) - Relatives of patients with Parkinson's disease appear to be at
increased risk for impaired thinking and dementia, suggesting the
presence of shared susceptibility factors, new research indicates.
Whether these factors are genetic or whether they relate to a shared
lifestyle will require further study.

The association is primarily seen among families of patients who are
younger when the develop Parkinson's disease, "but the risk does not
vary across relatives of patients with different (symptoms) of
Parkinson's disease," Dr. Walter A. Rocca, from the Mayo Clinic
College of Medicine in Rochester, Minnesota, and colleagues report
in the Archives of Neurology.

Rocca's team conducted a study involving 1019 first-degree relatives
of 162 Parkinson's disease patients and 858 relatives of 147 similar
subjects without the disease. Thinking ability was measured via
telephone questionnaire or, in demented subjects, by interviewing
close associates. In addition, the medical records of demented
subjects were reviewed to confirm the diagnosis.

Relatives of Parkinson's disease patients were 37 percent more
likely to show thinking deficits or dementia than were relatives of
unaffected subjects, the report indicates.

As noted, the heightened risk in relatives was most apparent if
Parkinson's disease developed at 66 years of age or younger.
Relatives of patients with Parkinson's at a younger age were 73
percent more likely to have thinking impairments or dementia than
were relative of unaffected subjects.

To confirm their findings, the researchers also examined the risk of
thinking impairments in 2,716 first-degree relatives of 411
Parkinson's disease patients referred to the Mayo Clinic. This
analysis showed that the association was confined to relatives of
patients with younger age at onset.

SOURCE: Archives of Neurology, October 2007.

Date updated: October 08, 2007
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