Epidemiology of Parkinson's Disease: The Rotterdam Study

At present, Parkinson's disease (PO), after Alzheimer's disease, is generally considered to be the most frequent progressive neurodegenerative disease in the elderly. Due to the growing proportion of elderly in many populations, more and more persons will be affected by this disabling disease which constitutes a large burden to man and society. Since the publication of James Parkinson's essay, almost two centuries have elapsed and, in spite of numerous efforts to unravel the nature of the disease, the etiology of PO is still unknown. Yet, the neuropathologic and biochemical changes that cause the signs of the disease seem to be settled, based on knowledge that was mainly accumulated in only the past three decades. Neuropathologically, PO is defined by selective degeneration of pigmented neurons of the pars compacta of the substantia nigra and other brainstem ganglia, with cytoplasmic inclusions, called Lewy bodies, in the surviving neurons as the hallmark. These lesions lead to a deficiency of striatal dopamine. It is now considered that parkinsonian signs only become clinically overt after dopaminergic cell loss of approximately 50% and that at that moment the endogeneous dopamine content is depleted by 80%.