Posttraumatic stress disorder, major depression, and mild cognitive impairment: A cohort study of world trade center responders.

BACKGROUND: World Trade Center (WTC) responders have elevated risk of posttraumatic stress disorder (PTSD), major depressive episodes (MDEs), and mild cognitive impairment (MCI). In a sample of 337 WTC responders from the Fire Department of the City of New York (FDNY), we estimated the proportion of MCI cases explained by PTSD and MDE. METHODS: We fit quasi-Poisson regressions, adjusting for covariates, to estimate risk ratios (RRs) and population-attributable fractions (PAFs), and explored associations between a symptom count and MCI, as well as individual cognitive tests. MEASURES: PTSD and MDE were diagnosed with the SCID-5. MCI was defined algorithmically using objective testing (HVLT subtests, COWA, SDMT, TMT-A/B), self-reported concern (CFI >0), and excluding severe naming impairment. The cohort was predominantly firefighters; occupational requirements preserve activities of daily living. RESULTS: PTSD (RR=1.90, 95 % CI = [1.53-2.36]), MDE (RR=1.62, 95 % CI = [1.16-2.27]), and comorbid PTSD/MDE (RR=2.31, 95 % CI = [1.74-3.06]) conferred higher risk of MCI. The combined PAF for PTSD, MDE, and their comorbidity was 11.7 % (95 % CI = [6.1 %-18.1 %]). Symptom burden was associated with higher MCI risk (RR = 1.11, 95 % CI = [1.08-1.14]), and worse visuospatial learning/recall and verbal recognition (ρ range = [-0.13 to -0.20]). CONCLUSION: Over 20 years after the precipitating trauma, PTSD, MDE, and their comorbidity accounted for a meaningful share of MCI cases, although most cases (>85 %) were not attributable to these disorders. Findings highlight visuospatial learning and memory as most strongly linked to psychiatric symptoms in this cohort.