Long-term Glycemia and Risk of Death in Cystic Fibrosis–Related Diabetes: A UK Cystic Fibrosis Registry Study

OBJECTIVE: Mortality risk is increased in cystic fibrosis (CF)-related diabetes, but its relationship with long-term glycemia is unclear. RESEARCH DESIGN AND METHODS: Using UK Cystic Fibrosis Registry data, we estimated the association between updated interval mean hemoglobin A1c (HbA1c) and mortality using Poisson regression to estimate mortality rates adjusted for age and sex and rate ratios adjusted for age, calendar year, sex, BMI, pulmonary function, and use of CF transmembrane conductance regulator modulators. RESULTS: Of 4,477 individuals contributing 31,311 person-years of follow-up, 758 died. Mortality rates increased progressively with higher updated interval mean HbA1c values. Compared with HbA1c ≤42 mmol/mol, adjusted mortality rate ratios were 1.41 (95% CI 1.15-1.73) for HbA1c >42-53 mmol/mol, 1.66 (95% CI 1.33-2.07) for HbA1c >53-69 mmol/mol, and 1.93 (95% CI 1.53-2.43) for HbA1c >69 mmol/mol. CONCLUSIONS: Higher HbA1c was associated with a clinically and statistically significant increase in mortality among individuals with CF-related diabetes.