Background: In April 2016, Japan mandated higher-level hospitals (ie, Special Functioning Hospitals [SFHs] and Regional Medical Care Support Hospitals [RMCSHs] with ≥500 beds) to charge additional fees for non-referral first visits to facilitate hospital function differentiation. The mandate expanded to RMCSHs with 400–499 beds and 200–399 beds in April 2018 and April 2020, respectively. We investigated changes in referral rates (proportion of referred to first-visit patients) before and after the fee’s implementation.

Methods: Using a community-based insurance claims database from a single prefecture in Japan, we extracted claims for first visits to hospitals with ≥200 beds between April 2014 and March 2022 and calculated monthly referral rates to five hospital groups (SFHs, RMCSHs with ≥500, 400–499, and 200–399 beds, and non-designated hospitals with ≥200 beds). We conducted a controlled interrupted time-series analysis by hospital category, treating non-designated hospitals as controls.

Results: Of 405,087 first-visit patients (mean age 54.9; standard deviation, 20.2 years; 53.2% female), 157,734 (38.9%) had a referral. The average referral rate to SFHs was high pre-mandate and did not increase. With the mandate, referral rates to RMSCHs with ≥500 beds and 400–499 beds rose by 5.10% points (95% confidence interval [CI], 1.84–8.35) in 2016 and 4.49% points (95% CI, 0.28–8.70) in 2018, respectively, and stabilized afterward. Referral rates to RMCSHs with 200–399 beds remained unchanged.

Conclusion: Average referral rates increased when the additional fee was mandated for RMCSHs with ≥400 beds, although the influence on health outcomes remains unclear.

Background: Meningococcal infection remains a life-threatening disease despite advances in early recognition and therapy. While the incidence of meningococcal infection is extremely low in Japan, nationwide data on its clinical outcomes have been lacking.

Methods: We conducted a retrospective cohort study using the Japanese Diagnosis Procedure Combination (DPC) inpatient database from July 2010 to March 2023. Patients with a main diagnosis of meningococcal infection (International Classification of Diseases, 10^th Revision code A39) were included. The primary outcome was in-hospital mortality. Secondary outcomes included impaired consciousness at discharge and functional status, assessed using the Barthel Index. Multivariable logistic regression was performed to identify prognostic factors.

Results: A total of 465 patients were analyzed. The median age was 55 years, and 57.0% were male. The in-hospital mortality rate was 8.2%, and 40.2% of survivors had a Barthel Index ≤90 at discharge. Early antibiotic administration did not significantly reduce mortality but was associated with improved neurological outcomes. Baseline impaired consciousness was the strongest predictor of mortality and poor functional status, while chronic comorbidities also contributed to worse outcomes. Notably, older age itself was not independently associated with mortality after adjustment for severity and comorbidities.

Conclusion: Meningococcal infection outcomes in Japan are predominantly determined by the severity of illness at presentation and comorbid health conditions rather than age alone. Early antibiotic therapy improves neurological recovery but may not prevent death once critical illness is established. These findings underscore the importance of prevention through vaccination and early recognition strategies to reduce the burden of this devastating infection.

Background: Policy decisions should be guided by measures that capture the impact of exposures on outcomes and that explicitly account for present-day exposure distribution. Both the preventable and attributable fractions have been used for this purpose; however, exposure effects can vary across subpopulations, and when this occurs, appropriate interpretation of these measures should be facilitated by a discussion of the contributions of different subpopulations.

Methods: We analyze preventable and attributable fractions in the presence of effect modification. In particular, we use potential outcomes to formally define these quantities and to clarify the weighting of different strata in the total population measures.

Results: Our derivations show that stratum-specific preventable and attributable fractions are weighted in proportion to the relative frequencies of effect modifiers among individuals with the outcome of interest. We also demonstrate that these weights are valid for the related quantities, preventable and attributable proportions. Finally, we present an example that illustrates how effect modification affects interpretation of these measures.

Conclusion: In sum, when effect modification is present, investigators should consider reporting these measures by the relevant population strata, and information that would allow quantification of their implicit weights in the total population estimate. Our study provides a formal justification for this approach.