Reduced sympathetically driven heart rate variability during sleep in Parkinson's disease: A case‐control polysomnography‐based study

OBJECTIVES: To study heart rate variability during nocturnal sleep in idiopathic Parkinson's disease. METHODS: Retrospective study, using part of the data set accumulated in an earlier study, in which polysomnography was performed in 35 idiopathic Parkinson's disease patients under their usual medication and in 35 non-idiopathic Parkinson's disease controls, matched for age, gender, and amount of apneas/hypopneas per hour. R-R intervals were calculated separately for non-rapid eye movements and rapid eye movements sleep stages. R-R variability was analyzed for time and frequency domains. Selected variables considered were high frequency band (0.15-0.40 Hz) influenced by parasympathetic input and low frequency band (0.04-0.15 Hz) influenced by sympathetic input. Both frequency bands were considered in normalized units (low frequency and high frequency normalized units). Low frequency/high frequency ratio was calculated as an estimate of sympathicovagal balance. RESULTS: All respiratory and sleep stage characteristics were similar in both groups. Low frequency normalized unit was reduced in idiopathic Parkinson's disease patients, both for non-rapid eye movements and rapid eye movements sleep (P = 0.005). Low frequency/high frequency was smaller in idiopathic Parkinson's disease for both sleep portions (P = 0.02). CONCLUSIONS: Idiopathic Parkinson's disease patients show reduced sympathetic influence on heart rate variability in both non-rapid eye movements and rapid eye movements sleep stages. We speculate that these findings are a consequence of the postganglionic noradrenergic cardiac denervation found in idiopathic Parkinson's disease patients.