Background Pulmonary inflammation is a major cause of decline in lung function in patients with cystic fibrosis and acute exacerbations may occur therefore slowing evolution of lung disease is a primary aim of CF therapy may precede the onset of chronic infection.

Methods An observational, cross-sectional transversal study including fifty seven patients evaluated the influence of factors potentially influent on the pulmonary function in CF patients.

The correlation of specific parameters like age, gender, nutritional status, CF related diabetes (CFRD), CF associated liver disease (CFLD), with the lung function expressed by FEV1 were studied. Multiple linear regression analysis was performed using FEV1 as a dependent variable and the following variables of interest: age, age-at-diagnosis, BMI, sex, pancreatic insufficiency, microbial infection, CFLD, CFRD as independent variables.

Results The correlation of the lung function, expressed by FEV1, was positive with BMI, every increase with a unit of BMI associated an increase of the FEV1 percentage with a mean value of 5.447 (95% CI 1.892; 9.002). The mean value of FEV1% decreased with 1.474 (95% CI −2.868; −0.080) for every increase unit increase in the patients age. With a stepwise multiple regression we obtained a significant model (p<0.001) in which the variability of FEV1 is expressed by sex (β=−0.297, p=0.059), BMI (β=0.498, p=0.004) and age (β=−0.332, p=0.039) in proportion of approximately 45% (R-square=0.435).

Conclusions The most important negative influence on the pulmonary status in our CF patients had the age, female sex and the MRSA colonisation, while the positive effect of enhanced BMI on the lung function was registered, as expected.