Investigators in Sweden, Italy and the United States report that “non-smoking men who used snus had a substantially reduced risk of Parkinson’s disease.”
The research, published in the International Journal of Epidemiology, combined data from seven Swedish cohort studies involving nearly 350,000 men. Subjects were classified according to tobacco use and diagnosis of Parkinson’s disease (an illness of the nervous system affecting movement) over an average 16 years of follow-up.
The principal results are impressive:
Among never-tobacco smokers, Parkinson’s disease risk in ever-snus users was lower than in never-users (pooled [hazard ratio, similar to relative risk] HR = 0.41, 95 percent [confidence interval] CI 0.28-0.61, for the fully-adjusted model). Current-snus use was associated with a lower Parkinson’s disease risk than former use. In addition, there was evidence of dose-response relationships such that moderate-heavy amount (pooled HR 0.41, 95 percent CI 0.19-0.90) and long-term current-snus users (pooled HR 0.44, 95 percent CI 0.24-0.83) had the lowest Parkinson’s disease risks.
The bottom line: Current snus use, not former use, was strongly protective against Parkinson’s disease, with more protection from heavier and long-term use.
This is not the first such finding. In 2009, I discussed research from the American Cancer Society showing a similar strong protective effect (Relative risk, RR = 0.22, CI = 0.07 – 0.67). Further, Parkinson’s may not be the only nerve illness for which smokeless tobacco and/or nicotine use is protective. Snus users have a significantly lower risk for multiple sclerosis than nonusers of tobacco. Nicotine has been found to improve performance in people with mild cognitive impairment, and it may also benefit those with Alzheimer’s disease.
The current study represents a new era in Swedish snus research. It was conducted by the Swedish Collaboration on Health Effects of Snus Use, “which brought together Swedish prospective cohort studies with detailed information on tobacco smoking and snus use.”
In the past, the snus research field was dominated by investigators at the Karolinska Institute; they published a series of studies that featured obvious technical problems and contradictions, and routinely found significant, small risks. I documented these flawed studies in professional journals and on my blog (here, here, here, and here).
It is my hope that the Swedish Collaboration, with investigators from multiple universities in Sweden and beyond, will produce valuable, unbiased research on the health impact of snus use.
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