Reduced cortical thickness in World Trade Center responders with cognitive impairment

Abstract

Introduction: This study examined cortical thickness (CTX) in World Trade Center (WTC) responders with cognitive impairment (CI).

Methods: WTC responders (N = 99) with/without CI, recruited from an epidemiologic study, completed a T1-MPRAGE protocol. CTX was automatically computed in 34 regions of interest. Region-based and surface-based morphometry examined CTX in CI versus unimpaired responders. CTX was automatically computed in 34 regions of interest. Region-based measures were also compared to published norms.

Results: Participants were 55.8 (SD = 0.52) years old; 48 had CI. Compared to unimpaired responders, global mean CTX was reduced in CI and across 21/34 cortical subregions. Surface-based analyses revealed reduced CTX across frontal, temporal, and parietal lobes when adjusting for multiple comparisons. Both CI and unimpaired WTC groups had reduced CTX in the entorhinal and temporal cortices compared to published normative data.

Discussion: Results from the first structural magnetic resonance imaging study in WTC responders identified reduced CTX consistent with a neurodegenerative disease of unknown etiology.

Keywords: World Trade Center responders; cognitive impairment; cortical thickness.

FIGURE 1

Absolute differences in mean whole‐brain mean cortical thickness expressed in mm by patient diagnostic group. Note: Group differences were evident across groups when using one‐way analysis of variance across all group profiles (P = .002) that was concentrated in cognitively impaired responders. 95% confidence intervals shown using capped error bars. *Statistically significant at P < .05; ^o P = .055

FIGURE 2

Heat map showing levels of association between dimensional measures of cognition and posttraumatic stress disorder and regional measures of cortical thickness (CTX). Note: Coefficients were transformed so that increases in dimensional scores are consistent with worse outcomes. Stanardized Mean Differences (Cohen's D) were estimated from generalized linear modeling; all coefficients deemed statistically significant upon adjusting for the false discovery rate (FDR = 0.05) were reported. Red indicates reduced CTX; blue indicates increased CTX.

FIGURE 3

Group‐wise analyses using surface‐based morphometry comparing cognitively impaired to cognitively unimpaired responders Note: Group‐wise analyses using surface‐based morphometry identified areas of reduced cortical thickness (CTX) are shown since no regions with increased cortical thickness were identified. Regions lacking significant differences in CTX between groups are shown in gray; cluster locations provided in Table S2 in supporting information. Figure generated using Computational Anatomy Toolbox (CAT12)