Parkinson's disease affects about 3% of Americans over 65 years old. With an increasingly aging population, this percentage may grow. The symptoms of parkinsonism (tremor, gait disturbance, bradykinesia, and rigidity) occur in even more people, estimated to be 8 million over age 65. In a study that included very mild symptoms, parkinsonism occurred in about 15% of people 65 - 74 years of age, about 30% in those 75 - 84, and over half of people older than age 85.
Age
The average age of onset of Parkinson's disease is 55. About 10% of Parkinson's cases are in people younger than 40 years old. Older adults are at higher risk for both parkinsonism and Parkinson's disease. There is some evidence, however, that the risk declines significantly after age 75 and that the very elderly are at low risk.
Gender
Some research indicates that men may face up to twice the risk as women. Estrogen may offer some protection for women up until menopause. A 2001 study, for example, reported a higher rate of Parkinson's disease in women who had undergone hysterectomy. Other studies suggest that the disease also progresses more rapidly in men than women. Older women seem to be more at risk for gait disturbance and men for rigidity and tremor.
Family History of PD
People with siblings or parents who developed Parkinson's at a younger age are at higher risk for Parkinson's disease, but relatives of those who were elderly when they had the disease appear to have an average risk.
Ethnicity
African- and Asian-Americans appear to have a lower risk than Caucasians.
The Protective Effects of Nicotine and Coffee on Parkinson's Disease
Both smoking and coffee drinking have been associated with lower risk for PD. Researchers are trying to determine why these substances seem to protect against PD.
Smoking and Nicotine Replacement. Cigarette smokers appear to have a 40% lower risk for Parkinson's disease, indicating some protection by nicotine. This finding, of course, is no excuse to smoke, but such protection may help researchers develop new therapies. Studies on nicotine replacement have been few and have not provided any strong evidence that nicotine therapy provides benefits.
Coffee Consumption. Studies have indicated that the risk for PD in coffee drinkers is about 30% lower than for non-coffee drinkers. In a 30-year study of Japanese-American men, coffee consumption was associated with a lower risk for Parkinson's disease, and the more coffee they drank, the lower their risk became.
