Hyposmia and cardiovascular dysautonomia correlatively appear in early-stage Parkinson's disease

Objective: Olfactory dysfunction is considered to precede motor symptoms and early markers of Parkinson's disease (PD), while the relative time at which cardiovascular dysautonomia appears in PD is not well understood. To assess the appearance of cardiovascular dysautonomia in PD, we evaluated its relation to olfactory dysfunction in early-stage PD patients. Methods: Twenty-three non-demented PD patients within 2 years from the onset of motor symptoms were enrolled. We evaluated olfactory dysfunction by the Odor Stick Identification Test for Japanese (OSIT-J) and analyzed its relationship to the results of other cardiovascular autonomic tests and cardiac ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy. Results: There was a correlation between olfactory scores and increased blood pressure in both the norepinephrine (r=0.75, p<0.0001, n=21) and dobutamine (r=0.57, p=0.0087, n=20) infusion tests and cardiac MIBG uptake (r=0.42, p=0.049, n=23). The fall in orthostatic blood pressure during the head-up tilt test was not correlated with the olfactory scores, but the Valsalva maneuver revealed that OSIT-J scores correlated with the pressure recovery time from phase III to the return of blood pressure to baseline (r=0.54, p=0.037, n=15) and with the magnitude of blood pressure overshoot during phase IV (r=0.67, p=0.0016, n=20). Conclusion: Our results demonstrate that extensive components of the cardiovascular sympathetic system as well as the olfactory system are correlatively impaired in the early stage of PD, suggesting that degeneration of broad aspects of the cardiovascular sympathetic system occurs concurrently with olfactory system degeneration during the premotor phase of PD.