Elevated Hemoglobin A1c and the Risk of Developing ARDS in Two Cohort Studies

Background: Only a subset of patients at risk for ARDS go on to develop it, and the contribution of preexisting comorbidities (eg, diabetes) to ARDS risk is not well understood. Prior studies of the association between diabetes and ARDS have yielded conflicting results.

Research question: Does assessing ARDS risk based on hemoglobin A1c (HbA1c) as a marker of long-term blood glucose levels, rather than a charted diagnosis of diabetes, clarify the relationship between diabetes and ARDS?

Study design and methods: Using data from two prospective observational cohorts of critically ill adults (Validating Acute Lung Injury Biomarkers for Diagnosis [VALID] and Early Assessment of Renal and Lung Injury [EARLI]), we analyzed the association between clinical HbA1c category and development of ARDS in patients with a risk factor for ARDS and at least one clinical HbA1c measurement within the 180 days prior through 14 days after enrollment.

Results: A total of 599 patients in VALID and 276 in EARLI met inclusion criteria, of whom 164 and 58 developed ARDS, respectively. Patients with a charted diagnosis of diabetes were not shown to be more likely to develop ARDS (VALID: 24.6% ARDS in those categorized as nondiabetic vs 30.0% in those categorized as diabetic, P = .14; EARLI: 19.6% vs 22.8%, respectively; P = .55). However, in VALID, patients categorized as diabetic with inadequate glycemic control based on their HbA1c had an increased risk of developing ARDS compared with those with nondiabetic HbA1c (20.9% vs 34.0%, respectively; P = .0073), a finding that persisted in multivariable analysis (OR for those categorized as diabetic with inadequate glycemic control vs those categorized as nondiabetic range HbA1c, 1.25; 95% CI, 1.01-1.57). These findings were not reproduced in the smaller EARLI cohort, but were appreciated when the cohorts were combined for analysis.

Interpretation: Elevated HbA1c may be associated with risk of developing ARDS, independent of clinical diagnosis of diabetes, but prospective validation is needed. If confirmed, these findings suggest that inadequate glycemic control could be an unrecognized risk factor for ARDS.