Confirmed: Snus Use Protective for Parkinson’s Disease

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 (abstract here), 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% [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% CI 0.19-0.90) and long-term current-snus users (pooled HR 0.44, 95% 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 (here) research from the American Cancer Society showing a similar strong protective effect (Relative risk, RR = 0.22, CI = 0.07 – 0.67) (abstract here).  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 (here).  Nicotine has been found to improve performance in people with mild cognitive impairment, and it may also benefit those with Alzheimer’s disease (discussed here).

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 in 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.

Snus Nicotine Lowers Risk for Multiple Sclerosis, May be Therapeutic for Other Nerve Disorders

New research published in Multiple Sclerosis Journal (abstract here) and authored by Anna Hedström of Stockholm’s Karolinska Institute of Environmental Medicine confirms that snus users have a significantly lower risk for multiple sclerosis (MS) than nonusers of tobacco.  I discussed the researchers’ earlier findings on this subject five years ago in this blog (here).

Hedström’s study is based on some 7,900 Swedes with MS and 9,400 controls.  Compared with never users of tobacco, snus users had a lower risk for MS (odds ratio OR = 0.75, 95% confidence interval, CI= 0.63 – 0.90).  Hedström also showed an increased effect at higher duration-dose levels of snus.  For example, users with greater than ten packet-years (the number of snus doses per day and years of use) had an OR of 0.45 (CI= 028 – 0.68).  Smokers had modestly increased risk (OR= 1.49, CI= 1.40 – 1.59), a finding that is similar to that reported in Hedström’s previous study.

Scientific research is methodically unveiling the benefits of nicotine and smoke-free tobacco use with respect to degenerative brain diseases.  A finding that nicotine may improve performance in people with mild cognitive impairment (discussed here), has resulted in calls for more research on nicotine’s effect on dementia (reference here).

The impact of nicotine/tobacco use on Parkinson’s disease is well documented.  An American Cancer Society study (here) provides clear evidence that smokeless tobacco use may be protective for Parkinson’s disease (RR = 0.22, CI = 0.07 – 0.67).  In fact, nicotine is being discussed as therapy for this disorder (here, here  and here).

Alzheimer’s disease is the sixth leading cause of death in the United States, and Parkinson’s disease is the fourteenth.  The role of nicotine and smoke-free tobacco in reducing risk of or treating these disorders is of significant import.

Snus Use Lowers Risk for Multiple Sclerosis; Smoking Raises Risk

Multiple sclerosis (MS) is a chronic disease in which the immune system attacks and damages myelin, the substance that insulates nerves and facilitates transmission of electrical signals along the spinal cord, the mode by which the brain communicates with the rest of the body. It is a complicated disease, an excellent summary of which can be found here.

There are no definitive causes of MS; genetic and environmental factors may play a role. Several research studies indicate that smoking increases the risk for the disease by approximately 50% (RR = 1.5, 95% CI = 1.3 – 1.7).

Researchers at the Karolinska Institute of Environmental Medicine in Stockholm have just released a new study of tobacco use and MS, which was published in the September 1 issue of the journal Neurology. They compared tobacco use among persons diagnosed with MS (cases) with a group of controls derived from the Swedish population. This experimental design, called a population-based case-control study, is common in epidemiology.

Readers of this blog are familiar with relative risk (RR), which is used by some epidemiologic studies to measure the association of a risk factor and a disease. The measure of association in the present study was the odds ratio (OR), and its interpretation is essentially identical to the RR and is accompanied by a confidence interval (CI), which is the range within which the RR lies with 95% confidence.

Lead author Anna Hedström and her colleagues report that, compared with nonusers of tobacco, smokers had significantly elevated risks for MS. The OR for male smokers was 1.8 (CI = 1.3 – 2.5), and the OR for smoking women was 1.4 (CI = 1.2 – 1.7). The risk increased with the cumulative dose of smoking (measured in pack-years, that is, packs per day times years of smoking), which adds to the overall validity of the association. For example, compared to nonusers of tobacco, men who had up to 5 pack-years of smoking had an OR = 1.4 (CI = 1.0 – 2.0), while men who had 16+ pack-years of smoking had an OR = 2.9 (CI = 1.7 – 5.1).

In contrast to smoking, the study found that snus users had lower risks for MS than nonusers of tobacco. These lower risks were present among snus users of 5+ package-years who never smoked (OR = 0.4, not statistically significant) and who had smoked (OR = 0.3, CI = 0.1 – 0.9), the latter being statistically significant.

A previous study by the American Cancer Society showed that smokeless tobacco use may be protective for Parkinson’s Disease (a neurologic illness) (RR = 0.22, CI = 0.07 – 0.67). The Karolinska Institute study provides evidence that smokeless tobacco may provide protection for multiple sclerosis as well.