DPC, which is an acronym for “Diagnosis Procedure Combination,” is a patient classification method developed in Japan for inpatients in the acute phase of illness. It was developed as a measuring tool intended to make acute inpatient care transparent, aiming at standardization of Japanese medical care, as well as evaluation and improvement of its quality. Subsequently, this classification method came to be used in the Japanese medical service reimbursement system for acute inpatient care and appropriate allocation of medical resources. Furthermore, it has recently contributed to the development and maintenance of an appropriate medical care provision system at a regional level, which is accomplished based on DPC data used for patient classification. In this paper, we first provide an overview of DPC. Next, we will look back at over 15 years of DPC history; in particular, we will explore how DPC has been refined to become an appropriate medical service reimbursement system. Finally, we will introduce an outline of DPC-related research, starting with research using DPC data.

Background: While duodenal ulcer (DU) and gastric cancer (GC) are both H. pylori infection-related diseases, individuals with DU are known to have lower risk for GC. Many epidemiological studies have identified the PSCA rs2294008 T-allele as a risk factor of GC, while others have found an association between the rs2294008 C-allele and risk of DU and gastric ulcer (GU). Following these initial reports, however, few studies have since validated these associations. Here, we aimed to validate the association between variations in PSCA and the risk of DU/GU and evaluate its interaction with environmental factors in a Japanese population.

Methods: Six PSCA SNPs were genotyped in 584 DU cases, 925 GU cases, and 8,105 controls from the Japan Multi-Institutional Collaborative Cohort (J-MICC). Unconditional logistic regression models were applied to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between the SNPs and risk of DU/GU.

Results: PSCA rs2294008 C-allele was associated with per allele OR of 1.34 (95% CI, 1.18–1.51; P = 2.28 × 10⁻⁶) for the risk of DU. This association was independent of age, sex, study site, smoking habit, drinking habit, and H. pylori status. On the other hand, we did not observe an association between the risk of GU and PSCA SNPs.

Conclusions: Our study confirms an association between the PSCA rs2294008 C-allele and the risk of DU in a Japanese population.

Background: Although the consumption of vegetables and fruits is reported to influence the risk of cataract, no prospective study of this association from Asia has yet appeared. Here, we investigated the association between vegetable and fruit intake and cataract incidence in a large-scale population-based prospective cohort study in Japan.

Methods: This study included 32,387 men and 39,333 women aged 45–74 years who had no past history of cataract and had completed a dietary questionnaire of the Japan Public Health Center-based Prospective Cohort Study. The incidence of cataract was evaluated after 5-year follow-up. We used multiple logistic regression analyses to estimate the sex-specific odds ratios (ORs), with adjustment for confounding factors.

Results: We identified 1,836 incident cataracts in 594 men and 1,242 women. In men, the OR for cataract was decreased with higher intake of vegetables (OR_{Q5 vs Q1}, 0.77; 95% confidence interval [CI], 0.59–1.01; P_trend across quartile categories = 0.03) and cruciferous vegetables (OR_{Q5 vs Q1}, 0.74; 95% CI, 0.57–0.96; P_trend = 0.02). In contrast, the OR for cataract was increased with higher intake of vegetables among women (OR_{Q5 vs Q1}, 1.28; 95% CI, 1.06–1.53; P_trend = 0.01). Green and yellow vegetable and fruit intake were not associated with cataract in either sex.

Conclusions: This study suggests that vegetables may reduce the risk of cataract in men, but not in women.

Background: Alcohol consumption is a potential risk factor for gastric cancer. However, findings from cohort studies that examined the relationship between alcohol consumption and gastric cancer risk among Japanese population are not conclusive.

Methods: A total of 54,682 Japanese men and women participating in the Japan Collaborative Cohort study completed a questionnaire, including alcohol consumption information. The Cox proportional hazard model was used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs).

Results: After a median 13.4-year follow-up, we documented 801 men and 466 women incident cases of gastric cancer. Alcohol consumption was associated with increased risk of gastric cancer among men (HRs in ex-drinkers and current alcohol consumption of <23 g, 23–<46 g, 46–<69 g, and ≥69 g/d categories versus never drinkers were 1.82; 95% CI, 1.38–2.42, 1.41; 95% CI, 1.10–1.80, 1.47; 95% CI, 1.17–1.85, 1.88; 95% CI, 1.48–2.38, and 1.85; 95% CI, 1.35–2.53, respectively, and that for 10 g increment of alcohol consumption after excluding ex-drinkers was 1.07; 95% CI, 1.04–1.10). The association in men was observed for cardia and non-cardia gastric cancer (HRs in the highest alcohol consumption category versus never drinkers were 9.96; 95% CI, 2.22–44.67 for cardia cancer and 2.40; 95% CI, 1.64–3.52 for non-cardia cancer). However, no such trend was observed in women.

Conclusions: Alcohol consumption is associated with increased risk of gastric cancer among Japanese men, regardless of anatomical subsite of the cancer.

Background: Few studies have examined the association between seaweed intake and blood pressure in children. We conducted an intervention study to investigate whether seaweed intake affects blood pressure.

Methods: Subjects were children aged 4 to 5 years attending a preschool in Aichi Prefecture, Japan, in 2010. Among 99 students, 89 (89.9%) were enrolled in our study. Nori (dried laver), an edible seaweed widely consumed in Japan, was used as a dietary intervention. Children in the intervention group were asked to consume 1.76 grams per day of roasted nori in addition to standard meals for 10 weeks. Children in the control group consumed their usual diet. Before the intervention and at the 10th week of the intervention, children’s blood pressure was measured three times successively using an automated sphygmomanometer with subjects in a sitting position. Changes in systolic (SBP) and diastolic blood pressure (DBP) were compared between 55 children in the intervention group and 26 in the control group after adjustment for SBP and DBP before the intervention.

Results: Changes in SBP were −8.29 mm Hg in the intervention group and +0.50 mm Hg in the control group (P for difference in change = 0.051). Changes in DBP were −6.77 mm Hg in the intervention group and −0.05 mm Hg in the control group (P = 0.031). In girls, no difference in blood pressure changes was found between the intervention and control groups.

Conclusion: Nori intake lowered DBP level in boys. Seaweed intake might have preventive effects on elevated blood pressure in childhood.

Background: Recent research suggests that Japanese inter-prefecture inequality in the risk of death before reaching 5 years old has increased since the 2000s. Despite this, there have been no studies examining recent trends in inequality in the infant mortality rate (IMR) with associated socioeconomic characteristics. This study specifically focused on household occupation, environment, and support systems for perinatal parents.

Methods: Using national vital statistics by household occupation aggregated in 47 prefectures from 1999 through 2017, we conducted multilevel negative binomial regression analysis to evaluate occupation/IMR associations and joinpoint analysis to observe temporal trends. We also created thematic maps to depict the geographical distribution of the IMR.

Results: Compared to the most privileged occupations (ie, type II regular workers; including employees in companies with over 100 employees), IMR ratios were 1.26 for type I regular workers (including employees in companies with less than 100 employees), 1.41 for the self-employed, 1.96 for those engaged in farming, and 6.48 for unemployed workers. The IMR ratio among farming households was 1.75 in the prefectures with the highest population density (vs the lowest) and 1.41 in prefectures with the highest number of farming households per 100 households (vs the lowest). Joinpoint regression showed a yearly monotonic increase in the differences and ratios of IMRs among farming households compared to type II regular worker households. For unemployed workers, differences in IMRs increased sharply from 2009 while ratios increased from 2012.

Conclusions: Inter-occupational IMR inequality increased from 1999 through 2017 in Japan. Further studies using individual-level data are warranted to better understand the mechanisms that contributed to this increase.

Background: The impact of hospital surgical volume on long-term mortality has not been well assessed in Japan, especially for esophageal, biliary tract, and pancreatic cancer, although these three cancers need a high level of medical-technical skill. The purpose of this study was to examine associations between hospital surgical volume and 3-year mortality for these severe-prognosis cancer patients.

Methods: Patients who received curative surgery for esophageal, biliary tract, and pancreatic cancers were analyzed using the Osaka Cancer Registry data from 2006–2013. Hospital surgical volume was categorized into tertiles (high/middle/low) according to the average annual number of curative surgeries per hospital for each cancer. Three-year survivals were calculated using the Kaplan-Meier method. Hazard ratios (HRs) of 3-year mortality were calculated using Cox proportional hazard models, adjusting for patient characteristics.

Results: Three-year survival was higher with increased hospital surgical volume for all three cancers, but the relative importance of volume varied across sites. After adjustment for all confounding factors, HRs in middle- and low-volume hospitals were 1.34 (95% confidence interval [CI], 1.14–1.58) and 1.57 (95% CI, 1.33–1.86) for esophageal cancer; 1.39 (95% CI, 1.15–1.67) and 1.57 (95% CI, 1.30–1.89) for biliary tract cancer; 1.38 (95% CI, 1.16–1.63) and 1.90 (95% CI, 1.60–2.25) for pancreatic cancer, respectively. In particular for localized pancreatic cancer, the impact of hospital surgical volume on 3-year mortality was strong (HR 2.66; 95% CI, 1.61–4.38).

Conclusion: We suggest that patients who require curative surgery for esophageal, biliary tract, and pancreatic cancer may benefit from referral to high-volume hospitals.

Background: Previous studies have suggested the potential association between renal diseases and gallstone. The extent of proteinuria is recognized as a marker for the severity of chronic kidney disease. However, little data is available to identify the risk of incident gallstone according to the level of proteinuria.

Methods: Using a data of 207,356 Koreans registered in National Health Insurance Database, we evaluated the risk of gallstone according to the levels of urine dipstick proteinuria through an average follow-up of 4.36 years. Study subjects were divided into 3 groups by urine dipstick proteinuria (negative: 0, mild: 1+ and heavy: 2+ or greater). Multivariate Cox-proportional hazard model was used to assess the adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for incident cholelithiasis according to urine dipstick proteinuria.

Results: The group with higher urine dipstick proteinuria had worse metabolic, renal, and hepatic profiles than those without proteinuria, which were similarly observed in the group with incident cholelithiasis. The heavy proteinuria group had the greatest incidence of cholelithiasis (2.39%), followed by mild (1.54%) and negative proteinuria groups (1.39%). Analysis for multivariate Cox-proportional hazard model indicated that the heavy proteinuria group had higher risk of cholelithiasis than other groups (negative: reference, mild proteinuria: HR 0.97 [95% CI, 0.74–1.26], and heavy proteinuria: HR 1.46 [95% CI, 1.09–1.96]).

Conclusion: Urine dipstick proteinuria of 2+ or greater was significantly associated with increased risk for incident gallstone.

Background: We established a community-based cohort study to assess the long-term impact of the Great East Japan Earthquake on disaster victims and gene-environment interactions on the incidence of major diseases, such as cancer and cardiovascular diseases.

Methods: We asked participants to join our cohort in the health check-up settings and assessment center based settings. Inclusion criteria were aged 20 years or over and living in Miyagi or Iwate Prefecture. We obtained information on lifestyle, effect of disaster, blood, and urine information (Type 1 survey), and some detailed measurements (Type 2 survey), such as carotid echography and calcaneal ultrasound bone mineral density. All participants agreed to measure genome information and to distribute their information widely.

Results: As a result, 87,865 gave their informed consent to join our study. Participation rate at health check-up site was about 70%. The participants in the Type 1 survey were more likely to have psychological distress than those in the Type 2 survey, and women were more likely to have psychological distress than men. Additionally, coastal residents were more likely to have higher degrees of psychological distress than inland residents, regardless of sex.

Conclusion: This cohort comprised a large sample size and it contains information on the natural disaster, genome information, and metabolome information. This cohort also had several detailed measurements. Using this cohort enabled us to clarify the long-term effect of the disaster and also to establish personalized prevention based on genome, metabolome, and other omics information.

Background: The Adachi Child Health Impact of Living Difficulty (A-CHILD) study has been conducted since 2015 to clarify the associations between socioeconomic factors and child health, as well as to accumulate data for political evaluation of the child-poverty agenda. This paper describes the purpose and research design of the A-CHILD study and the baseline profiles of participants, together with the future framework for implementing this cohort study.

Methods: We have conducted two types of continuous survey: a complete-sample survey started in 2015 as a first wave study to target first-grade children in all public elementary schools in Adachi City, Tokyo, and a biennial fixed grade observation survey started in 2016 in selected elementary and junior high schools. Questionnaires were answered by caregivers of all targeted children and also by the children themselves for those in the fourth grade and higher. The data of A-CHILD also combined information obtained from school health checkups of all school-grade children, as well as the results from blood test and measurement of blood pressure of eight-grade children since 2016.

Results: The valid responses in the first wave were 4,291 (80.1%). The number of households in “living difficulties”, such as low household income or material deprivation, stood at 1,047 (24.5%).

Conclusions: The A-CHILD study will contribute to the clarification of the impact of poverty on children’s health disparities and paves the way to managing this issue in the community.