Clinico-imaging features of subjects at risk of Lewy body disease in NaT-PROBE baseline analysis – npj Parkinson’s Disease

Ethics approval

This study was conducted in accordance with the 1964 Declaration of Helsinki and its later amendments, the Ethics Guidelines for Human Genome/Gene Analysis Research, and the Ethical Guidelines for Medical and Health Research Involving Human Subjects endorsed by the Japanese government. The study protocol was approved by the Ethics Review Committee of Nagoya University Graduate School of Medicine (No. 2017-0521). All participants provided their written informed consent before participation in the study.

Participants

The Nagoya-Takayama preclinical/prodromal Lewy body disease study (NaT-PROBE study) is a prospective, longitudinal, multi-center, community-based cohort study coordinated by Nagoya University School of Medicine¹⁶. Since March 2017, we have been conducting a survey of prodromal symptoms in healthy individuals who visited Kumiai Kosei Hospital or Daido Clinic, Japan, for their annual health checkup. In Japan, regular medical checkups, which are obligatory for employees, are performed annually according to the Industrial Safety and Health Law. We used health checkup cohorts in Kumiai Kosei Hospital and Daido Clinic to screen for prodromal symptoms in the Japanese community-based population by using the following questionnaires: the Japanese version of the Scale for Outcomes in Parkinson’s disease for Autonomic Symptoms (SCOPA-AUT); the Self-administered Odor Question (SAOQ); the RBD screening scale (RBDSQ); the Beck Depression Inventory-Second Edition (BDI-II); the Epworth Sleepiness Scale (ESS); and the Physical Activity Scale for the Elderly (PASE). Based on the results of our previous study¹⁶, we classified subjects who were ≥50 years old and had ≥2 abnormal scores in the SCOPA-AUT, SAOQ, and RBDSQ into the high-risk group. The cut-off value for identifying the high-risk group was 10 for SCOPA-AUT, 90.0% for SAOQ, and 5 for RBDSQ¹⁶. Subjects who were ≥50 years old and had no abnormalities in any of the questionnaires were classified into the low-risk group.

Between April 2018 and March 2021, we sent invitations to undergo neurological and imaging examinations for LBD to 341 high-risk and 169 low-risk individuals who were identified in the NaT-PROBE study. On the high-risk and low-risk subjects who gave written consent for the present study, we performed a detailed examination of the motor, cognitive, and physiological functions, non-motor symptoms, and DaT-SPECT and cardiac MIBG scintigraphy. All the examinations for both low- and high-risk groups were performed for solely research purposes with the funds supporting this study.

We excluded participants who had PD or DLB at the baseline assessment. In addition, participants with a history of psychiatric or neurological disorders other than depression and those with brain MRI abnormalities were also excluded from this study. Serum, plasma, and urine samples were collected from all participants for future research use.

Motor and cognitive examinations

The Movement Disorder Society-sponsored revision of the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) was scored by neurologists who were certified as MDS-UPDRS evaluators (M.H., Y.S., K.H. and K.Y.) for assessing motor and non-motor symptoms related to PD. The Japanese version of the Montreal Cognitive Assessment (MoCA-J) was administered to assess the general cognitive function, the Stroop test and trail making test were conducted to assess the frontal lobe function, and the line orientation test and pareidolia test were conducted to assess the visuospatial cognitive function.

Physiological function tests

We conducted the Odor Stick Identification Test for Japanese (OSIT-J) to assess objective olfactory dysfunction. The OSIT-J is a stick-type olfaction test, consisting of 12 odorants typically familiar to Japanese subjects, and is a simple test that takes approximately 10 min to complete²¹. The CVRR was measured as previously described²². In brief, participants maintained a supine position with normal breathing for more than 5 min. The resting-CVRR was calculated as a percentage of the standard deviation of the last 100 R-R intervals divided by their mean. To assess the deep breath-CVRR, participants took 12 deep breaths over a 2-min period, and the deep breath-CVRR was calculated using the first 100 successive electrocardiogram R-R intervals.

Imaging tests

We conducted DaT-SPECT imaging with [123I]FP-CIT to detect presynaptic dopamine neuronal dysfunction. All patients were scanned at Nagoya University Hospital or Kumiai Kosei Hospital. DaT-SPECT data were acquired using a Symbia T (Siemens, Erlangen, Germany), equipped with a low-medium energy general-purpose (LMEGP) collimator at Nagoya University Hospital, and an Infinia (GE Healthcare, Milwaukee, WI, USA), equipped with a low-energy high-resolution (LEHR) collimator at Kumiai Kosei Hospital. Ninety projections over 360° orbit with 2 detectors were acquired on a 128 × 128 matrix (zoom factor, 1.45), giving a pixel size of 3.3 mm and acquisition time of 28 min. The main energy window was 159 keV±10%, and 2 subwindows were set at 8% at both ends of the main window. Images were reconstructed using a three-dimensional ordered subset expectation maximization method (3D-OSEM) (iteration, 6; subset, 8) and Gaussian filter full width at half maximum (FWHM) 6 mm with attenuation correction (AC) by computed tomography (CT) and scatter correction (SC) using the triple energy window method²³ in the same way as in a recent Japanese study²⁴ on DaT-SPECT. The specific binding ratio (SBR) values were obtained for both the right and left striatum regions. The Southampton method is widely used in Japan and uses a large volume of interest (VOI), including the entire striatum, to correct the partial-volume effect (PVE)²⁵. The SPECT count density computed by this method was defined as CSouthampton. We used the software program DaTView (AZE, Tokyo, Japan), which adopted the Southampton method to compute the CSouthampton for the left and right striatum and BG regions. We defined the most affected striatum side as the ‘lower side’ and the opposite side as the ‘higher side’ with SBR values. We used the average of the right and left sides as the SBR ‘average’. The asymmetry index of SBR was calculated using the following equation: asymmetry index [%] = (SBR_{predominantly affected} – SBR_{less affected}) × 2/(SBR_{predominantly affected} + SBR_{less affected}) × 100^25,26. The decrease in SBR was evaluated in reference to the values of Japanese volunteers²⁷.

Cardiac [¹²³I]MIBG scintigraphy (123I-MIBG) was performed to assess postganglionic cardiac autonomic denervation. MIBG (111 mBq) was injected intravenously into the participants. Early images were obtained 15 min after the injection, and delayed images were obtained after 4 h. The myocardial MIBG uptake was measured using the heart-to-mediastinum ratio (H/M ratio) according to methods described previously²². None of our patients had taken drugs known to affect the MIBG uptake (e.g. tricyclic antidepressants, Ca²⁺ blockers, or selegiline). Normal values for myocardial MIBG scintigraphy are ≥2.2 for the early H/M ratio, ≥2.2 for the delayed H/M ratio, and ≤34% for the washout rate²⁸.

Questionnaires on motor and non-motor symptoms

We used the PASE to evaluate the amount of physical activity, the Japanese version of the SCOPA-AUT to evaluate autonomic dysfunction, the SAOQ to evaluate olfactory dysfunction, the RBDSQ to evaluate RBD, the BDI-II to evaluate depressive symptoms, the ESS to evaluate excessive daytime sleepiness, the Parkinson’s Disease Questionnaire-39 (PDQ-39) to evaluate the PD-specific health-related quality of life, and the Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease (QUIP) to evaluate impulse control disorder.

All scales used in this study were validated for self-administration in a Japanese population^{20,29,30,31,32,33,34,35}.

Statistical analyses

All data represent the mean±standard deviation unless otherwise stated. The demographic and clinical scores of the high-risk and low-risk groups were compared using Student’s t-test or the Mann–Whitney U-test when appropriate. Fisher’s exact test was used to compare categorical variables between groups, and Bonferroni correction was used to calculate adjusted p-values for multiple comparisons. For the comparisons among the high-risk subjects with and without abnormal DaT-SPECT and/or MIBG, a parametric one-way analysis of variance (ANOVA) followed by Dunnett tests or non-parametric Kruskal–Wallis tests followed by Steel tests were performed. For the comparison of the high-risk subjects with and without DaT-SPECT and MIBG abnormalities, the analysis was performed after adjusting for age with an analysis of covariance (ANCOVA). Pearson’s correlation coefficient was used to determine the relationships between each clinical score and the DaT-SPECT SBR or delayed MIBG H/M ratio.

P-values of <0.05 were considered to indicate statistical significance. Correlation coefficients (r) were interpreted as follows: >0.8, very strong; 0.5–0.8, moderately strong; and 0.3–0.5, weak. All statistical analyses were conducted using EZR (Saitama Medical Center, Jichi Medical University, Saitama, Japan)³⁶, which is a graphical user interface for R (The R Foundation for Statistical Computing, Vienna, Austria).

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.