalence of doctor-diagnosed asthma and nocturnal breathlessness than the controls (OR 0.75, 95%CI 0.57-0.98 and OR 0.61, 95%CI 0.44-0.84), but a significantly higher prevalence of work-related wheeze (OR 1.74, 95%CI 1.30-2.35). The risk for asthma increased with age in the farmers. Of male farmers with asthma, 70% had developed asthma after the age of 21, in contrast with only 30% of the asthmatic controls. The young female farmers had a high prevalence of asthma.
Conclusion: Male farmers have an increased risk of work-related wheeze and adult-onset asthma increasing with age despite a lower prevalence of asthma during childhood and young age than in the general population.