OBJECTIVE Diabetes is common in cystic fibrosis and increases the risk of death, yet the role of hyperglycemia remains unproven. An association between glycemia and mortality would provide compelling evidence to support glucose lowering in cystic fibrosis–related diabetes (CFRD).
RESEARCH DESIGN AND METHODS Using the U.K. Cystic Fibrosis Registry, we analyzed longitudinal data from 2006 to 2009 in 520 individuals with diabetes. We tested the association between HbA1c and mortality.
RESULTS During a median follow-up of 2 years, 36 patients died. The median value of HbA1c was higher in those who died (7.3%) than in those who did not (6.7%). An HbA1c value of ≥6.5% was associated with a threefold increased risk of death (hazard ratio 3.2 [95% CI 1.4–7.3]; P = 0.005) independent of potential confounders.
CONCLUSIONS Hyperglycemia trebles the risk of death in patients with CFRD. These findings provide epidemiologic support for continued efforts to improve glycemic control.
Diabetes frequently complicates cystic fibrosis. Cystic fibrosis–related diabetes (CFRD) has an incidence in teenagers of up to 6% per year and a prevalence in adults of >30% (1,2). Diabetes further elevates the already high mortality rates in cystic fibrosis (3–5). In individuals without cystic fibrosis, diabetes increases the risk of death, and in individuals with diabetes, hyperglycemia increases the risk of death (6,7). However, no study of CFRD using national data has investigated whether hyperglycemia, per se, increases the risk of death; likewise, no trial has tested whether controlling blood glucose prolongs survival. Proving an association between glycemia and mortality in cystic fibrosis would provide compelling observational evidence to inform clinical practice. Using the U.K. Cystic Fibrosis Registry, we performed longitudinal analyses to test the association between glycemia, as measured by HbA1c, and mortality in individuals with CFRD.