Longitudinal studies on the effect of farming on lung function in young participants are few. Our objective was to explore if exposure to farming impaired lung function in young adults.
We studied 1964 farming students and 407 controls in 1992/2004, and carried out follow-up in 2007/2008. Spirometry, skin prick test and bronchial hyper-responsiveness (BHR) were assessed, height and weight measured, and questionnaires covering health and occupation were collected. Cumulative dust and endotoxin exposures were estimated from modelled personal dust measurements. Lung function effect was expressed as change in z-score during follow-up using the Global Lung Initiative 2012 project prediction equations. Longitudinal data were available for 1134 young participants =25 years at baseline.
We found no differences in lung function ?z-scores between farmers and controls, however, adjusted multivariable linear regression showed a negative effect among current farmers on ?zFEV1 (forced expiratory volume in 1 s; -0.12, p=0.006) and ?zFEV1/FVC (forced vital capacity; -0.15, p=0.009) compared to ex-farmers. An interaction was found between sex and farming, showing that current farming suppresses ?zFEV1 and ?zFVC more among females. Smoking in farmers had a deleterious effect on ?zFEV1, which was not seen in controls, though no significant interaction was found. Farm upbringing protected against impairment of lung function, and BHR at baseline had a deleterious effect on ?zFEV1 only in those not raised on a farm.
We conclude that being a current farmer is associated with a negative effect on lung function, when compared to ex-farmers, with females being more susceptible. Being raised on a farm protects against the adverse effect of BHR on change in lung function.