Reacción a "Exhaled carbon monoxide has been linked to a lower risk of Parkinson’s disease"

This is a very interesting observational study due to its scale – involving more than 500,000 adults aged between 30 and 79 who were followed for around 12 years – and, above all, because it offers a possible explanation for an association that we have been aware of for decades: smokers have a lower risk of developing Parkinson’s disease.

What is new is that the authors have directly measured exhaled carbon monoxide (CO) and found that, even amongst people who have never smoked, higher levels of CO are associated with a lower risk of Parkinson’s. This raises the possibility that the supposed protective effect of tobacco may be linked to CO and not necessarily to nicotine. It is an interesting hypothesis, moreover, because the potentially neuroprotective effects of CO had already been observed in experimental models.

The study is robust due to its large sample size, its prospective design and the objective measurement of CO, but caution is needed when interpreting the results. As this is an observational study, it demonstrates an association, not a causal relationship. Therefore, these results do not in any way imply that smoking is beneficial or that one should smoke to prevent Parkinson’s disease. Smoking remains a major cause of cancer, cardiovascular disease and mortality. Furthermore, the study participants are from the Chinese population, whose genetic and environmental characteristics, consumption habits, and patterns of exposure to smoke and pollution may differ from those of other populations. It is therefore prudent not to extrapolate these results directly to other populations until studies are available that replicate the association in different contexts.

From a clinical perspective, the most interesting aspect is that these results support research into the potential therapeutic use of very low, controlled doses of CO. This is a promising avenue, but it is still experimental and has no immediate clinical application.