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A large study of over 500,000 adults found that higher exhaled carbon monoxide (CO) levels — even in non-smokers — were linked to a significantly lower risk of Parkinson's disease. The findings suggest CO itself, not nicotine, may be the protective factor behind the long-puzzling smoking-Parkinson's connection. Researchers say this supports ongoing clinical trials testing low-dose CO as a potential Parkinson's therapy.
For decades, scientists have noticed that smokers have a lower risk of Parkinson's disease (PD) — but nobody could quite explain why. Nicotine was the prime suspect, but a clinical trial of nicotine patches failed to slow disease progression. Now, a large study published in JAMA Neurology points to a surprising new candidate: carbon monoxide (CO).
Researchers analyzed data from over 512,000 adults and found that higher exhaled CO levels were associated with a lower PD risk — not just in smokers, but in never-smokers too. That dose-dependent relationship in non-smokers is a key clue, suggesting CO itself may be the protective agent rather than anything else in cigarette smoke. At low concentrations, CO acts as a natural signaling molecule with known neuroprotective properties in lab and animal studies.
By the Numbers:
Why it matters: These findings lend support to an ongoing Phase 2a trial testing low-dose oral CO as a Parkinson's therapy. If proven effective, it could open a novel treatment avenue for a disease that currently has no cure.
