| OBSERVATION'S |
Parkinson's disease is unusual because its incidence seems to be decreased by a person's use of tobacco, caffeine, and alcohol. The strongest preventive agent seems to be tobacco. According to G. Webster Ross, a researcher at the Parkinson's Institute, more than 35 epidemiological studies have consistently demonstrated an inverse association between years of smoking and risk of Parkinson's. This inverse association "is reported for every continent and every race," he said. "The odds ratios, in these studies, cluster around 0.5," he said, which means that smokers have about half the risk of contracting Parkinson's as nonsmokers. One possible explanation for this phenomenon is that nicotine stimulates the release of dopamine in the striatum. In laboratory animals with lesioned pathways in the substantia nigra, nicotine preserves striatal dopamine levels
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