Nicotine was long thought to fuel the inverse relationship between smoking and Parkinson's disease.In this study, nonsmokers with high carbon monoxide (CO) levels had less Parkinson's risk, suggesting CO may underlie smoking's neuroprotective effects.The study followed more than 500,000 people for 12 years, measuring exhaled CO at baseline.
Non-smokers with higher exhaled carbon monoxide (CO) levels had a lower risk of Parkinson's disease, a prospective study of more than 500,000 people in China showed.
Among people who never smoked, exhaled CO levels of 3 ppm or greater were associated with an approximately 30% lower risk of Parkinson's (HR 0.71, 95% CI 0.59-0.84) compared with exhaled levels under 3 ppm, reported Andri Iona, DPhil, of the Nuffield Department of Population Health at the University of Oxford in England, and co-authors.
Regular smoking also was tied to a reduced risk of Parkinson's disease (HR 0.70, 95% CI 0.62-0.79) but unlike CO measurements, was significantly associated with higher risks of lung cancer, ischemic heart disease, stroke, and all-cause mortality, the researchers wrote in JAMA Neurology.
"For the first time, this study provides robust evidence in humans supporting a potentially protective role for CO in Parkinson's," co-author Clara Bueno Lopez, MSc, also of Oxford, told MedPage Today.
