Reduced sympathetic activity in idiopathic rapid-eye-movement sleep behavior disorder and Parkinson's disease

BackgroundMore than 50% of patients with idiopathic REM sleep behavior disorder (iRBD) will develop Parkinson's disease or Lewy body dementia. In a previous study, we found attenuated heart rate responses in iRBD and Parkinson's disease patients during sleep. The current study aimed to evaluate heart rate variability further in order to identify possible changes in these components during wakefulness and sleep in patients with iRBD and Parkinson's disease.MethodsWe evaluated heart rate variability in 5-minute electrocardiography segments from wakefulness, and non-REM and REM sleep in 11 iRBD patients and 23 Parkinson's disease patients, and compared these with 10 control subjects.Results and conclusionsPatients with iRBD had attenuated sympathetic nervous system activity compared with controls and this was more pronounced in patients with Parkinson's disease. The cardiac parasympathetic nervous system seems to be relatively well preserved in patients with iRBD and Parkinson's disease. The progressive reduction of sympathetic nervous activity is in line with the postganglionic sympathetic nervous dysfunction seen in early Parkinson's disease.