The effect of body mass index (BMI) on esophageal and gastric carcinogenesis might be heterogeneous, depending on subtype or subsite. However, findings from prospective evaluations of BMI associated with these cancers among Asian populations have been inconsistent and limited, especially for esophageal adenocarcinoma and gastric cardia cancer. We performed a pooled analysis of 10 population‐based cohort studies to examine this association in 394,247 Japanese individuals. We used Cox proportional hazards regression to estimate study‐specific hazard ratios (HRs) and 95% confidence intervals (CIs), then pooled these estimates to calculate summary HRs with a random effects model. During 5,750,107 person‐years of follow‐up, 1569 esophageal cancer (1038 squamous cell carcinoma and 86 adenocarcinoma) and 11,095 gastric (728 cardia and 5620 noncardia) cancer incident cases were identified. An inverse association was observed between BMI and esophageal squamous cell carcinoma (HR per 5‐kg/m² increase 0.57, 95% CI 0.50–0.65), whereas a positive association was seen in gastric cardia cancer (HR 1.15, 95% CI 1.00–1.32). A nonsignificant and significant positive association for overweight or obese (BMI ≥25 kg/m²) relative to BMI <25 kg/m² was observed with esophageal adenocarcinoma (HR 1.32, 95% CI 0.80–2.17) and gastric cardia cancer (HR 1.24, 95% CI 1.05–1.46), respectively. No clear association with BMI was found for gastric noncardia cancer. This prospective study—the largest in an Asian country—provides a comprehensive quantitative estimate of the association of BMI with upper gastrointestinal cancer and confirms the subtype‐ or subsite‐specific carcinogenic impact of BMI in a Japanese population.

The epidemiological and clinical characteristics, treatments, and outcomes of patients with coronavirus disease 2019 (COVID-19) who are admitted to the intensive care unit (ICU) have not been adequately evaluated in Japan. We analyzed the registry data of 205 patients with COVID-19 admitted to the ICU between February and November 2020, in Osaka Prefecture, Japan. A Cox proportional hazards model was used to assess the association between epidemiological factors and mortality among ICU patients. Of the 205 ICU patients, 161 (78.5%) were men and 149 (72.7%) were older than 60 years. A total of 117 patients (57.1%) had comorbidities. The most common symptoms at diagnosis were mild (n = 131, 63.9%). A total of 187 patients (91.2%) received mechanical ventilation, and 32 patients (15.6%) required extracorporeal membrane oxygenation. Patients were followed up for a median of 25 days after ICU admission. A total of 147 patients (71.7%) were alive at discharge, and 58 patients (28.3%) died. The hazard ratio for mortality among patients aged >80 years was 6.02 (95% confidence interval: 2.10−17.25) in the multivariable model, which was higher than that among those aged ≤59 years. These results are useful for recognizing the clinical course of this infection in ICU patients.

Aim To evaluate mortality among Japanese Olympic athletes compared with the general population and also evaluate their mortality based on total number of Olympics participation and intensity of sports disciplines. Methods Information on biography, vital status, date of birth, date of death and latest follow-up date on Japanese Olympians was retrieved from six online databases and compared. Standardised mortality ratio (SMR) was estimated according to observation periods and years from last participation in the Olympics. To further evaluate the association between mortality and total number of Olympics participation/intensity of sports disciplines within the study population, rate ratios (RRs) adjusted by sex, observation period and attained age group were estimated by a Poisson regression model. Results A total of 3381 Olympians were included in the analysis. The total person years was 94 076.82. The deaths of 153 (4.53%) Olympians were confirmed, and the overall SMR was 0.29 (95% CI, 0.25 to 0.34). SMRs categorised by years from last participation did not differ significantly. Higher mortality was observed among those who participated in the Olympics twice (RR: 1.52; 95% CI, 1.04 to 2.23) and three times or more (RR: 1.87; 95% CI, 1.08 to 3.25) compared with those who participated just once. Compared with combination of low static and low dynamic intensity category, higher mortality was observed in most combinations of middle-intensity or high-intensity categories. Conclusion Japanese Olympians lived longer than the general population. More frequent participation in the Olympics and higher intensity of sports disciplines were associated with higher mortality.

Little is known about the epidemiological characteristics of patients with coronavirus disease 2019 (COVID-19) in Japan. This is a retrospective observational study of COVID-19 patients; study was conducted from February 1 to May 31, 2020. We used publicly collected data on cases of COVID-19 confirmed by polymerase chain reaction (PCR) testing in Osaka Prefecture, Japan. We described the patient characteristics. The Cox proportional-hazards model was applied to evaluate the association between factors (sex, onset month, age group, city of residence) and mortality, and hazard ratios (HRs) with 95% confidence intervals were estimated. During the study period, 5.7% (1782/31,152) of individuals who underwent PCR testing for COVID-19 showed positive results. Among 244 patients with information on symptoms, the most common symptom was fever (76.6%), followed by cough (44.3%). Of the 1782 patients, 86 patients died. Compared with those aged 0–59 years, higher mortality was observed among those aged 60–69 years (HR: 12.02 [3.37–42.93]), 70–79 years (HR: 44.62 [15.16–131.30]), 80–89 years (HR: 68.38 [22.93–203.89]), and ≥90 years (HR: 144.71 [42.55–492.15]). In conclusion, in Osaka Prefecture, Japan, the most common symptom was fever, and older adults had higher mortality among COVID-19 patients.

Although the COVID-19 pandemic affects the emergency medical service (EMS) system, little is known about the impact of the COVID-19 pandemic on the prognosis of emergency patients. This study aimed to reveal the impact of the COVID-19 pandemic on the EMS system and patient outcomes. We included patients transported by ambulance who were registered in a population-based registry of patients transported by ambulance. The endpoints of this study were the incident number of patients transported by ambulance each month and the number of deaths among these patients admitted to hospital each month. The incidence rate ratio (IRR) and 95% confidence interval (CI) using a Poisson regression model with the year 2019 as the reference were calculated. A total of 500,194 patients were transported in 2019, whereas 443,321 patients were transported in 2020, indicating a significant decrease in the number of emergency patients transported by ambulance (IRR: 0.89, 95% CI: 0.88–0.89). The number of deaths of emergency patients admitted to hospital was 11,931 in 2019 and remained unchanged at 11,963 in 2020 (IRR: 1.00, 95% CI: 0.98–1.03). The incidence of emergency patients transported by ambulance decreased during the COVID-19 pandemic in 2020, but the mortality of emergency patients admitted to hospital did not change in this study.

Prior studies reported the association of reproductive factors with breast cancer (BC), but the evidence is inconsistent. We conducted a pooled analysis of nine cohort studies in Japan to evaluate the impact of six reproductive factors (age at menarche/age at first birth/number of births/age at menopause/use of female hormones/breastfeeding) on BC incidence. We conducted analyses according to menopausal status at the baseline or at the diagnosis. Hazard ratio (HR) and 95% confidence interval (CI) were estimated by applying Cox proportional‐hazards model in each study. These hazard ratios were integrated using a random‐effects model. Among 187,999 women (premenopausal: 61,113, postmenopausal: 126,886), we observed 873 premenopausal and 1,456 postmenopausal cases. Among premenopausal women, use of female hormones significantly increased BC incidence (HR: 1.53 [1.04–2.25]). Although P value for trend was not significant for age at first birth and number of births (P for trend: 0.15 and 0.30, respectively), women giving first birth at ages ≥36 experienced significantly higher BC incidence than at ages 21–25 years, and women who had ≥2 births experienced significantly lower BC incidence than nulliparous women. Among postmenopausal women, more births significantly decreased BC incidence (P for trend: 0.03). Although P value for trend was not significant for age at first birth and age at menopause (P for trend: 0.30 and 0.37, respectively), women giving first birth at ages 26–35 years experienced significantly higher BC incidence than at ages 21–25 years, and women with age at menopause: ≥50 years experienced significantly higher BC incidence than age at menopause: ≤44 years. BC incidence was similar according to age at menarche or breastfeeding history among both premenopausal and postmenopausal women. In conclusion, among Japanese women, use of female hormones increased BC incidence in premenopausal women, and more births decreased BC incidence in postmenopausal women.