Autonomic dysfunction in Parkinson's Disease: an evaluation of acute and chronic effects of cognition and daily life
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Non-motor symptoms of Parkinson's disease (PD) have emerged as an important research topic. Autonomic dysfunction is particularly prevalent, with the most common manifestation being orthostatic hypotension (OH). While cognitive deficits have been demonstrated in PD even in the absence of dementia, there has been no investigation of the potential effects of hemodynamic disorders on cognitive performance. The main hypothesis of the present study was that PD patients with OH would be cognitively impaired relative to those without OH, especially when in the upright position. The effects of impaired postural hemodynamics on cognition were examined in 36 nondemented PD patients - 18 diagnosed with OH (PDOH) and 18 without OH (PDNOH) - and 18 healthy normotensive control participants (NC) matched for age, male:female distribution, and education. Neuropsychological measures of executive function, visuospatial performance, memory, and attention/concentration were repeated in supine and upright positions to evaluate chronic and acute hemodynamic effects, respectively. Autonomic measures, taken concurrent to neuropsychological testing, included beat-to-beat arterial pressure, electrocardiography, transcranial Doppler sonography, and respiratory function. The first study assessed cognition associated with a diagnosis of OH. The second examined the relation between changes in blood pressure and cerebral blood flow and the impact of impaired hemodynamics on cognition. The third assessed the relation between subjective autonomic complaints and measurable impairments in autonomies and cognition. As hypothesized, both PDNOH and PDOH were impaired relative to NC, regardless of posture. There were few chronic effects of OH on cognition (PDNOH vs. PDOH, supine) whereas PDOH were significantly more impaired than PDNOH when upright (acute effect). Cerebral blood flow was reduced in PDOH compared to PDNOH and NC, and this reduction was correlated with performance on cognitive tests. PDOH had more subjective autonomic and functional complaints than PD alone. The presentation of PD with comorbid OH is associated with cognitive impairment, particularly while in the upright position, in patients without dementia. The prevalence of comorbidity of OH in PD is significant. The accompanying cognitive deficiency indicates that OH should be treated as both a physiologically dangerous and neuropsychologically relevant issue in individuals with this disorder.
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