Carbon monoxide (CO) is reported to cause around 30 deaths, 200 admissions and 4000 presentations to Emergency Departments each year in the UK. In the longer term, CO poisoning is recognised to cause persistent neurological problems (including impairments of thinking and behavioural changes), which can develop days to weeks after the initial exposure. However, the incidence of these long-term sequelae is unknown. In addition, there is evidence of long-lasting inflammatory changes in the brain and on-going brain cell injury, although how long this persists is also unknown.

Initial assessments of CO exposure can be unreliable if blood tests are not carried out within a relatively short period after the exposure and other biomarkers (such as imaging) are insensitive to detecting previous CO exposure. Certain proteins that are found in brain cells can be detected in the blood of individuals following brain injury and brain cell death. These proteins have been found to be raised in the acute period after minor head injury, persistently raised in patients with a traumatic brain injury and evidence of on going neurodegeneration (i.e. on going brain cell death) and in patients with various types of dementia.

The investigators will assess the presence of these proteins in the blood of 50 participants with proven CO exposure in the sub-acute to chronic timescale (2 weeks to 2 years). This has not been done before and will allow assessment of the presence of on going brain injury in these participants. The investigators will also assess cognitive (e.g. memory, attention and speed of thinking) and behavioural impairments in these participants to help characterise the common impairments suffered following CO exposure and relate these to evidence of persistent brain injury and severity of CO exposure.

Inclusion Criteria:

Individuals identified as having confirmed exposure to CO between 2 weeks to 2 years at time of assessment. CO exposure determined by either;

• documented COHb levels above 1.6% in non-smokers and above 6.3% in smokers.
• or, individuals with evidence of being exposed to raised levels of CO and symptoms

Exclusion Criteria:

• age <18 years
• actual or suspected smoke inhalation
• significant neurological or psychiatric illness prior to CO exposure
• inability to provide consent

50 individuals with confirmed evidence of CO exposure will be recruited.

Individual participant data that underlie the results reported in this article, after deidentification. Proposals should be directed to peter.jenkins1@nhs.net. To gain access, data requestors will need to sign a data access agreement.

Proposals may be submitted up to 36 months following article publication. After 36 months the data will be available in our University's data warehouse but without investigator support other than deposited metadata.

Researchers who provide a methodologically sound proposal.