[Parkinson's disease and smoking: coherence and plausibility]

Many studies have shown that smoking is lower in patients with Parkinson s disease. However, in other investigations this was not observed. The various studies involved showed wide variation with regard to methodology, criteria for diagnosis and periods of observation and hence it is difficult to compare them.

The first studies published were designed to examine the effects of smoking in general and information was obtained regarding the possible disorders related to tobacco smoking according to the records of mortality, which may contain errors due to selective mortality and mistaken diagnosis. Most of the studies of cases and controls included prevalent cases which accepted the study, mainly hospital cases. Also it is probable that the prevalent cases of Parkinson s disease do not smoke because of their disorders of movement.

Many researchers have found important information about the pathophysiology of Parkinson s disease and its association with smoking. However, the hypothesis regarding the association between smoking and low risk of Parkinson s disease are various and independent, apart from the hypothesis of a truly biological mechanisms. Since the subject is still controversial, systematic reviews together with epidemiological and experimental studies are necessary.