Study design and participants
The subjects were 75 de novo PD patients who were diagnosed using the criteria for PD proposed by the UK Parkinson’s Disease Society Brain Bank [16], and 24 de novo DLB patients with a central feature and two or more core features in diagnostic criteria, which is sufficient for diagnosis of probable DLB [17]. All patients were examined at Disan Hospital, The Jikei University School of Medicine, between January 2012 and March 2018, and were diagnosed by at least two neurologists. We also used a 1-year rule to distinguish DLB from PD with dementia [17].
Patients with overt diabetes or clinically relevant cardiac disease, and those who had been treated with tricyclic antidepressants, tetracyclic antidepressants, serotonin reuptake inhibitors, and serotonin and norepinephrine reuptake inhibitors were excluded from the study. None of the patients had received levodopa, other anti-Parkinson drugs, or treatment for OH. Global cognition and executive function were evaluated using the MMSE and the Frontal Assessment Battery (FAB). No patient had atrophy on brain MRI of the putamen, brainstem or cerebellum. If patients were already receiving antihypertensive drugs, such drugs were withdrawn at least 48 hours before evaluation of OH. All patients received levodopa or a dopamine agonist for their parkinsonism after this study, and all had a good response.
The motor severity of PD was assessed using the Unified Parkinson’s Disease Rating Scale (UPDRS) motor score. The patients were divided into tremor-dominant, akinetic-rigid, and mixed type subgroups based on the tremor and non-tremor scores, which were obtained using part III of the UPDRS [18]. This study was approved by the Ethics Committee of The Jikei University School of Medicine, and all subjects gave written informed consent before enrollment.
Cardiac 123I-metaiodobenzylguanidine (MIBG) scintigraphy
Cardiac sympathetic denervation was evaluated using MIBG scintigraphy. The ratio of the average pixel count in the heart (H) to that in the mediastinum (M) (H/M ratio) at 15 min (early) and 3 hours (delayed) after injection of 111 MBq 123I-MIBG (Fujifilm RI Pharma Co., Ltd. Tokyo, Japan) was calculated [19].
Olfactory assessment
Olfactory function was assessed by the odor stick identification test Japan (OSIT-J) (Daiichi Yakuhin Sangyo Co. Ltd., Tokyo, Japan), as described in our previous study [20] . The number of correct responses for the 12 odorants was defined as the OSIT-J score, which has been shown to be significantly correlated with those on the University of Pennsylvania Smell Identification Test (UPSIT) and the cross-cultural, smell identification test (CC-SIT) [21, 22].
Head-up tilt-table test (HUT)
All subjects underwent HUT in a silent room maintained at an ambient temperature of 23 to 26°C. After an overnight fast, the test was started at 9:00 am. After resting for 20 min in the supine position, the subject was tilted to a 60° upright position for 3 min. Brachial systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured by an automated sphygmomanometer after 20 min of rest in the supine position and every 1 min after the subject was tilted for up to 3 min. The maximum decreases in SBP and DBP during tilt were evaluated. Plasma norepinephrine concentrations in serum (NE, μg/ml)) were measured with the subjects in a supine position after 20 minutes of rest and after 10 min in a tilted position. OH was defined as a fall in SBP by ≥20 mmHg [23]. Supine hypertension (SH) was defined as SBP >140 mmHg or DBP >90 mmHg, as measured after 20 min of rest in the supine position [24]. Neurogenic SH was defined as a case of OH with SBP >140 mmHg or DBP >90 mmHg in the supine position [25].
24-hour ambulatory blood pressure monitoring (ABPM)
24-hour ABPM was performed using a noninvasive automated portable recorder in hospitalized patients and outpatients. BP was measured every 30 min during the day (7:00-21:00) and every hour at night (22:00-6:00). SBP was used as an indicator of BP. The nocturnal fall in BP was calculated as: SBPday – SBPnight/SBP day × 100 (%), where SBPday is the mean SBP during the day, and SBPnight is the mean SBP at night. Cases with nocturnal falls in BP of ≥10%, <10% and no fall were defined as dipper, non-dipper, and riser types [26, 27].
75-g oral glucose tolerance test for evaluation of postprandial hypotension
After overnight fasting (except for non-caloric liquids), the 75-g OGTT was started between 9:00 and 10:00 am in a quiet room at an ambient temperature of 23 to 26°. Whenever possible, we performed HUT followed by the 75-g OGTT on the same day. If this was not possible, the 75-g OGTT was performed on the day after HUT. After 20 min resting in the supine position, the subjects drank 75 g of glucose water (calorie content, 300 kcal) and remained resting and awake in the supine position for 120 min. After 20 min and then every 10 min for the next 120 min, brachial SBP and DBP were measured by an automated sphygmomanometer in the supine position. The time to the maximum drop in SBP on the 75-g OGTT was measured. Postprandial hypotension (PPH) was defined as a maximum decrease in SBP of 20 mmHg within 2 hours after glucose intake [28, 29].
Constipation
Constipation was defined as the presence of at least one of two criteria: absence of daily defecation, and use of drugs to treat constipation [30].
Statistical analysis
Statistical analyses were performed with statistical software (Esumi Co., Ltd., Tokyo, Japan). Differences between groups were compared by Wilcoxon rank sum test for continuous variables. Pairwise comparisons were made using χ2 tests for binary variables. Lepage analysis was used to evaluate differences in nocturnal fall in BP. Associations of MMSE and FAB scores with clinical factors such as age, gender, symptom duration, UPDRS motor score, motor subtype, olfaction, cardiac MIBG uptake, BP fall in HUT, NE at rest in the supine position in HUT, nocturnal fall in BP in ABPM, PPH, SH and constipation were evaluated by multiple regression analysis. P<0.05 was considered to indicate significance.