ROCHESTER, MINNESOTA. Parkinsonism is a common neurodegenerative disease; its main symptom being a pronounced tremor affecting the extremities notably the hands, chin or lips. Other characteristic symptoms are stiffness or slowness of movement, a shuffling walk, stooped posture, and difficulties in performing simple tasks. Parkinsonism can be caused by pharmaceutical drugs such as reserpine, chlorpromazine, and verapamil. It is also a common feature in dementia. However, the majority of parkinsonism patients suffer from Parkinson's disease which is parkinsonism of unknown cause (idiopathic). Researchers at the Mayo Clinic have just released the results of a 15- year study aimed at determining the incidence of the various types of parkinsonism in a representative sample of residents in Olmsted County. During the period 1976 through 1990 the researchers documented 364 cases of parkinsonism. Most of these (42 per cent) were classified as Parkinson's disease, but an astounding 20 per cent was deemed to have been caused by poisoning by pharmaceutical drugs. The incidence of drug- induced parkinsonism was particularly high among women where it accounted for 28 per cent of all cases. Drug-induced parkinsonism is often reversible by prompt withdrawal of the offending drug. Parkinsonism associated with dementia was the most common form among old men (80-99 years of age) where it accounted for 41 per cent of all cases. The incidence of parkinsonism was found to rise dramatically with age from 26.5 cases per 100,000 person years in the 50-59 year age group to 304.8 per 100,000 in the age group 80-99 years. Overall the cumulative risk of developing parkinsonism by age 90 was found to be 7.5 per cent.
Bower, James H., et al. Incidence and distribution of parkinsonism in Olmsted County, Minnesota, 1976-1990. Neurology, Vol. 52, April 12, 1999, pp. 1214-20