Background: Pre-pregnancy underweight (BMI <18.5 kg/m²) is notably prevalent among reproductive-aged Japanese women, affecting approximately 20%, compared to less than 10% in Western countries. However, its overall impact on maternal and infant outcomes in Japanese populations has not been systematically evaluated.

Methods: We conducted a systematic review and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. MEDLINE, EMBASE, CINAHL, PsycINFO, Cochrane Library, and Ichushi were searched from inception to February 2024. Cohort and case-control studies examining associations between pre-pregnancy underweight and perinatal outcomes in Japanese women with singleton pregnancies were included. Primary outcomes were low birth weight (LBW), small for gestational age (SGA), and preterm birth (PTB). Random-effects models calculated pooled odds ratios (ORs) with 95% confidence intervals (CIs).

Results: Thirty-four studies were analyzed. Pre-pregnancy underweight significantly increased risks of LBW (OR 1.61; 95% CI, 1.38–1.86), SGA (OR 1.59; 95% CI, 1.55–1.63), and PTB (OR 1.23; 95% CI, 1.19–1.26). Mean birth weight was 115.02 g lower (95% CI, −128.05 to −101.99) in underweight mothers.

Conclusion: Pre-pregnancy underweight among Japanese women is significantly associated with increased risks of adverse perinatal outcomes. Notably, these elevated risks persist despite the high background prevalence of underweight, suggesting that their adverse effects are not diminished in populations where it is more common. These findings underscore the importance of increasing awareness of preconception care and emphasize the need to optimize pre-pregnancy weight.

Background: Herpes simplex virus encephalitis (HSE) is a rare but life-threatening condition. While the disease has been well characterized in Western countries, large-scale epidemiological data from Japan are lacking.

Methods: Using the Ministry of Health, Labour and Welfare (MHLW) Diagnosis Procedure Combination (DPC) Study Group database, we identified patients hospitalized with HSE between July 2010 and March 2023. Patients were identified using International Classification of Diseases, 10^th Revision codes. Nationwide incidence was estimated by multiplying the observed case counts by the annual ratio of total discharges in the national MHLW-DPC database to those in the DPC Study Group. We used generalized estimating equations to account for clustering within hospitals in multivariable models. In-hospital mortality and functional and neurological outcomes were assessed. Multivariable logistic regression identified prognostic factors.

Results: A total of 6,788 patients were identified. The annual incidence of HSE ranged from 5.7 to 8.2 per 100,000 hospitalizations. Overall, in-hospital mortality was 6.0%. Of 6,378 survivors, 2,295 (36.0%) had a Barthel Index score ≤90 and 1,602 (25.1%) had impaired consciousness (Japan Coma Scale ≥1) at discharge. A composite poor outcome (death or impaired consciousness) occurred in 2,012 (29.6%). Older age (especially ≥80 years), impaired consciousness at presentation, and comorbidities such as congestive heart failure, chronic renal disease, malignancy, and underweight status were associated with in-hospital mortality and poor outcomes.

Conclusion: This multicenter analysis of HSE in Japan showed that HSE was associated with substantial disability among survivors, in addition to non-negligible mortality. Our findings highlight the need for post-acute rehabilitation to reduce the burden of residual disability.

Background: The Shanghai University of Sport (SUS) Longitudinal Cohort Study (SUS Cohort) was established to investigate the influence of lifestyle and modifiable behavioral factors in early adulthood on the development of non-communicable diseases (NCDs) later in life. The cohort aims to identify novel biomarkers and explore mechanisms underlying chronic diseases using a multi-omics approach.

Methods: The SUS Cohort study is a prospective cohort study of undergraduate students between 2018 and 2019, with follow-ups conducted every 2 years during early adulthood and every 10 years thereafter. Comprehensive data collection includes body composition measurements, lifestyle surveys, physical fitness tests, and clinical laboratory tests. Multi-omics analysis, including genome-wide genotyping, gut microbiome, and serum metabolome, is integrated to provide insights into disease pathophysiology.

Results: A total of 1,758 participants aged 18 to 22 (mean age 18.64; standard deviation, 3.15) years were conducted from baseline surveys, with a follow-up period between September 2021 and September 2022. The median age at baseline was 18 years, and female participants accounted for 49.5% of the cohort (n = 870). Of the initial participants, 1,055 individuals (60%) completed the follow-up.

Conclusion: The SUS Cohort provides multidimensional data to study how early-life factors influence long-term health outcomes.