Objectives: Studies suggest that mitochondrial dysfunction underlies some forms of sepsis-induced organ failure. We sought to test the hypothesis that variations in mitochondrial DNA haplogroup affect susceptibility to sepsis-associated delirium, a common manifestation of acute brain dysfunction during sepsis.
Design: Retrospective cohort study.
Setting: Medical and surgical ICUs at a large tertiary care center.
Patients: Caucasian and African American adults with sepsis.
Measurements and main results: We determined each patient's mitochondrial DNA haplogroup using single-nucleotide polymorphisms genotyping data in a DNA databank and extracted outcomes from linked electronic medical records. We then used zero-inflated negative binomial regression to analyze age-adjusted associations between mitochondrial DNA haplogroups and duration of delirium, identified using the Confusion Assessment Method for the ICU. Eight-hundred ten patients accounted for 958 sepsis admissions, with 802 (84%) by Caucasians and 156 (16%) by African Americans. In total, 795 patient admissions (83%) involved one or more days of delirium. The 7% of Caucasians belonging to mitochondrial DNA haplogroup clade IWX experienced more delirium than the 49% in haplogroup H, the most common Caucasian haplogroup (age-adjusted rate ratio for delirium 1.36; 95% CI, 1.13-1.64; p = 0.001). Alternatively, among African Americans the 24% in haplogroup L2 experienced less delirium than those in haplogroup L3, the most common African haplogroup (adjusted rate ratio for delirium 0.60; 95% CI, 0.38-0.94; p = 0.03).
Conclusions: Variations in mitochondrial DNA are associated with development of and protection from delirium in Caucasians and African Americans during sepsis. Future studies are now required to determine whether mitochondrial DNA and mitochondrial dysfunction contribute to the pathogenesis of delirium during sepsis so that targeted treatments can be developed.