Parkinson's (PD] and Alzheimer's (AD) diseases are age-related degener
ative disorders that share common clinical, pathological and biochemic
al features. Epidemiological studies show similiar age-specific incide
nce and prevalence curves, although PD tends to occur at earlier ages
and, at old age, AD is more frequent. Both diseases are more common in
western than in Mediterranean or Asiatic populations. These findings
suggest that these diseases may have common determinants.