Effects of CO Level on Pain, Sensory Function, and Subjective Health

Carbon monoxide (CO) is a colorless and odorless gas that can enter the human body through environmental exposure and especially tobacco use. CO binds to hemoglobin with a much higher affinity than oxygen, thereby reducing oxygen transport to tissues. This condition may lead to various physiological and psychological effects, particularly on the nervous system. In the literature, CO exposure has mainly been investigated in the context of acute poisoning cases and smoking-related effects. However, studies evaluating the effects of low-level and chronic CO exposure-more commonly encountered in the general population-on pain perception, sensory functions, and psychological status are limited. Tobacco smoke is an important source of CO, and exhaled CO levels have been shown to be significantly higher in smokers and associated with various neurocognitive changes. Evidence suggests that CO exposure may influence anxiety, depression, attention, and cognitive functions. In addition, some studies indicate that CO may affect brain regions involved in pain perception and emotional regulation. However, there is insufficient research examining the relationship between low-level carbon monoxide exposure and pain threshold, sensory functions, anxiety, depression, and subjective health complaints within the same study framework. This study aims to evaluate the relationship between exhaled carbon monoxide (CO) levels and pain threshold, sensory functions, anxiety, depression, and subjective health complaints in healthy adults. By examining the multidimensional effects of low-level CO exposure, the study seeks to fill an important gap in the literature and provide a more comprehensive understanding of this issue.

NCT Number	NCT07571941
Lead Sponsor	Izmir Democracy University
Conditions	Carbon Monoxide, Pain Perception, Sensory Thresholds, Anxiety, Depression, Tobacco Smoking
Enrollment	70 participants
Start Date	2026-06-01
Primary Completion	2026-07-01 (estimated)
Study Completion	2026-09-01 (estimated)
Updated on ClinicalTrials.gov	2026-05-07