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Abstract:
In Parkinson's disease (PD), age of disease onset, and type
and lateralization of motor symptom at onset have been linked to
cognitive decline. Although these factors have been studied
independently, their relationship has not been fully explored. The
present study examined the impact of age of disease onset on
cognition in patients with different motor symptom profiles. We
administered a neuropsychological battery to 67 patients who
presented with either right-sided tremor (RSO-T), right-sided
bradykinesia/rigidity (RSO-B/R), left-sided tremor (LSO-T) and
left-sided bradykinesia/rigidity (LSO-B/R). Based on recent
findings showing RSO-T patients remain cognitively intact, we
predicted that age of onset would not present the same risk in this
patient group. Regression analyses demonstrated that older age of
onset predicted poorer performance on measures of fluency
(p<.001), verbal learning (p<.02) and memory (p<.001),
mental object assembly (p<.001), and mental flexibility
(p<.003) within the combined RSO-B/R, LSO-T, LSO-B/R group. Age
of disease onset did not predict performance within the RSO-T
group. These findings suggest that age of disease onset is a risk
factor for cognitive decline among patients who present with either
left-sided disease onset or bradykinesia/rigidity. A small subgroup
of patients, those who develop right-sided tremor, do not appear to
have an increased risk of developing neuropsychological impairment
when their disease presents later in life.
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