09 November 2015

High carbon monoxide in breath tied to stroke risk

High levels of carbon monoxide in the body might raise a person's odds for stroke or mini-stroke.

Seemingly healthy adults who exhale high levels of carbon monoxide may be at increased risk for stroke, a new study suggests.

Carbon monoxide is produced naturally by the body. According to the researchers, prior studies have linked high exhaled levels of carbon monoxide to an increased risk of heart disease.

Transient ischaemic attack

This new study was led by Dr Matthew Nayor, of Brigham and Women's Hospital in Boston, and included more than 3,300 healthy adults with no known history of stroke.

Read: Risk factors for having a stroke

All of the patients had their exhaled levels of carbon monoxide measured and health outcomes were then tracked for an average of nearly 13 years.

The study couldn't prove cause-and-effect. However, compared with those in the lowest one-third of levels of exhaled carbon monoxide, those in the middle one-third were 67 percent more likely to suffer a stroke or mini-stroke (transient ischaemic attack – TIA) during that time, and those in the top one-third were 97 percent more likely to suffer a stroke or mini-stroke, Nayor's team reported.

Read: Shingles up risk of stroke

Brain scans of nearly 2,000 of the participants showed that those with the highest levels of exhaled carbon monoxide were also more likely to have lower total brain volume, higher white matter volume and higher rates of silent stroke than those in the lowest one-third.

One expert wasn't surprised by the findings.

Preliminary findings

"It is well known that accidental or intentional inhalation of carbon monoxide is a dangerous situation that can lead to coma, brain damage and death," said Dr Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City. So, he said, it makes sense that high levels of the compound in the body might raise a person's odds for stroke or mini-stroke.

Read: Tomatoes reduce stroke risk

The study is to be presented at the annual meeting of the American Heart Association in Orlando, Florida. Findings presented at medical meetings are typically considered preliminary until published in a peer-reviewed journal. 

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