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Abstract Background The proportions of preterm birth (PTB, ie., delivered before 37 gestational weeks) and low birth weight (LBW, ie., birth weight less than 2500 g at delivery) have been rising in developed countries. We sought to examine the factors contributing to the rise in Japan, with particular focus on the effects of obstetric interventions. Methods We used a database maintained by one large regional hospital in Shizuoka, Japan. We restricted the analysis to mothers who delivered live singleton births from 1997 to 2010 (n = 19,221). We assessed the temporal trends in PTB and LBW, then divided the study period into four intervals and compared the proportions of PTB and LBW. We also compared the newborns’ outcomes between the intervals. Results PTB, in particular medically indicated PTB, increased considerably. The increase was largely explained by changes in caesarean sections. The neonatal outcomes did not worsen, and instead the Apgar scores and proportions requiring neonatal intensive care unit (NICU) admission improved. In particular, the risks of NICU admission in the interval from 2007 to 2010 were decreased among all births [odds ratio (OR): 0.84; 95% confidence interval (CI): 0.75, 0.95] and medically indicated births (OR: 0.44; 95% CI: 0.29, 0.68) compared with the interval from 1997 to 2000. Conclusions Despite the increases in PTB as well as LBW, the present study suggests benefits of obstetric interventions. Rather than simple categorization of PTB or LBW, indicators such as perinatal mortality or other outcomes may be more appropriate for evaluation of perinatal health in developed countries.

Introduction: Gastroesophageal reflux disease (GERD) is characterized by esophageal mucosal injury due to the reflux of gastroduodenal contents. Typical symptoms include heartburn and acid regurgitation. In addition, gastroesophageal reflux (GER) can influence conditions such as otitis media, rhinitis, and asthma. This study aimed to examine the association between dinner-to-bed time and GER-related diseases, such as otitis media, allergic rhinitis, and asthma., Methods: This was a longitudinal cohort study using secondary data. Data were collected from a large-scale birth cohort study conducted in Japan including babies born in 2001 and 2010. Dinner-to-bed time was categorized as "longer dinner-to-bed time" (>120 minutes), "shorter dinner-to-bed time" (≤120 minutes or less), and "irregular dinner-to-bed time." Modified Poisson regression with robust variance was used to estimate risk ratios (RRs)., Results: A total of 60,392 children were included in this study. Children with shorter dinner-to-bed time had a higher risk of asthma (adjusted RR (aRR) = 1.10; 95% confidence interval (CI), 1.03-1.18) than those with longer dinner-to-bed time. However, no significant association was observed between shorter dinner-to-bed time and otitis media or allergic rhinitis. Furthermore, supplementary analyses revealed that the risk of asthma was significantly higher in children born in 2001 (aRR = 1.13; 95% CI, 1.04-1.22)., Conclusion: This study showed that dinner-to-bed time within 120 minutes after dinner increases the risk of developing asthma. This underscores the importance of considering lifestyle modifications, as certain pediatric asthma cases may be influenced by behaviors that promote GER., Competing Interests: Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. Ethics Committee of Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences and Okayama University Hospital issued approval 1506-073. This study was conducted in accordance with the 2013 Declaration of Helsinki. It involved secondary analysis of anonymized data from "The Longitudinal Survey of Babies in the 21st Century," with informed consent obtained from all original participants. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: Takashi Yorifuji declare(s) a grant from JSPS KAKENHI. 20K10498. Naomi Matsumoto declare(s) a grant from JSPS KAKENHI. 23K16329. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2025, Uraguchi et al.)

The long-term effects of cesarean delivery (CD) on child health and development remain controversial. This study aimed to investigate these effects using an outcome-wide approach in a Japanese context, where perinatal mortality rates are among the world's lowest. We analyzed data from 2,114 children in a nationwide Japanese birth cohort, linking the 21st Century Longitudinal Survey of Newborns with the Perinatal Research Network database. We examined associations between CD and various health and developmental outcomes up to 9 years of age, including hospitalizations, obesity, and developmental milestones. After adjusting for potential confounders, CD was not significantly associated with most outcomes, including all-cause hospitalization (adjusted risk ratio 1.25, 95% CI 0.997-1.56), obesity at 5.5 and 9 years, and various developmental milestones. Subgroup analyses for multiple births and preterm infants showed some differences in point estimates, but were limited by small sample sizes. CD was not significantly associated with adverse long-term child health or developmental outcomes in this Japanese cohort. These findings provide reassurance regarding CD safety when medically indicated in advanced perinatal care settings. Further research with larger samples and longer follow-up is needed, especially for specific subgroups., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Consent statement: This study used data from the Longitudinal Survey of Babies in the 21st Century conducted by the Ministry of Health, Labour and Welfare of Japan (MHLW) and the Perinatal Research Network database from the Japan Society of Obstetrics and Gynecology. As both datasets were fully anonymized for secondary use, informed consent was not required. The use of these data for this study was approved by the respective data holders. Declaration of generative AI and AI-assisted technologies in the writing process During the preparation of this work the authors used an AI-powered language model (Claude) in order to assist with English language editing and proofreading. After using this tool/service, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication., (© 2025. The Author(s).)

Background: The incidence of allergic diseases has been increasing in Japan. In particular, a serious decline in the age of onset of allergic rhinitis has been observed. Passive smoking from parental smoking has a significant impact on children's health; however, it is difficult to restrict smoking in the home. While various studies have previously reported on the relationship between passive smoking and the development of allergic diseases in children. However, there have been no reports on passive smoking and allergic diseases on a national scale., Methods: Using Japanese national longitudinal survey data (n = 38,444) for newborns born between May 10 and 24, 2010, we assessed parental smoking habits when their children were 6 months old and investigated the association with the development of allergic diseases until the age of 5.5 years. The risk ratios and 95% confidence intervals for the development of different allergic diseases were analyzed after adjusting for potential confounders using Poisson regression with a robust error variance., Results: The risk ratio for developing allergic rhinitis/allergic conjunctivitis (AR/AC) in children was significantly higher in the maternal smoking groups ( ≦ 10 cigarettes/day; RR 1.15, 95% CI 1.02-1.30; ≧11 cigarettes/day; RR 1.16, 95% CI 0.93-1.44). Furthermore, associations were found between the maternal smoking group in the presence of paternal smoking and the risk of developing bronchial asthma ( ≦ 10, RR 1.33 95% CI 1.17-1.52; ≧11, RR 1.71 95% CI 1.38-2.1), food allergy ( ≦ 10, RR 1.36 95% CI 1.12-1.63; ≧11, RR 1.25 95% CI 0.84-1.86), atopic dermatitis ( ≦ 10, RR 1.42 95% CI 1.22-1.66; ≧11, RR 1.6 95% CI 1.2-2.13), and AR/AC ( ≦ 10, RR 1.21 95% CI 1.07-1.36; ≧11, RR 1.35 95% CI 1.09-1.67)., Conclusions: Maternal smoking during infancy increases the risk of developing AR/AC in children. Considering paternal smoking, maternal smoking further increased the risk of developing allergic diseases in children, suggesting that reducing parental smoking at home may reduce the risk of developing allergic diseases in children., Competing Interests: Declarations. Ethics approval and consent to participate: This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Institutional Review Board of the Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences (No. 1506-073). Consent for publication: This manuscript does not contain any individual person’s data. Informed consent is not necessary for this paper. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

We herein present the case of a 21-year-old male Japanese diabetic patient with Temple syndrome, caused by maternal uniparental disomy of chromosome 14. The patient was overweight and had type 2 diabetes, dyslipidemia, metabolic dysfunction-associated steatotic liver disease, and microalbuminuria. He had an increased fat mass in the truncal region and a decreased lean mass throughout the body. This may lead to insulin resistance due to the absence of delta-like homolog 1 (DLK1) and retrotransposon gag-like 1 (RTL1). The patient had experienced social withdrawal at home (hikikomori in Japanese), had poorly controlled type 2 diabetes, and was overweight despite receiving diet therapy and oral hypoglycemic agents.

Evidence about which types of mask are effective in preventing infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is limited. We examined which mask types were effective against SARS-CoV-2 infection in a cluster setting in Japan. We retrospectively reviewed data from a cluster of COVID-19 cases that occurred at a manufacturing company in mid-August 2021. We included a total of 87 individuals who reported the type of mask worn. We dichotomized the types of mask into non-woven masks or other types of mask, such as cloth or urethane masks. We then examined the associations between the mask type and SARS-CoV-2 infection using logistic regression analysis, adjusting for potential confounders. Participants who wore non-woven masks were less likely to be infected with SARS-CoV-2 (9.7%) compared with those who wore other types of mask (26.7%). After adjusting for potential confounders, wearing a non-woven mask was significantly associated with a reduced risk of infection compared with wearing other mask types (odds ratio = 0.10, 95% confidence interval: 0.01 to 0.80). Non-woven masks were found to be more effective in preventing SARS-CoV-2 infection in a cluster setting than other types of mask, such as cloth or urethane masks.

Injury recurrence in young children is a significant public health concern, as it may indicate an unfavorable home environment. This study evaluates whether infantile injuries increase recurrence during preschool years, contributing to more effective prevention strategies for vulnerable families. The study included 20,191 children from "The Longitudinal Survey of Babies in the 21st Century," a representative sample of infants born in Japan between May 10 and 24, 2010. We conducted a logistic regression analysis to compare injury recurrence risk between children aged 18 months to seven years with and without infantile injury histories. The study revealed that infants with a history of injuries had a higher risk of subsequent hospital visits for injuries during preschool years (crude Odds Ratio (cOR) 1.52, 95% CI, 1.41-1.64, adjusted OR (aOR) 1.48, 95% CI 1.37-1.60). Specific injuries, such as falls (aOR 1.34, 95% CI, 1.26-1.43), pinches (aOR 1.22, 95% CI, 1.15-1.29), drowning (aOR 1.29, 95% CI, 1.19-1.40), ingestion (aOR 1.35, 95% CI, 1.17-1.55), and burns (aOR 1.47, 95% CI, 1.31-1.65), independently increased the risk of future injuries. Our findings highlight the necessity of universal safety measures in the home environment and targeted interventions for families with a history of high-risk injuries., (© 2024. The Author(s).)

Kawasaki disease (KD) is a pediatric disease of unknown etiology that commonly affects infants in East Asia. Infants born small for gestational age (SGA) have weaker immune systems and are more susceptible to infection. Using data from a nationwide Japanese birth cohort study conducted in 2010 (n=34,579), we investigated whether SGA increases the risk of KD. SGA was defined as birth weight below the 10th percentile for gestational age. The outcome was hospitalization for KD between 6 and 30 months of age. The association between SGA and hospitalization for KD, adjusted for child and maternal factors, was examined using logistic regression. Of the 231 children hospitalized for KD, 9.5% were SGA. Further statistical analysis showed that SGA did not increase the odds ratio (OR) of hospitalization for KD (adjusted OR 1.12, 95% confidence interval 0.71-1.75). This result was not changed with stratification by early daycare attendance and preterm status. Reasons for the lack of association may include the multifactorial pathogenesis of KD; in addition, the types of infections to which SGA infants are predisposed may differ from those triggering KD. Overall, our large nationwide study found no association between SGA and KD., Competing Interests: No potential conflict of interest relevant to this article was reported.

Background: Previous research has suggested a correlation between postnatal maximum weight loss (MWL) and both neonatal mortality and morbidities in extremely preterm infants. However, the relationship between MWL and neurodevelopmental outcomes remains underexplored., Methods: In a single-center, retrospective cohort study at Okayama Medical Center, we evaluated data from extremely preterm infants admitted to the neonatal intensive care unit from 2010 to 2020. Infants who died within the first 10 days of life were excluded. MWL in the first 10 days was the main exposure, categorized into three groups: >15%, 5-15%, and < 5%. The primary outcome evaluated was the occurrence of death or neurodevelopmental impairment (NDI) at age 3 years, defined as developmental impairments (developmental quotient [DQ] < 85), cerebral palsy, hearing impairments, or visual impairments. Data analysis involved robust Poisson regression, adjusted for perinatal confounders, with a restricted cubic spline function to examine the dose-response relationship. We also conducted a sensitivity analysis using a DQ of < 70 to define developmental impairment., Results: Among 135 infants assessed for neurodevelopmental outcomes, 40 were in the > 15% MWL group, 71 in the 5-15% group, and 24 in the < 5% group. Median gestational ages and birth weights were 25.9 weeks and 821 g for > 15% MWL; 26.1 weeks and 818 g for 5-15% MWL; and 26.0 weeks and 734 g for < 5% MWL. Compared with the 5-15% MWL group, the < 5% group exhibited a higher risk of death or NDI at age 3 years (62.8% vs. 80.8%, risk ratio [RR] 1.36, 95% confidence interval [CI] 1.04-1.79) and NDI alone (59.2% vs. 79.2%, RR 1.43, 95% CI 1.06-1.94). Furthermore, higher risks of developmental impairment were also noted in the > 15% (RR 1.32, 95% CI 1.00-1.75) and < 5% (RR 1.46, 95% CI 1.08-1.98) groups. These associations were confirmed by spline analyses. In contrast, the associations between MWL and neurodevelopmental outcomes using a DQ of < 70 were not apparent., Conclusions: MWL within the first 10 days of life may be associated with increased risks of NDI and developmental impairments by age 3 years in extremely preterm infants., (© 2024. The Author(s).)

This study aimed to examine the efficacy and safety of protein and/or essential amino acid (EAA) supplementation in all lower limb surgeries using systematic reviews and meta-analysis of randomized controlled trials (RCTs). We included RCTs that assessed the efficacy of protein and/or EAA supplementation in lower limb surgeries. On June 2, 2023, we searched EMBASE, MEDLINE, the Cochrane Central Register of Controlled Trials, the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. The primary outcomes were mobility, patient-reported outcomes (PRO), and acute kidney injury (AKI). The secondary outcomes were exercise capacity, muscle strength, muscle mass, and all adverse events. We performed meta-analyses using the random-effects model. We assessed the risk of bias using the Cochrane risk-of-bias tool and the certainty of evidence using the Grading of Recommendations, Assessment, Development, and Evaluation approach. We included 12 RCTs (622 patients). These studies included four on hip fracture surgery, three on total hip arthroplasty, and five on total knee arthroplasty. Protein and/or EAA supplementation may slightly improve PRO (standard mean difference 0.51, 95% confidence interval (CI): 0.22 to 0.80, low certainty of evidence). Nevertheless, it may not improve mobility (mean difference 0.07 m/s, 95% CI: -0.01 to 0.16, low certainty of evidence). No adverse events including AKI were reported. Muscle strength may have increased (standard mean difference 0.31, 95% CI: 0.02 to 0.61, very low certainty of evidence). However, exercise capacity (mean difference 5.43 m, 95% CI: -35.59 to 46.45, very low certainty of evidence) and muscle mass (standard mean difference -0.08, 95% CI: -0.49 to 0.33, very low certainty of evidence) were not improved. While protein and/or EAA supplementation in lower limb surgeries may improve PRO, it is unlikely to affect mobility. Despite this, the medical team and patients might still consider protein and/or EAA supplementation a useful option., Competing Interests: Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Hagiyama et al.)

Competing Interests: None

Background: Many outbreaks of coronavirus disease 2019 have occurred in Japanese nursing homes in which residents and staff are in close daily contact. This study evaluated longitudinal changes in antibody titers in nursing homes in which clusters occurred and examined the association between antibody titer and the severe acute respiratory syndrome coronavirus 2 infection or severity., Methods: This cohort study included 171 participants who had provided at least one antibody titer test between June 2022 and March 2023. A descriptive analysis estimated the association between the risk of infection and antibody titer level., Results: The facility experienced 2 clusters during the study period that involved facility staff as the initial source of infection. Noninfected participants had less variation in antibody titer levels and a higher level of preinfection antibodies than infected participants. The risk of infection and severity was lower in participants with higher antibody titers than in those with lower titers., Conclusions: We showed the changes in antibody titers over time and the association between antibody titer and severe acute respiratory syndrome coronavirus 2 infection or severity. Vaccination schedules may need to be tailored to the dynamics of decreasing antibody titers over time and the occurrence of infectious diseases in facilities., (Copyright © 2024 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.)

Background: While positive pressure ventilation has been considered an important contributing factor associated with pulmonary air leaks, studies examining the association between specific ventilatory settings during acute-phase high-frequency oscillatory ventilation (HFOV) and pulmonary air leaks among extremely preterm infants are limited., Methods: This was a single-center retrospective cohort study conducted at an institution that primarily used HFOV after intubation in extremely preterm infants. We analyzed data from extremely preterm infants born between 2010 and 2021. The primary outcome was pulmonary air leakage during the first 7 days of life. The exposure variable was the maximum mean airway pressure (MAP) on HFOV during the first 7 days of life or before the onset of pulmonary air leaks. Maximum MAP was categorized into three groups: low (7-10 cmH 2 O), moderate (11-12 cmH 2 O), and high (13-15 cmH 2 O) MAP categories. We conducted robust Poisson regression analyses after adjustment for perinatal confounders, using the low MAP category as the reference., Results: The cohort included 171 infants (low MAP, 123; moderate MAP, 27; and high MAP, 21). The median (interquartile range) gestational age and birth weight were 25.7 (24.3-26.7), 25.7 (24.9-26.9), and 25.3 (24.3-26.6) weeks and 760 (612-878), 756 (648-962), and 734 (578-922) g for infants in the low, moderate, and high MAP categories, respectively. Compared to infants in the low MAP category, those in the high MAP category had a higher incidence of pulmonary air leaks (4.1% vs. 33.3%; adjusted risk ratio, 5.4; 95% confidence interval, 1.6-18.5). In contrast, there was no clear difference in the risk of pulmonary air leaks between the moderate and low MAP categories (3.7% vs. 4.1%; adjusted risk ratio, 0.9; 95% confidence interval, 0.1-6.1)., Conclusion: Extremely preterm infants requiring high MAP (≥13 cmH 2 O) in acute-phase HFOV had a higher risk of pulmonary air leak during the first 7 days of life., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Tamai, Takeuchi, Nakamura, Nakamura, Matsumoto, Yorifuji and Kageyama.)

Background: The impact of the sex of bystanders who initiate cardiopulmonary resuscitation (CPR) on out-of-hospital cardiac arrest (OHCA) patients has not been fully elucidated. This study aims to investigate the association between the sex of bystanders who perform CPR and the clinical outcomes of OHCA patients in real-world clinical settings., Methods: We conducted a retrospective, observational study using data from the Okayama City Fire Department in Japan. Patients were categorized based on bystanders' sex. Our primary outcomes were return of spontaneous circulation (ROSC). Our secondary outcome was 30-day survival and 30-day favorable neurological outcome, defined as Cerebral Performance Category score of 1 or 2. Multivariable logistic regression analysis was used to examine the association between these groups and outcomes., Results: The study included 3,209 patients with a comparable distribution of male (1,540 patients: 48.0%) and female bystanders (1,669 patients: 52.0%) between the groups. Overall, 221 (6.9%) ROSC at hospital arrival, 226 (7.0%) patients had 30-day survival, and 121 (3.8%) patients had 30-day favorable neurological outcomes. Bystander sex (female as reference) did not contribute to ROSC at hospital arrival (adjusted OR [aOR] 1.11, 95% CI: 0.76-1.61), 30-day survival (aOR 1.23, 95% CI: 0.83-1.82), or 30-day favorable neurological outcomes (aOR 0.66, 95% CI: 0.34-1.27). Basic life support education experience was a bystander factor positively associated with ROSC. Patient factors positively associated with ROSC were initial shockable rhythm and witness of cardiac arrest., Conclusion: There were no differences in ROSC, 30-day survival, or 30-day neurological outcomes in OHCA patients based on bystander sex., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)