Differences in Sensitivity Between the Japanese and Z Score Criteria for Detecting Coronary Artery Abnormalities Resulting from Kawasaki Disease.

No studies have assessed differences between the Japanese and Z score criteria in the echocardiographic detection sensitivity of coronary artery (CA) abnormalities using large-scale data containing samples from multiple facilities engaged in daily clinical practices of Kawasaki disease (KD). We analyzed data from the 25th Japanese nationwide KD survey, which identified 30,415 patients from 1357 hospitals throughout Japan during 2017-2018. Hospitals were classified according to their use of Z score criteria. We assessed differences in hospital and patient background factors and compared the prevalence of CA abnormalities among groups using the Z score criteria. Multivariable logistic regression analyses were performed to evaluate differences in the detection sensitivity for CA abnormalities. The Z score criteria were more likely to be utilized in larger hospitals with more pediatricians and cardiologists. Even after controlling for potential confounders, detection sensitivities by the Z score criteria were significantly higher than by the Japanese criteria in patients with CA dilatations (adjusted odds ratio (95% confidence interval) 1.77 (1.56-2.01)) and aneurysms (1.62 (1.17-2.24)). No significant difference was found in patients with giant CA aneurysms. Compared with the Japanese criteria, the Z score criteria were significantly more sensitive for detecting patients with CA dilatations regardless of age, and for those with CA aneurysms only in patients aged ≤ 1 year. Our results indicate that differences in the detection sensitivity for CA abnormalities between the Z score and the Japanese criteria were dependent on the CA size and patient age.

Follow up of Kawasaki disease based on nationwide survey data in Japan: Mortality among those with a history of Kawasaki disease in Japan: Results of a 30-year follow up: Mortality among those with a history of Kawasaki disease in Japan: Results of a 30-year follow up.

BACKGROUND: The long-term prognosis of those with a history of Kawasaki disease (KD) is still unknown. METHODS: Using a permanent registry system in Japan (koseki), 6,576 persons with a history of KD were followed up. The average follow-up period was 30 years. The endpoint was death. RESULTS: With a 99.5% follow-up rate, 68 deaths (48 males and 20 females) were observed. The overall standardized mortality ratio, of which reference was vital statistics in Japan, was not elevated. However, the observation according to the presence or absence of cardiac sequelae showed that the standardized mortality ratio for those with cardiac sequelae significantly elevated. Nine persons, all of whom were males, died of KD (including those cases where KD was suspected), but all deaths occurred in individuals who were under 30 years of age. CONCLUSIONS: This study revealed the long-term prognosis for KD, but almost all participants were younger than 40 years. Continuing follow up of this cohort is required to clarify whether a history of KD relates to the development of atherosclerosis when participants become middle aged or older.

Epidemiology and Risk Factors for Giant Coronary Artery Aneurysms Identified After Acute Kawasaki Disease.

A giant coronary artery (CA) aneurysm is a potentially fatal cardiac complication resulting from Kawasaki disease (KD). We aimed to identify epidemiologic characteristics and potential risk factors associated with giant CA aneurysms identified after acute KD. We analyzed 90,252 patients diagnosed with KD from 2011 to 2018, using data obtained in nationwide KD surveys conducted in Japan. Multivariable logistic regression analyses were performed to evaluate potential risk factors associated with subsequent giant CA aneurysm complications (defined as lumen size ≥ 8 mm), adjusting for all potential factors. Giant CA aneurysms were identified in 144 patients (0.16%) after acute KD. The annual prevalence ranged from 0.07 to 0.20% during the study period. In the multivariate analyses, male sex (adjusted odds ratio 2.09 [95% confidence interval 1.41-3.11], recurrent KD (1.90 [1.09-3.33]), IVIG administration at 1-4 days of illness (1.49 [1.04-2.15]) and ≥ 8 days after KD onset (2.52 [1.38-4.60]; reference, 5-7 days), detection of CA dilatations and aneurysms at initial echocardiography (4.17 [1.85-5.41] and 46.5 [28.8-74.8], respectively), and resistance to IVIG treatment (6.09 [4.23-8.75]) were significantly associated with giant CA aneurysm complications identified after acute KD. The annual prevalence of giant CA aneurysms identified after acute KD did not increase during the study period. Patients with larger CA abnormalities detected at initial echocardiography were independently associated with progression to giant CA aneurysm complications after acute KD regardless of the number of days from onset at treatment initiation.

Outcomes in Kawasaki disease patients with coronary artery abnormalities at admission.

BACKGROUND: Previous studies demonstrated that coronary artery lesions (CALs) resulting from Kawasaki disease (KD) can improve over time. However, limited information is available on sub-acute outcomes of CALs detected at admission during KD illness. METHODS: The nationwide Japanese KD survey contained substantial information on KD patients with CALs detected at admission and who received standard IVIG treatment within 10 days of disease onset. Coronary outcomes were evaluated by changes in CALs from admission to the first assessment at 30 days from disease onset in three categories: improved, unchanged, and progressed. Ordinal logistic regression analysis was performed to evaluate factors associated with the outcomes. RESULTS: Of 2024 patients with CALs detected at admission, improved, unchanged, and progressed outcomes were found in 1548 (76.5%), 390 (19.3%), and 86 (4.2%), respectively. Over 80% of patients with coronary artery (CA) dilatations had improved outcome. Independent factors associated with worse outcomes were larger-size CALs (adjusted ORs [95% CIs]: CA aneurysm = 5.13 [3.65-7.22] and giant CA aneurysms = 7.49 [3.56-15.72] compared with CA dilatation, respectively), age ≥ 60 months (1.45 [1.08-1.94] compared with 12-59 months), recurrent KD (1.57 [1.07-2.29]), parental history of KD (2.23 [1.02-4.85]), and delayed admission (8-10 days from disease onset: 1.76 [1.21-2.57] compared with 1-4 days). CONCLUSIONS: KD patients with larger CALs, ≥60 months old, and with recurrent status or parental history may require more rigorous treatment. In addition, delayed admission may result in worse coronary outcome, indicating that prompt diagnosis and treatment are required.

Epidemiology, Treatments, and Cardiac Complications in Patients with Kawasaki Disease: The Nationwide Survey in Japan, 2017-2018.

OBJECTIVE: To report the epidemiologic characteristics, treatments, and cardiac complications of Kawasaki disease, using data from the nationwide survey in Japan. STUDY DESIGN: The nationwide Kawasaki disease survey in Japan has been conducted biennially since 1970. The most recent survey was completed in 2019, obtaining information for patients who developed Kawasaki disease during 2017-2018. Survey respondents were hospitals specializing in pediatrics and those with ≥100 beds and a pediatric department throughout Japan, where patients with Kawasaki disease were eventually hospitalized. RESULTS: The survey identified 32 528 patients with Kawasaki disease, which consisted of 15 164 (46.6%) in 2017 and 17 364 (53.4%) in 2018. The highest annual incidence rate was recorded in 2018 (359 per 100 000 children aged 0-4 years). After 1982, patients with ≤4 principal Kawasaki disease signs gradually increased, resulting in 6847 (21.1%) patients diagnosed during 2017-2018. Among the 30 784 patients receiving initial intravenous immunoglobulin administration, 6061 (19.7%) did not respond. Within 30 days of Kawasaki disease onset, 9.0% of patients were diagnosed with cardiac complications, and 2.6% of patients developed cardiac sequelae after the acute illness. CONCLUSIONS: The annual number of patients developing Kawasaki disease in Japan increased from 1970 through 2018, whereas the proportion of patients with Kawasaki disease with cardiac complications decreased in the most recent 2 decades. Early diagnosis of Kawasaki disease as well as advances in initial treatments could explain these findings.

Cumulative incidence of Kawasaki disease with cardiac sequelae in Japan.

BACKGROUND: Some patients with Kawasaki disease (KD) develop cardiac sequelae, which increase the risk of subsequent ischemic heart events. Knowing the cumulative incidence (CI) of KD with cardiac sequelae may contribute to developing health policies to prevent subsequent ischemic events in these patients. METHODS: Study participants consisted of 254 984 patients aged 0-9 years with KD who were registered in nationwide surveys in Japan from 1991-2016. We calculated the incidence probabilities by dividing the number of patients with KD aged 0-9 years by the population used in vital statistics of each calendar year. We calculated the cumulative proportion of those not affected by KD, by multiplying each probability in patients aged from age 0-9 years. The CI of KD was obtained by subtracting this value from 1. We also calculated the number of patients in each birth cohort (BC). The same was done to calculate the CI of KD-related cardiac sequelae. RESULTS: The CIBC steadily increased from 0.005067 in males and 0.003668 in females in 1991 to 0.011431 in males and 0.0088253 in females in 2007. The CIBC of KD with cardiac sequelae decreased from 0.000478 in males and 0.000213 in females in 1997 to 0.000339 in males and 0.000169 in females in 2007. CONCLUSION: The increasing CIBC of KD indicates an increased susceptibility to KD in accordance with birth year. The decreasing CIBC of cardiac sequelae suggests the efficacy of KD treatment.

Nationwide epidemiologic survey of Kawasaki disease in Japan, 2015-2016.

BACKGROUND: Approximately 50 years have passed since Kawasaki disease (KD) was first reported. The KD nationwide survey began in 1970. Although >360 000 cases have already been reported in Japan, the cause is still unknown. In Japan, the number of patients and incidence rate of KD has continued to increase. It is necessary to examine the trend of the occurrence in the surveillance of KD. METHODS: The nationwide survey of patient incidence in 2015 and 2016 was conducted in 2017, as the 24th nationwide survey of KD. A questionnaire was sent to pediatric departments in hospitals with >100 beds and specialized pediatric hospitals, and was responded to by the attending pediatricians. RESULTS: The total number of patients in 2 years was 31 595, and the sex ratio (male/female) was 1.34. The incidence rate (/100 000 children aged 0-4 years/year) was 330.2 (371.2 in boys, 287.3 in girls) in 2015, and 309.0 (343.2 in boys, 273.2 in girls) in 2016. The number of patients by month peaked in January. The age-specific incidence rate according to sex was highest in children between 9 and 11 months of age, after which the incidence rate gradually decreased with advancing age. CONCLUSIONS: We summarize the most recent nationwide survey of KD and consider the change in the epidemiologic picture.

Seasonality of i.v. immunoglobulin responsiveness in Kawasaki disease.

BACKGROUND: Evidence suggests that seasonal variation in the onset of Kawasaki disease (KD) exists worldwide. Whether a seasonal component to successful i.v. immunoglobulin (IVIG) therapy exists in KD-positive children, however, is unknown. We addressed this question by focusing on patients with primary onset KD who were non-responsive to IVIG treatment, in the large nationwide Japanese KD survey datasets from 2009 to 2016. METHODS: In these datasets, the IVIG therapy non-responders were defined as patients whose fever persisted ≥24 h or recurred ≤24 h after the end of the initial IVIG treatment (dosage, 2,000 mg/kg). Those who successfully responded to this treatment were defined as IVIG responders. The consecutive monthly trend of the proportion of IVIG non-responders was analyzed throughout the study period to investigate seasonal periodicity on Fourier analysis, and the monthly distributions of non-responders and responders were compared. RESULTS: From a total of 113 691 KD-positive patients, 15.7% were IVIG non-responders, and 61% were male. The proportion of non-responders increased across each calendar year with fluctuation, and Fourier analysis indicated seasonal periodicity. The seasonality effect differed between responders and non-responders, with the proportion of responders tending to increase in autumn through winter, while the non-responders showed a decreasing trend in autumn. The seasonality effect tended to differ by sex. CONCLUSIONS: The results indicate that the currently unknown etiological agents of KD might differ between IVIG responders and non-responders. In addition, immune reactivity against such agents possibly differs by sex in the IVIG non-responders.

An 18-Year Follow-up Survey of Dioxin Levels in Human Milk in Japan.

BACKGROUND: Globally, few published studies have tracked the temporal trend of dioxin levels in the human body since 2000. This study describes the annual trend of dioxin levels in human breast milk in Japanese mothers from 1998 through 2015. METHODS: An observational study was conducted from 1998 through 2015. Participants were 1,194 healthy mothers following their first delivery who were recruited annually in Japan. Breast milk samples obtained from participants were analyzed using gas chromatography and mass spectrometry for dioxins, including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs). RESULTS: Mean age was 29.5 years, and 53% of participants were 20-25 years old. A declining trend in total dioxin levels was found, from a peak of 20.8 pg toxic equivalence (TEQ)/g fat in 1998 to 7.2 pg TEQ/g fat in 2014. Data from the last 5 years of the study indicated a plateau at minimal levels. In contrast, an increasing trend was found in the mean age of participants during the last 5 years. Although significantly higher dioxin levels were observed in samples from older participants, an upward trend in dioxin levels was not observed, indicating that dietary and environmental exposure to dioxins had greatly diminished in recent years. CONCLUSIONS: Dioxin levels in human breast milk may be approaching a minimum in recent years in Japan. The findings may contribute to global reference levels for environmental pollution of dioxins, which remains a problem for many developing countries.

Suicidal patients presenting to secondary and tertiary emergency departments and referral to a psychiatrist: a population-based descriptive study from Japan.

BACKGROUND: In Japan, although many suicidal studies were previously conducted in tertiary emergency department (ED) settings, no published studies have reported on suicidal patients presenting to the secondary EDs. The aim of the study was to describe the characteristics of suicidal patients and the referral rates to a psychiatrist overall and by type of facility. METHODS: Questionnaires were sent to all secondary and tertiary EDs in Tochigi prefecture, Japan. Data were collected for cases who presented in September 2009. Chi-square, Fisher's exact, and t-tests compared the results by gender and type of ED. RESULTS: All 74 EDs responded to the survey. There were 81 patients who attempted or died by suicide (36 men and 45 women). The most common method of suicide attempt was drug overdose (57%) followed by stabbing (17%). About a half used prescription drugs to attempt or die by suicide. The majority had a history of psychiatric disorders, and 35% had previous suicide attempt. About a half were admitted to medical or surgical unit; 33% were discharged home; and 9% died. After excluding those who died, 53% were referred to a psychiatrist, but 47% were not referred to a psychiatrist. The referral rate was lower for cases seen at secondary EDs (38%) compared to tertiary EDs (67%). CONCLUSION: Although professional organizations suggest that suicidal patients are seen by a psychiatrist, many were not, especially at secondary EDs. Further research is needed to assure that suicidal patients presenting to EDs receive appropriate psychiatric assessment and follow-up after discharge.

Epidemiological observations of Kawasaki disease in Japan, 2013-2014.

BACKGROUND: The etiology of Kawasaki disease (KD) is unknown. In Japan, the number of patients and incidence rate of KD has increased continuously since its discovery. The aim of this report was to analyze the latest nationwide epidemiological survey of KD in Japan. METHODS: The 23rd nationwide survey of KD was conducted in 2015. To report on all patients diagnosed with KD in 2013 and 2014, a questionnaire was sent to hospitals with ≥100 beds containing pediatric departments, as well as specialized pediatric hospitals. RESULTS: The number of KD patients reported was 15 696 in 2013 and 15 979 in 2014, resulting in an annual incidence rate of 302.5 and 308.0 per 100 000 population aged 0-4 years, respectively. The number of patients and incidence rate of KD in 2014 were the highest ever recorded in Japan. The number of patients diagnosed per month peaked in January, and a gradual increase in summer was also observed. Eight patients died of KD in 2013 and 2014. CONCLUSIONS: The number of patients and incidence rate of KD in Japan continue to increase. Continued surveillance of epidemiological trends of KD is therefore required.

Cumulative incidence of Kawasaki disease in Japan.

BACKGROUND: Although the incidence rates of Kawasaki disease (KD) in Japan have been determined in nationwide surveys, the cumulative incidence, that is, the proportion of those with a history of KD in the general population of 10-year-olds, is currently unknown. The aim of this study was therefore to assess the cumulative incidence of KD in Japan. METHODS: Using the age- and sex-specific incidence rate of KD in Japan from the results of the nationwide surveys, incidence probabilities, that is, the age-specific number of KD patients divided by the population used in the vital statistics, and cumulative proportions of those not affected by KD up to the end of 9 years of age, were calculated. The cumulative incidence was then defined as 1 minus the cumulative proportion. The observed age classes were 0, 1, 2, 3, 4, and 5-9 years. All data were calculated by sex. RESULTS: The cumulative incidence was 0.004833 for boys and 0.003474 for girls in 1991, but was 0.015284 and 0.012145 in 2014, respectively. According to these figures, 15.284 per 1,000 boys and 12.145 per 1,000 girls have been affected by KD by the age of 10 years. The birth-cohort cumulative incidences had similar trends. CONCLUSIONS: More than 10 persons in 1,000 have a history of KD at age 10 years in Japan.

[Self-reported obituary columns in a local daily newspaper].

Objectives　To reveal the features of death and subsequent funeral services, we analyzed self-reported obituaries in The Shimotsuke, a local daily newspaper in Tochigi, Japan. In addition, the usefulness and disadvantages of such a database of deaths based on the obituaries were discussed.Method　For a 5-year period, from January 2011 through December 2015, all the obituary columns in The Shimotsuke were computerized as a database and analyzed. Some results were compared with the vital statistics data in the corresponding period of time. Data analyzed were: dead persons' address (municipalities), name, sex, cause of death, age at death, date of death and funeral services, the chief mourner (Moshu), and so on.Results　During the observed 5-year period, 69,793 deaths appeared in the columns, which were 67.6% of the all deaths in the vital statistics. No difference was observed in the proportions between the sexes in the published deaths in comparison with the vital statistics. In both sexes, the proportion was low in 0-9 years old, then high among 10-19 years, decreasing in 20s, and after then the proportion increased according to the age. The proportion was low in city areas, such as Utsunomiya and Oyama, and high in some cities and towns in the northern or eastern parts of Tochigi prefecture. The highest was in Motegi Town (88.0%), and the lowest was Nogi Town (38.0%), which is located in the southern-most part of the prefecture and is closest to the Tokyo metropolitan area. Almost all the funeral services were conducted within a week of the death, and no delays were observed to have been caused by the short supply of cremation services, which exists in large cities in Japan. In case where the chief mourner was a child, a parent, or a spouse of a child, the male sex was dominant. Analyses of death from senile decay, suicide, and homicide indicated that the accuracy of the published cause of death was low. The date of the funeral services was strongly influenced by superstitions in this country.Conclusions　Observations of the self-reported obituaries in a local daily newspaper over five years revealed the situations of the deaths in the area that could not be observed using vital statistics. Despite limitations, the information was partially useful as a database.

[ESTIMATED NUMBER OF PATIENTS WITH FOOD ALLERGY IN JAPAN: THE PRESENT STATUS AND ISSUES REGARDING EPIDEMIOLOGICAL INVESTIGATION].

BACKGROUND: The number of patients with food allergy in Japan is increasing year by year, although the precise prevalence of them is not clear. We aimed to determine the estimated number of people with food allergies in Japan and produce new methods of the investigation of them. METHODS: We determined the number of people with food allergies using government data and statistics such as demographic statistic and the number of students. RESULTS: In infants, the number of patients with a food allergy was 800000 as per the self-reported prevalence; however, as per the physician's diagnoses, 300000-500000 of them had a food allergy. In students, the selfreported number was 600000, while 350000 cases were diagnosed by physicians. In adults, the consumer agency investigated the patients who visited the hospital with the immediate hypersensitivity. In this study, the participants were limited to patients who visited the hospital. This made the estimation of the overall prevalence of food allergy in Japan. CONCLUSION: For children, if we add the questionnaire to the existing study, which questions them regarding the symptoms of food allergy, the diagnosis by the physician, and the blood test, we can better investigate the prevalence of food allergies and changing pattern by the year. In adults, we propose that future investigations consisting of the National Health and Nutrition Survey and a comprehensive survey of living conditions should be conducted, because few studies have reported on food allergies.

Difference in Risk Factors for Subtypes of Acute Cardiac Lesions Resulting from Kawasaki Disease.

Few studies discuss the risk factors for acute cardiac lesions (within 30 days) resulting from Kawasaki disease (KD). We aimed to clarify the characteristics of patients with cardiac lesions within 30 days and determine the risk factors for acute cardiac lesion subtypes. Using the 23rd nationwide survey of KD in Japan, we analyzed data from patients with or without acute cardiac lesions resulting from KD (n = 31,380). We subdivided patients with acute cardiac lesions into three types: acute valvular lesions, coronary aneurysms, and giant coronary aneurysms (GCA), and calculated the odds ratios of potential risk factors for acute cardiac lesion subtypes. The prevalence of acute cardiac lesions was 8.6%, and these lesions were more prevalent among males than females (1.98:1). Male sex, age <1 year, and atypical definite cases predicted coronary artery lesions (CAL). The risk factors for valvular lesions differed from the risk factors for CALs, but GCA risk factors were similar to CAL risk factors: age <1 year, later presentation to hospital, atypical definite cases, and resistance to initial intravenous immunoglobulin (IVIG) therapy. Resistance to IVIG therapy was a significant risk factor for acute GCA. We found differences in cardiac lesion risk factors within 30 days of diagnosing KD between acute CAL and valvular lesions resulting from KD. In particular, pediatricians should consider atypical definite cases and resistance to initial IVIG when assessing the risk of acute-phase GCA.

Temporal and geographical clustering of Kawasaki disease in Japan: 2007-2012.

BACKGROUND: Since 1987, no study has reported the municipal-level geographical clustering of Kawasaki disease (KD) in Japan. Therefore, the aim of the present study was to identify the temporal and municipal-level geographical clustering of KD. METHODS: The annual incidence rates of KD for each municipality were calculated using nationwide data from 73 758 patients with KD (2007-2012). To determine whether temporal and municipal-level clustering existed, we calculated the correlations of the annual incidence rates for each municipality during the study years, and compared these rates with those of the adjacent municipalities. Spatial scanning analysis was used to identify the geographical clusters for each year, and the incidence rates in those clusters were compared with the rates in the surrounding region. RESULTS: The annual national incidence rate of KD, adjusted for the prefecture-specific response rate, was 322.45 patients per 100 000 children aged 0-4 years. The correlation between the annual incidence rates during 2 consecutive years was significantly positive (coefficients, 0.149-0.428). On spatial scanning analysis, the most likely clusters were in the Tokyo metropolitan area during 2007-2010 and 2012, and in Kumamoto prefecture during 2011. CONCLUSION: Kawasaki disease exhibits temporal and municipal-level clustering.

Time course of cardiac lesions due to Kawasaki disease in Japan: 22nd nationwide survey (2011-2012).

BACKGROUND: Although Kawasaki disease (KD) cardiac lesions can be treated with i.v. immunoglobulin (IVIG) and are associated with age and sex, the time course of cardiac lesions remains unclear on the large scale. METHODS: We used the data of the 22nd nationwide survey of KD in Japan (2011-2012). We divided the time course of cardiac lesions into eight groups according to the combination of timing (first visit to hospital, acute phase, and sequelae) and presence of cardiac lesions (E, existence of cardiac lesions; N, non-existence of cardiac lesions): EEE, EEN, ENE, NEE, ENN, NEN, NNE, and NNN. For example, EEN shows that cardiac lesions existed at first visit to hospital and in the acute phase, but did not exist as sequelae. A total of 24 952 patients were analyzed. RESULTS: The majority (90.6%) of patients belonged to the NNN group, followed by the EEN (3.21%) and NEN (3.33%) groups. Male sex and ages ≤5 months and ≥5 years tended to be more prevalent. Non-response to initial IVIG therapy was the most prevalent in all groups other than NNN. CONCLUSIONS: The time course of cardiac lesions and the relationship with sex, age, and IVIG therapy have been described. KD patients who are male, aged ≤5 months or ≥5 years, and non-responders to initial IVIG tend to have cardiac lesions at some point in the time course of KD.

Descriptive epidemiology of Kawasaki disease in Japan, 2011-2012: from the results of the 22nd nationwide survey.

BACKGROUND: The number of patients and incidence rate of Kawasaki disease (KD) are increasing in Japan. We have therefore characterized the latest epidemiological information on KD. METHODS: The 22nd nationwide survey of KD, which targeted patients diagnosed with KD in 2011 and 2012, was conducted in 2013 and included a total of 1983 departments and hospitals. In order to report on all patients with KD during the 2 survey years, we targeted hospitals of 100 beds or more with pediatric departments, or specialized pediatric hospitals. RESULTS: From a total of 1420 hospitals and departments (71.6% response rate), 26,691 KD patients were reported (12,774 in 2011 and 13,917 in 2012; 15,442 males and 11,249 females). The annual incidence rates were 243.1 per 100,000 population aged 0 to 4 years in 2011 and 264.8 in 2012. The number of cases of KD recorded in 2012 was the highest ever reported in Japan. The incidence rate of complete cases was also the highest ever reported in Japan and contributed to the increase in the rate of total cases in recent years. The number of patients diagnosed per month peaked in January, and additional peaks were noted during summer months, although these peaks were lower than those seen in winter. Age-specific incidence rate showed a monomodal distribution with a peak in the latter half of the year in which patients were born. CONCLUSIONS: The number of patients and the incidence rate of KD in Japan continue to increase. A similar trend has also been seen for patients with complete KD.

Incidence of Kawasaki Disease Before and After the COVID-19 Pandemic in Japan: Results of the 26th Nationwide Survey, 2019 to 2020.

Importance: Global studies have reported that the incidence of Kawasaki disease (KD) declined during the COVID-19 pandemic. These studies suggest that the global pandemic and its accompanying mitigation measures may provide an important opportunity to explore the hypothesis of a KD pathogenesis. Objective: To compare changes in KD incidence in Japan before and after the start of the COVID-19 pandemic. Design, Setting, and Participants: This cohort study was conducted using the data set from Japan's 26th nationwide KD survey that obtained information on patients who were diagnosed with KD in Japan from January 1, 2019, through December 31, 2020. Main Outcomes and Measures: Kawasaki disease incidence rates were calculated by referring to the national population data in the vital statistics data for Japan. Results: A total of 28 520 patients were identified (16 236 male individuals [56.9%]; median [IQR] age, 26 [14-44] months). A total of 17 347 patients were diagnosed with KD in 2019 and 11 173 were diagnosed in 2020, representing a 35.6% reduction in the number of patients diagnosed in 2020 compared with the previous year. Patient distributions for days of illness at the first hospital visit were almost identical in 2019 and 2020, suggesting that the decrease in KD incidence likely was not associated with pandemic-related delays in seeking treatment. The proportion of patients diagnosed with KD who were younger than 12 months was significantly larger in 2020 than in 2019 (21.6% vs 19.4%; P < .001). Compared with KD incidence among younger patients, the incidence among those 24 months and older declined rapidly after initiation of COVID-19 special mitigation measures, with a greater percentage reduction (58.3% reduction in July), but rebounded faster after the end of the special mitigation period. By contrast, the incidence among patients younger than 12 months declined moderately after the initiation of the special mitigation period, with a lower percentage reduction (40.3% reduction in October), and rebounded at a later phase. Conclusions and Relevance: In this cohort study, the number of patients diagnosed with KD decreased by approximately one-third across Japan in 2020, with no indication that parents avoided a hospital visit. Differences in KD incidence reduction patterns before and after the initiation of COVID-19 pandemic mitigation measures were found in patients with KD aged younger than 12 months compared with those 24 months or older, suggesting a potential KD pathogenesis involving transmission among children.