Patients with Parkinson’s disease can quit smoking more easily than healthy individuals can, according to data published October 14 in Neurology. A decreased responsiveness to nicotine during the prodromal phase of Parkinson’s disease may account for these findings.
The authors hypothesized that “ease of smoking cessation is an aspect of premanifest Parkinson’s disease similar to olfactory dysfunction, REM sleep disorders, or constipation.” The apparent neuroprotective effect of smoking observed in previous epidemiologic studies may result from reverse causation, they added.
Beate Ritz, MD, PhD, Professor and Vice Chair of the Epidemiology Department at the University of California, Los Angeles, and colleagues conducted a case–control study to investigate the relationship between smoking and Parkinson’s disease. The researchers examined the Danish National Hospital Register and identified 1,808 patients with Parkinson’s disease who had been diagnosed between 1996 and 2009. Using the Danish Central Population Registry, Dr. Ritz’s group matched the patients with 1,876 population controls regarding sex and year of birth. Through telephone interviews, the investigators obtained information on demographics, education, and lifestyle habits, including lifelong smoking history and use of nicotine substitutes.
Patients with Parkinson’s disease were less likely to ever smoke cigarettes, and associations were strongest for current smokers, followed by former smokers. Former smokers who said that it was “extremely difficult to quit smoking” had a 31% decreased risk of developing Parkinson’s disease, compared with individuals who reported that “quitting was easy.”
Approximately 3% of cases and 5% of controls reported ever using nicotine substitutes. Participants who had ever used nicotine substitutes had a reduced risk of Parkinson’s disease. The use of nicotine substitutes was strongly associated with quitting difficulty and heavy smoking.
“We find a strong association between smoking and Parkinson’s disease, and a trend in risk with increasing smoking duration,” said Dr. Ritz. “These observations suggest that a mechanism associated with Parkinson’s disease risk may influence smoking behavior or that less reward from nicotinic stimulation might be an event prodromal to Parkinson’s disease,” she added.
The study results indicate that “practicing neurologists should not recommend cigarette use or nicotine substitutes to delay the onset of Parkinson’s disease,” said Linda A. Hershey, MD, PhD, Professor of Neurology at the University of Oklahoma Health Sciences Center in Oklahoma City, and Joel S. Perlmutter, MD, Head of the Movement Disorders Section at Washington University in St. Louis, in an accompanying editorial. “Physicians, including neurologists, should encourage their patients to stop smoking because cigarette smoking is a significant risk factor for stroke,” they concluded.