Relatives of Parkinson Disease Patients
Face Increased Risk of Cognitive Impairment

First-degree relatives of patients with Parkinson disease face greater risk of developing cognitive impairment or dementia than people who have no first-degree relatives (brother, sister, mother, father, son, or daughter) with Parkinson disease, according to a new study by Mayo Clinic investigators. The risk is particularly increased for relatives of patients who developed Parkinson disease before the age of 67 years.

The Mayo Clinic report appeared in the October 2007 issue of the journal Archives of Neurology. It is one of the first large population-based studies to show that Parkinson disease and cognitive impairment or dementia may share familial susceptibility factors that make a person prone to developing one or both disorders. Results emphasize the clinical importance of taking careful family medical histories to accurately assess the risk of Parkinson disease a patient may face.

The study is based on the family study method, in which researchers assessed each relative separately for cognitive status instead of using only 1 family member to provide information for the full family.

The Mayo Clinic team studied

• 1,019 first-degree relatives of 162 patients with Parkinson disease from Olmsted County, Minnesota
• 858 first-degree relatives of 147 matched healthy controls from the same geographic area
• 2,716 first-degree relatives of 411 patients with Parkinson disease who were referred to Mayo Clinic from a broader area, including Minnesota, Iowa, Wisconsin, North Dakota, and South Dakota

Researchers emphasize that the familial susceptibility factors may be genetic or nongenetic, such as shared diet in the family. Further research is needed to determine susceptibility factors.