DIABETES-MELLITUS IN CYSTIC-FIBROSIS - EFFECT OF INSULIN THERAPY ON LUNG-FUNCTION AND INFECTIONS

The effect of insulin therapy on lung function and lung infections was studied in a retrospective case-control design in 18 diabetic cystic fibrosis (CF) patients; 18 non-diabetic CF patients, matched for sex, age and presence of chronic Pseudomonas aeruginosa lung infection, ser ved as controls. Parameters of CF clinical status were collected for s ix years before and two years after the onset of insulin therapy in th e diabetic patients. Before onset of insulin therapy, body mass index (BMI) and forced vital capacity (FVC) in (pre)diabetic patients deviat ed increasingly from those in control patients. Decreases in BMI and l ung function during the past three months before onset of insulin ther apy were reverted within three months of insulin therapy. From three m onths to two years after onset of insulin therapy, differences in BMI and lung function diminished between diabetic and control patients. Af ter two years of insulin therapy, BMI was similar in diabetic and non- diabetic patients and the percentage differences in forced expiratory volume in 1s (FEV(1)) and FVC between the two groups were similar to t hose found six years before the onset of insulin therapy. The finding that insulin therapy improves lung function in diabetic CF patients su ggests strongly that the insidious decline in lung function seen durin g the years before the diagnosis of diabetes mellitus results from the pre-diabetic condition. After onset of insulin therapy, the percentag es of sputum examinations positive for Haemophilus influenzae and Stre ptococcus pneumoniae decreased in the diabetic patients, whereas param eters of lung infections with P. aeruginosa and Staphylococcus aureus remained unchanged. In conclusion, since insulin therapy improves lung function and reduces the number of infections with H. influenzae and S. pneumoniae in diabetic CF patients, we suggest that insulin therapy should be started when diabetes mellitus is diagnosed.