The Institute of Statistical Mathematics

Abstract SSEs are closely linked to megathrust earthquakes, as they occur near seismically locked zones and can perturb stress conditions along plate boundaries. Understanding their timing is, therefore, crucial for assessing seismic hazards. This study investigates the recurrence intervals of slow slip events (SSEs) at four regions in Japan: Kii peninsula, Yaeyama islands, Boso peninsula, and Bungo Channel. Using renewal processes based on the Brownian Passage Time (BPT) model and the Gamma model as well as the moment method, the study estimates the mean recurrence intervals and their coefficients of variation (the standard deviation divided by the mean) along with the estimation uncertainties in each region. Final estimated mean recurrence intervals are 0.96 years (Kii), 0.51 years (Yaeyama), 3.97 years (Boso), and 3.16 years (Bungo) for all methods. Coefficients of variation reflecting event periodicity in the four regions (0.42−0.46, 0.25−0.40, 0.44−0.54, 0.26−0.28) suggest that SSEs are quasi-periodic, being neither completely deterministic nor highly random. Compared to earthquakes with recurrent patterns of occurrence, which are typically less sensitive to small stress changes, SSEs generally exhibit higher variability in the recurrence, suggesting greater sensitivity to external perturbations. However, Bungo SSEs, with higher stress drops, exhibit lower variability, indicating more stable recurrence. The bootstrap analysis also confirmed regional characteristics. In Kii, SSEs occurring at the intermediate area, with the distance from the Nankai Trough axis to the fault center is approximately 25–36 km, show greater timing variability. In Yaeyama, recurrence appears linked to slip size, suggesting time-predictable behavior. In Boso, the 2011 Tohoku–Oki earthquake likely influenced SSE timing. In Bungo, the unique 2014 SSE, possibly affected by the Tohoku–Oki event, was highlighted. In addition, the study performs predictive model comparisons for the baseline renewal process and a retrospective predictability analysis for all the regions, and provides forecasts of the next SSE in the Kii region along with prediction intervals for its occurrence time.

This cross-sectional study explored outcomes in patients with cancer following opioid initiation (maximum observation period: 6 months), based on an analysis of laxative prescription patterns for opioid-induced constipation (OIC) using the Medical Data Vision Co., Ltd., a nationwide acute care hospital claims database in Japan. Of 26,939 patients included, 16,214 (60.2%) developed OIC, defined as the prescription of a laxative on or after the fourth day following the initiation of opioid therapy. At baseline, the average age was 69.3 years, with 58.0% being male patients. Overall, 42.7% of patients were hospitalized at the time of opioid initiation (OIC subgroup: 51.1%; non-OIC subgroup: 30.1%). The majority of patients (53.9%) had observation data for less than 6 months (OIC subgroup: 61.8%; non-OIC subgroup: 42.0%). Although there were disparities in patient backgrounds and observation periods, the total healthcare costs incurred were approximately ¥2,400,000, with ¥2,800,000 in the OIC subgroup and ¥1,800,000 in the non-OIC subgroup. Overall, these results highlight the importance of implementing appropriate OIC management strategies in Japan. However, it is noteworthy that the sequence of events between OIC onset and clinical outcomes remains unclear.

Depression is a leading cause of global disability, and subthreshold cases contribute substantially to the burden. Cognitive behavioural therapy (CBT) is effective for depressive symptoms, but its impact on social functioning in subthreshold depression remains unclear. This study evaluated the effects of smartphone-based CBT on social functioning and personal health records among individuals with subthreshold depression and examined whether a personalised and optimised therapy (POT) algorithm enhanced these outcomes. We performed a secondary analysis of the RESiLIENT trial (n=5361). Participants were stratified by baseline Patient Health Questionnaire-9 (PHQ-9) scores (0-4 and 5-14) and randomised to nine CBT app groups or a self-check group. Outcomes included social functioning and health records. A mixed-effects model for repeated measures was used to analyse the outcomes. The POT algorithm selected CBT skills tailored to individual characteristics. Depressive symptoms improved in both PHQ-9 groups compared with those of the self-check group, but gains in social functioning were modest, observed mainly in the PHQ-9 score ≤4 group. No consistent benefits were seen for health behaviours, job resignation, sick leave or healthcare costs. However, in a simulated randomised comparison using 10-fold cross-validated datasets, the POT algorithm had potentially beneficial effects for productivity (standardised mean difference (SMD)=0.16, 95% CI 0.03 to 0.29) and social adjustment (SMD=-0.13, 95% CI -0.26 to 0.00). Smartphone CBT effectively reduced depressive symptoms but showed limited impact on social functioning and healthcare costs. Personalised optimisation may modestly improve productivity and adjustment, suggesting its promise for enhancing social outcomes. Personalised tailoring of CBT skills may strengthen the effects of digital interventions on social functioning. UMIN000047124.

Abstract The existence of missing geomagnetic reversals has been proposed, with potential for new magnetostratigraphic age controls. We estimate geomagnetic reversal frequency from 0 to 155 Ma using adaptive‐bandwidth kernel density estimation (AKDE) to evaluate data sparseness and to assess how reversal frequency changes when recently identified geomagnetic reversals are incorporated into the geomagnetic polarity time scale (GPTS) data set. AKDE is a two‐stage procedure that uses an initial density estimator based on an initial (pilot) bandwidth. We found that the pilot bandwidth determined using cross‐validation is stable with respect to data set length. The AKDE results obtained based on the cross‐validated pilot bandwidth reveal four troughs after the Cretaceous Normal Superchron, spaced 13.5–15.0 Myr apart and corresponding to relatively long chrons (>0.8 Myr). One trough near 32 Ma becomes less distinct after the four recently identified reversals are added to the data set. This sensitivity suggests that troughs in the frequency curve may indicate missing geomagnetic reversals.

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are a novel therapeutic alternative to erythropoiesis-stimulating agents (ESAs) for anemia in chronic kidney disease. Evidence regarding their real-world effectiveness is still limited. We analyzed data from the Japanese Dialysis Outcomes and Practice Patterns Study (J-DOPPS, 2019–2022) to assess the real-world effectiveness of HIF-PHIs among maintenance hemodialysis patients. We compared patients who transitioned from ESAs to HIF-PHIs with those who continued ESAs, focusing on baseline characteristics and changes in anemia-related, iron metabolism, and inflammatory parameters. Among 1433 patients on ESAs, only 56 (3.9%) were switched to HIF-PHIs. Compared with the ESA continuation group, patients in the HIF-PHI group had poorer nutritional status (albumin: 3.3 vs. 3.6 g/dL; cholesterol: 142 vs. 156 mg/dL; respectively) and greater ESA resistance (erythropoietin resistance index: 18.4 vs. 8.5 IU/kg/week/g/dL, respectively), despite higher ESA doses and iron prescription rates. After switching, a significant increase in hemoglobin was observed at 1 month (+0.44 g/dL; 95% confidence interval: 0.05–0.82; p = 0.025). Serum iron and total iron-binding capacity levels also increased, while transferrin saturation and ferritin remained unchanged. A subgroup analysis suggested greater hemoglobin response in patients with high C-reactive protein levels (p for interaction = 0.074), but no difference by erythropoietin resistance index (p for interaction = 0.372). In routine clinical practice, HIF-PHIs were selectively prescribed to patients with treatment-refractory anemia. Treatment increased hemoglobin levels, with a suggestive trend toward greater effect among those with inflammation, supporting the potential utility of HIF-PHIs in complex anemia management.

Quantitative susceptibility mapping (QSM) on MRI quantifies tissue magnetic susceptibility, which increases with iron accumulation, myelin loss, and neuroinflammation. Elevated QSM in the substantia nigra (SN) has been reported in Lewy body disease and other parkinsonian disorders, but from existing literature it remains unclear whether these findings are driven by neurodegeneration-related iron deposition or other neuropathologic features. We studied 59 autopsied participants who underwent antemortem 3T MRI with QSM (median age at death, 78.5years; MRI-to-death interval, 2.0years), including clinical diagnoses of 18 with Alzheimer's-type dementia, 15 cognitively unimpaired, 9 with mild cognitive impairment, and 9 with dementia with Lewy bodies. A machine learning-incorporated digital histopathology pipeline quantified tau burden, iron deposition, and neuronal densities. The SN was divided into geometric quadrants, and QSM values were analyzed in relation to corresponding neuropathologic measures within each quadrant. Iron deposition correlated with QSM in all quadrants (ρ = 0.41-0.56, all P < 0.005). Tau burden correlated with QSM in the ventromedial (VM) quadrant (ρ = 0.45, P = 0.002), whereas lower pigmented neuron density was associated with higher QSM in the dorsomedial quadrant (ρ = -0.35, P = 0.007). Rank regression analysis confirmed iron as the strongest predictor of QSM across all quadrants (β = 0.35-1.06, P ≤ 0.026), with tau independently associated with QSM in the VM (β = 0.45, P = 0.015). Mediation analysis demonstrated that tau exerted direct (0.45, P = 0.018) and indirect effects via iron (0.12, P = 0.046) on QSM in the VM, with 80% of the effect being direct. These findings underscore the contributions of tau pathology, pigmented neuron density, and iron deposition to nigral magnetic susceptibility and highlight the potential for QSM to serve as a sensitive biomarker for diverse neuropathologies.

The concept of the ecological niche, defined as the basic habitat requirements for a species, is central to understanding species geographic distributions and predicting their responses to environmental change. However, identifying the essential niche for large regional communities remains a challenge because niche axes can be "hidden" by the complexity of the underlying ecological processes. Here, applying advanced species distribution modelling to nationwide environmental DNA survey data, we identified hidden niche axes of the Japanese coastal fish community and investigated the response diversity to these axes. Our survey detected 1,220 coastal fish species. The hidden niche axes collectively explained most of the variation in fish biodiversity and revealed five biogeographic boundaries for the regional community. These niches of the Japanese fish community may primarily relate to several processes due to ocean currents, such as environmental filters, transport from source areas and dispersal barriers. We also found that the response diversity to niche axes was positively correlated with species richness, although local communities with particularly high response diversity were geographically biased. A better understanding of the niche axes of the regional ecological community should help to mitigate the loss of biodiversity and ecosystem services caused by ongoing environmental change.

Abstract To test whether geophysical anomalies contribute to earthquake forecasts beyond the inherent clustering effects in seismicity, we develop a self and external excitation point‐process model by incorporating anomalies into the temporal Epidemic‐Type Aftershock Sequence (ETAS) model. The model is applied to earthquakes that occurred between 2001 and 2010 around the Kakioka (KAK) station in Japan, with two types of anomalies, ultralow frequency (ULF) magnetic anomalies and carbon monoxide (CO) anomalies, as external excitations. Results indicate that 14.33% of the earthquakes can be interpreted by the external excitation of anomalies. Proposed ETAS + ULF + CO model achieves an overall probability gain of 1,013.55 in forecasting 218 earthquakes compared to the purely temporal ETAS model. Statistical significance is assessed by fitting the same model to the same earthquake catalog but with randomized anomaly occurrence times, confirming that the performance improvement is not due to overfitting. These findings highlight the potential for enhancing short‐term earthquake forecasts using non‐seismic precursors, particularly when multiple precursors are combined.

We can directly sample from the conditional distribution of any log-affine model. The algorithm is a Markov chain on a bounded integer lattice, and its transition probability is the ratio of the UMVUE (uniformly minimum variance unbiased estimator) of the expected counts to the total number of counts. The computation of the UMVUE accounts for most of the computational cost, which makes the implementation challenging. Here, we investigated an approximate algorithm that replaces the UMVUE with the MLE (maximum likelihood estimator). Although it is generally not exact, it is efficient and easy to implement; no prior study is required, such as about the connection matrices of the holonomic ideal in the original algorithm.