Association of CBC-derived indices of inflammation with mortality in patients with PTSD

Posttraumatic stress disorder (PTSD) has been associated with immune activation and inflammation. Current methods of measuring inflammation in electronic health records (EHR) data are limited. The present study sought to leverage complete blood count (CBC)-derived indices of inflammation to study the effect of inflammation on mortality following PTSD diagnosis.

We used latent trajectory analysis to dichotomize six CBC-derived indices of inflammation - systemic immune response index (SIRI), systemic immune inflammation index (SII), aggregate index of systemic inflammation (AISI), monocyte-to-lymphocyte ratio (MLR), neutrophil-to-leukocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) - into low and high inflammatory groups. These groups were used to test the effect of high inflammation on all-cause, cardiovascular, and suicide mortality following PTSD diagnosis. Confounding between inflammatory groups was accounted for through propensity score weighting. Outcomes were assessed via weighted Cox proportional hazards regression models.

High inflammation in all indices except for PLR was associated with increased all-cause and cardiovascular mortality with the highest increase being for SIRI (HR: 1.35 [99.17% CI: 1.31, 1.39]; 1.50 [99.17% CI: 1.40, 1.60]). High inflammation in all six indices was associated with increased death by suicide with the greatest increase being for NLR (HR: 1.35 [99.17% CI: 1.17, 1.55]).

Given their widespread availability in EHR data and the association with increased mortality, CBC-derived indices of inflammation provide a promising avenue for future study of inflammation and PTSD.