The association between salivary cortisone level and structural change of Limbic system based on differences in blood heavy metal concentration among Korean firefighters

Abstract

TPS 792: Occupational health 2, Exhibition Hall, Ground floor, August 27, 2019, 3:00 PM - 4:30 PM Introduction: The limbic system is an anatomical structure that plays a pivotal role in motivation, emotion, learning and memory. Firefighters are chronically exposed to violence, trauma and other threats. They are also constantly exposed to a variety of environmental hazardous substances. This study focused on the association of limbic system atrophy and salivary cortisone known as stress hormone. Finally, we analyzed whether there is a difference in the relationship between cortisone level and the stuctural change of the limbic system among the subgroups with different concentrations of heavy metals. Methods: Subjects from Firefighter Research Enhancement of Safty&Health (FRESH) cohort in South Korea were used in analysis. Saliva sample was collected at 1:00 pm on all participants. Of the total subjects, 349 measured cortical thickness, and brain volume for all areas of the brain by brain 3T MRI. We divide the subjects into two subgroups each based on the median value of the heavy metal-lead and cadmium- concentration in the blood. Furthermore, to show a correlation between salivary cortisone and structural change of the limbic system, the generalized linear models was used. Results: In both groups with lower blood lead concentrations (under 1.900ug/dL) and lower cadmium (under 0.793ug/L), there was no statistically significant association between salivary cortisone and the limbic structure. In group with higher blood lead concentrations, higher salivary cortisone showed a decline left (β=-45.3316, p=0.0044) and right (β=-35.2435, p=0.0232) hippocampus, and left (β=-0.0115, p=0.0395) and right (β=-0.0126, p=0.0201) cingulate gyrus. In group with higher blood cadmium concentrations, higher salivary cortisone showed a decline left (β=-45.1016, p=0.0032) and right (β=-37.1952, p=0.0081) hippocampus, left (β=-19.3342, p=0.0076) and right (β=-18.1622, p=0.0129) thalamus, and right cingulate(β=-0.0113, p=0.0245). Conclusions: The results of this analysis indicate that salivary cortisone level was partially related with volume and thickness of some limbic system structure in subjects with relatively high blood heavy metal concentration even within normal levels.