Characteristics of adults with and without cystic fibrosis-related diabetes

The prevalence of diabetes in adults with cystic fibrosis (CF) approximates 25%, yet few studies have defined risk factors. We examined the association between biochemical and clinical factors and CF-related diabetes.

We performed a study in adults with CF in 2004 in Cambridgeshire, UK. Of 160 individuals, 51 had diabetes (cases) on the basis of medical history or screening using a 75-g oral glucose tolerance test, and 107 did not have diabetes (control subjects); two were excluded. We used logistic regression to model the cross-sectional association between potential risk factors and diabetes.

The mean age was 26 (16-58) years, mean body mass index (BMI) was 21 (16-28) kg/m(2), and mean forced expiratory volume in 1 s was 60 +/- 24% (mean +/- sd). All of the cases and 88% of control subjects had pancreatic insufficiency. Cases did not differ from control subjects with respect to age, sex, body mass index, or dose of oral pancreatic enzymes. Cases were more likely to have low serum magnesium, haemoglobin, and pulmonary function, and higher serum gamma-glutamyl transferase (GGT) activity, plasma fibrinogen levels, erythrocyte sedimentation rate, use of oral corticosteroids, and number of CF-related complications. In multivariate analyses, GGT, previous organ transplantation, plasma fibrinogen and the presence of CF-related complications were independently associated with diabetes, after controlling for corticosteroid use.

These data confirm the high prevalence of diabetes in adults with CF, and identify plasma fibrinogen and GGT, and organ transplantation as factors independently associated with CF-related diabetes. A prospective study would clarify the nature of these associations.