Apolipoprotein E ε4 Allele Does Not Influence the Development of Dementia in Parkinsonian Patients

James Parkinson in 1817 in his famous Essay on the Shaking Palsy described the “involuntary tremulous motion, with lessened muscular power, in parts not in action and even when supported; with a propensity to bend the trunk forwards, and to pass from a walking to a running pace: the senses and intellects being uninjured” (Parkinson, 1817). Indeed the possibility that PD is associated with dementia has been negated by neurologists for several decades. It should be mentioned that antedating levodopa therapy patients could not be formally cognitively tested because of their motor disability, bradyphrenia and speech impairment. There was also a tendency to attribute dementia in old age (and the great majority of PD patients are aged) to concurrent “senility” or “cerebral aterosclerosis” Once levodopa and dopa-agonist therapy was instituted this situation, surprisingly, did not change and the impression emerged that dementia is common in PD, more so in patients with advanced PD (Korczyn et al., 1986). Since then, overwhelming proof has accumulated that PD is accompanied by dementia in at least 20% of the cases. The debate over the issue of coincidental AD in demented PD patients is still not entirely resolved since some of the clinical and pathological features of the two dementias are similar.