Cognitive and Neuroanatomical Correlates in Early Versus Late Onset Parkinson's Disease Dementia

Background: Aging is the most important risk factor of development of dementia in Parkinson's disease (PD), but there are no data on clinical and radiological heterogeneity of PD dementia (PDD) depending on age at onset. Objectives: The goal of this study was to examine whether patients with PDD are clinically and radiologically heterogeneous depending on age at onset. Methods: A total of 116 patients with PD dementia and 121 age- and sex-matched normal controls were enrolled. The subjects were divided into early-onset (EOPDD; n = 39) and late-onset (LOPDD; n = 77) PDD with the respective age-matched control group based on a cutoff value of 70 years. The effects of diagnosis, age, and their interaction on neuropsychological tests, cortical thickness, and substantia innominata volume were assessed using analysis of covariance. Results: EOPDD patients had a poorer cognitive performance on digit backward, forward span test (p = 0.011 and 0.05), and visual recognition memory function (p = 0.012) compared with LOPDD patients. Additionally, EOPDD patients exhibited cortical thinning in the left anterior cingulate gyrus and the right inferior temporal gyrus, with significantly decreased normalized substantia innominata volume (p = 0.044). Conclusions: Our data demonstrated that EOPDD patients exhibit poorer cognitive performance and more severe atrophy in the cortex and substantia innominata, implying that EOPDD may be a distinct phenotype different from LOPDD.