Magnetic resonance lmaging of odor associated irritant effects: Multimodal objectification of the prediction of irritant effects in susceptible persons, and their possible influence on occupational risks and work performance

Status:

completed 03/2024

Aims:

A key topic in the current discussion on setting limits for substances with local effects is the consideration of susceptible groups by applying appropriate extrapolation factors. A critical issue in this context is the growing number of workers with chronic illnesses, which may be associated with increased sensitivity to odors and irritants. Strong odors in the workplace may pose a safety risk to this group, as they may become distracted from their tasks (distraction effect), potentially leading to accidents. The research project aimed to investigate biomarkers for identifying and characterizing susceptible groups in terms of odor and irritant sensitivity, using migraine sufferers as an example. Additionally, healthy individuals with a strong respiratory response to capsaicin were studied to evaluate the research hypotheses in a group without chronic illness.

Activities/Methods:

To achieve the objectives, imaging techniques and new investigative methods were employed. These included structural and functional MRI scans to examine the activity and connectivity of specific brain areas. GABA and PRESS spectroscopy were used to measure neurotransmitter concentrations, while Quantitative Sensory Testing (QST) assessed sensory sensitivity. Confocal Corneal Microscopy (CCM) was utilized to examine nerve fibers in the cornea, and n-back tasks of varying difficulty levels were employed to investigate the distraction effect of a nocebo odor on working memory.

Results:

The study showed multiple significant differences between migraine sufferers and control subjects. Migraine sufferers exhibited an increased branching density of pain fibers in the cornea, indicating heightened pain sensitivity. Additionally, lower GABA concentrations were observed in the insula, suggesting reduced inhibition of neuronal activity. These neurobiological changes led to increased neural connectivity in the brain, particularly in networks responsible for processing pain and sensory stimuli. Under nocebo stimulation, migraine sufferers reported significant impairment of well-being and exhibited greater distractibility at the neural level, though there was no significant impact on cognitive performance at the behavioral level. A similar increased sensitivity to odors and irritants is expected in other common chronic illnesses, such as asthma or other respiratory diseases.

In the capsaicin group, an increased pain sensitivity was observed, though it did not consistently correlate with the other biomarkers. The hypothesized increased sensitivity to odors and irritants could not be confirmed in this group of non-chronically ill individuals.

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