Mortality by Cause of Death and Risk Behaviors in Farmers Versus Non-farmers: the Importance of Avoiding the Healthy Worker Effect

Objectives: To compare mortality by cancer sites and by other specific causes of death, and the prevalence of risk behaviors in farmers and non-farmers in Spain.

Methods: Mortality by cause of death was calculated based on a longitudinal study with 10-years follow-up of 9.5 million men and 6 million women aged 20-64 years who were employed in 2001. The prevalence of risk behaviors was calculated from the 2001 National Health Survey in the 6464 employed men and 5573 employed women aged 20-64. The study subjects were grouped as farmers and non-farmers. For each cause of death, we estimated the ratio of age-standardized mortality rates, and for each risk behavior we estimated the age-standardized prevalence ratio in farmers versus non-farmers.

Results: In men, the mortality rate for most cancer sites did not differ significantly between farmers and non-farmers, except for cancers of the lip, oral cavity, stomach, larynx and skin epidermoid carcinoma-which was higher in farmers-and cancers of the liver, pancreas and mesothelioma-which was lower in farmers. In contrast, farmers had a higher rate of mortality from most other diseases and from external causes of death. In women, farmers showed lower mortality from lung cancer, breast cancer and chronic lower respiratory disease, and higher mortality from external causes. The prevalence of smoking, excessive alcohol consumption, physical inactivity and obesity was higher in farmers than in non-farmers, except smoking and excessive alcohol consumption in women where prevalence was lower in farmers.

Conclusions: Findings are different from those found in other studies. In men, greater exposure to the sun and the higher prevalence of risk behaviors in farmers could explain their excess mortality from some cancer sites and the other causes of death. However, other factors may be behind this excess risk of mortality from these causes, given that farmers did not show higher mortality from some cancers related to smoking. In women, no differences were observed in mortality rate for majority of causes of death between farmers and non-farmers.