Trends in pulmonary function in patients with cystic fibrosis correlate with the degree of glucose intolerance at baseline

In patients with cystic fibrosis, CF-related diabetes mellitus (CFRD) has b een associated with increased morbidity and mortality. Whether glucose into lerance is also associated with poor outcomes is unclear. To better define these relationships we prospectively followed a group of 152 patients with CF without diabetes for 4 yr, Patients were classified as having normal glu cose tolerance (NGT), impaired glucose tolerance (IGT), or CFRD without fas ting hyperglycemia (CFRD-No FH). FEV1, FVC, and body mass index (BMI) were measured at baseline and quarterly. At baseline 45% of the patients had NGT , 38.8% had IGT, and 15.8% had CFRD-No FH. FEV1, FVC, and BMI at baseline w ere comparable among these groups (all p > 0.1). After 4 yr an overall decl ine in FEV1 and FVC occurred, with no change in BMI. The rates of decline f or FEV1 and FVC correlated with the glucose tolerance groups, with the high est rates of decline occurring among the CFRD-No FH group. In addition, pat ients in the lowest quartile for insulin production at baseline experienced the highest rates of pulmonary function decline over time, suggesting a re lationship between insulin deficiency and clinical deterioration. We conclu de that the degree of glucose intolerance is a strong determinant of future lung function decline in patients with CF.