FREE RECALL AS A FUNCTION OF AGE OF ONSET, MEDICATIONS, AND DEPRESSION IN PARKINSON'S DISEASE.

Abstract

Thirty-two parkinsonians were compared to 32 age-, sex-, and education-matched healthy controls on measures of depression (Beck Inventory), dementia (Mattis Dementia Rating Scale), and primary and secondary memory components of Free Verbal Recall. Parkinsonians were found to be more depressed, with greater impairment of secondary memory. There were no significant group differences in primary memory or general cognitive functioning. Sub-groups of 41 parkinsonians (including the 32 patients described above) were used to compare the relative contributions of depression, age of onset, and general cognitive decline to the observed secondary memory deficit. Depressed parkinsonians demonstrated more impaired primary memory than did nondepressed parkinsonians, but did not account for the difference in secondary memory. Parkinsonians with later ages of onset demonstrated greater depression and cognitive decline over a shorter length of illness, and parkinsonians with greater cognitive decline performed more poorly on the measure of secondary memory. Comparisons of parkinsonians with predominant unilateral motor symptoms (either right or left) to those with equal bilateral symptoms revealed the bilateral group to be significantly older, with later ages of onset but no difference in length of illness. It is concluded that later age of onset is a critical factor that is more likely to be associated with depression and declines in cognitive functioning than is seen with earlier age of onset. The relationship between age of onset and cognitive decline is not accounted for by age alone, length of illness, nor by the interaction of age with parkinsonian symptoms. Furthermore, the presence of bilateral symptoms may serve as a marker for the cluster of symptoms associated with later ages of symptoms onset.