September 10, 2026

@michaelokun

Could carbon monoxide hold a clue to why smoking has been linked to a lower risk of Parkinson’s? Carbon monoxide (CO) is a gas best known for its toxicity, however our bodies also produce tiny amounts of CO where it functions as a signaling molecule. Bueno Lopez and colleagues describe in a new paper in JAMA Neurology how higher exhaled CO levels were associated w/ a lower future risk of Parkinson’s disease, including among folks who never smoked. The accompanying editorial by Darweesh, Remz and Goldman asks the provocative question of whether CO could be one piece of the long-standing smoking-Parkinson’s puzzle. Key points: - More than 512,000 adults in China were followed for approximately 12 years, and 1,131 developed Parkinson’s disease. - Among folks who never smoked, higher exhaled CO was associated w/ progressively lower Parkinson’s risk, and the highest CO group had about a 35% lower risk compared w/ the lowest group. - The editorial appropriately pumps the brakes: this is an association, not proof that CO prevents Parkinson’s, and confounding, regional differences and variability in measuring exhaled CO remain important concerns. My take: This is one of those fascinating Parkinson’s observations that should make us curious, but not careless. Smoking is harmful and nobody should smoke or expose themselves to carbon monoxide in an attempt to prevent Parkinson’s. The exciting question is whether we can identify the biological mechanism hiding inside this epidemiologic paradox and someday separate a potentially protective pathway from the enormous harms of smoking and toxic CO exposure. The nicotine story taught us humility: epidemiology suggested a protective association, yet nicotine itself has not translated into benefit in human trials.