Background: asthma is a global public health problem and it is therefore important to understand all its risk factors and causes.

Aim: to explore the influence of host and environmental risk factors on the asthma development in the general population.

Methods:  1145 subjects (females: 54.1%; 8-78 yr) living in Pisa and Cascina, Italy, were investigated in 1991-93 (PI baseline - PIb) and 2009-2011 (PI follow-up - PIfu) through a questionnaire on health status and risk factors. Incidence of asthma was assessed as presence of diagnosis +/- symptoms of asthma at PIfu in subjects without asthma diagnosis/symptoms at PIb (n=965). By logistic regression models, stratified by high/low (>/< median=51.98%) agricultural space exposure within 1 km from home address (CORINE program), the association between incidence of asthma and overweight (25 ? body mass index-BMI < 30 kg/m2), obesity (BMI ? 30 kg/m2) was assessed adjusting for sex, age, education, smoking habits and active lifestyle (active commuting mode, >2 hours a day outdoors) at PIb. Results: At PIb, overweight and obesity prevalence rates were 37.1%, 11.5%, respectively; mean agricultural space was 44.7% (±21.2).  Asthma incidence rate was 9.8% at PIfu. Asthma incidence was significantly associated with obesity (Odds Ratio 2.39; 95% Confidence Interval 1.02-5.61) only in subjects with high agricultural space exposure at PIb.

Conclusions: obesity can be a risk factor for the development of asthma, particularly in subjects exposed to agricultural space. This could be due to exposure to agricultural pesticides, endocrine disruptors related to both obesity and asthma.  This information can be very useful to reduce asthma burden in the general population.