Published papers

This study examines the effect of COVID-19 vaccination on political support by leveraging Japan's age-based vaccination rollout, which prioritized people aged 65 and older. Using a fuzzy regression discontinuity design, we found that vaccination increased favorable opinions of vaccination progress and infection control measures by 27.4% and 14.7%, respectively. These favorable opinions extended to positive perceptions of other infection control measures, ultimately fostering trust in the government. In addition, the effect of vaccination was heterogeneous: it was more pronounced among individuals with chronic diseases, women, those of lower socioeconomic status, and those with higher levels of interpersonal trust. In contrast, low trusters became more dissatisfied with how the Tokyo Olympics and Paralympics in 2021 were managed, without showing an increase in positive opinions of the government.

Background Social contact data in Japan have not been updated since 2011. The main objectives of this study are to report on newly collected social contact data, to study mixing patterns in the context of the COVID-19 pandemic, and to compare the contact patterns during and after mass events like the 2020 Olympic games, which were held in 2021. Methods We compared the number of contacts per day during and after the Olympic Games and on weekdays and weekends; we also compared them with a preCOVID-19 pandemic social contact study in Japan. Contact matrices consisting of the age-specific average number of contacted persons recorded per day were obtained from the survey data. Reciprocity at the population level was achieved by using a weighted average. Results The median number of contacts per day was 3 (interquartile range (IQR) = 1-6). The occurrence of the Olympic Games and the temporal source of data (weekday or weekend) did not change the results substantially. All three matrices derived from this survey showed age-specific assortative mixing patterns like the previous social contact survey. Conclusions The frequency of social contact in Japan did not change substantially during the Tokyo Olympic Games. However, the baseline frequency of social mixing declined vs those collected in 2011.

Studies show that the burden of caregiving tends to fall on individuals of low socioeconomic status (SES); however, the association between SES and the likelihood of caregiving has not yet been established. We studied the relationship between SES and the likelihood of adults providing long-term care for their parents in Japan, where compulsory public long-term insurance has been implemented. We used the following six comprehensive measures of SES for the analysis: income, financial assets, expenditure, living conditions, housing conditions, and education. We found that for some SES measures the probability of care provision for parents was greater in higher SES categories than in the lowest category, although the results were not systematically related to the order of SES categories or consistent across SES measures. The results did not change even after the difference in the probability of parents’ survival according to SES was considered. Overall, we did not find evidence that individuals with lower SES were more likely to provide care to parents than higher-SES individuals. Although a negative association between SES and care burden has been repeatedly reported in terms of care intensity, the caregiving decision could be different in relation to SES. Further research is necessary to generalize the results.

This study examines the effect of inheritance receipt on labor supply, exploring the empirical issues associated with inheritance expectations, informal caregiving, and liquidity constraints. The literature has not examined the possibility that ignoring the labor supply increase associated with the termination of caregiving can lead to an underestimation of the decrease in labor supply after inheritance. Based on a dataset of Japanese women, we found that inheritance decreased labor supply, primarily through changes in the extensive margin, particularly for recipients in their 50s and under 40 years of age with children. Unlike labor supply, household expenditures hardly change after an inheritance. Furthermore, unanticipated inheritances reduce labor supply compared to anticipated inheritances. Additionally, controlling for the termination of caregiving responsibilities resulted in a 25% larger estimate of the wealth effect of inheritance receipt on labor supply. Finally, pre-inheritance liquidity constraints have no effect on changes in labor supply.

This study examines the impact of reducing formal care benefits on the well-being of informal caregivers, contributing to the ongoing discourse about establishing sustainable and adequate levels of formal care. We utilize a reform introduced in Japan’s public long-term care insurance system, which curtailed formal care benefits for a group of recipients with low care needs. Employing a difference-in-difference approach with fixed effects on a nationally representative sample of coresident informal caregivers, we explore both the overall and temporal effects of this reform. Our findings reveal that the reform had an adverse impact on caregivers’ physical well-being, leading to diminished mobility and stability. The impact on caregivers’ mental well-being was less clear, reflecting a competing influence of stress and the psychological rewards associated with caregiving. The decline in physical well-being endured over time, while the effects on mental well-being were transient. Additionally, female caregivers exhibited greater vulnerability compared to their male counterparts, experiencing more significant deterioration in both physical and mental well-being. Alarmingly, the reform also negatively influenced the well-being of care recipients, suggesting that reducing formal care benefits does not yield positive outcomes for either caregivers or recipients. This study underscores the necessity of accounting for caregivers’ well-being when evaluating the cost-effectiveness of reducing formal care benefits and advocates for policies aimed at safeguarding female caregivers from health and financial challenges.

Using data from 17 countries, we investigate the effects of child marriage bans on child mortality in the next generation. We use within-country variation in mothers’ exposure to the ban across cohorts and in “treatment intensity,” calculated based on region-level child marriage prevalence and marriage age prior to the ban. We find that child marriage bans reduced under-5 mortality, with an effect of 19.7 percent corresponding to a one standard deviation change in treatment intensity. Increases in age at first marriage and first birth, which may have led to improved health-related decisions around the time of birth, appear to be the main drivers of the mortality reductions documented.

Objectives: We examined shifts in labor productivity and their economic ramifications among adult patients with long COVID in Japan. Methods: A total of 396 patients were categorized into three groups based on symptom progression: non-long COVID, long COVID recovered, and long COVID persistent. Patient-reported outcomes were assessed at three time intervals: 3, 6, and 12 months after COVID-19 diagnosis. Labor productivity was gauged through presenteeism and absenteeism, measured using the World Health Organization Health and Work Performance Questionnaire. Results: Long COVID was observed in 52.7% of patients, and 29.3% of all the patients continued to experience long COVID symptoms 1 year after diagnosis. At all three time points (3, 6, and 12 months after diagnosis), the long COVID persistent group showed a statistically significant difference in absolute presenteeism compared with the non-long COVID and long COVID recovered groups (P <0.01). Economic loss owing to decrease in labor productivity was calculated as $21,659 per year in the long COVID persistent group and $9008 per year in the long COVID recovered group (P <0.01). Conclusion: The study's results revealed a notable decline in labor productivity over time, underscoring the importance of early detection and intervention to mitigate the socio-economic repercussions of long COVID, in addition to its health implications.

This study examines the heterogenous effects of informal caregiving on caregivers' health and well-being and the mechanisms of the effects, which remain largely undiscussed in previous literature. We used a combined estimation of fixed effects and the instrumental variables to address unobserved time-invariant individual characteristics and the endogeneity problem between caregivers' health and caregiving status. Using data from the four waves of the Japanese Study of Aging and Retirement collected in 2007, 2009, 2011, and 2013, and covering individuals aged 50 to 75 at the baselines, we found robust evidence of the negative effects of informal caregiving on caregivers' mental health and life satisfaction, but not on their physical health. Regarding heterogenous effects, we found that informal caregiving adversely affected female but not male caregivers' mental health and life satisfaction. Our results also showed that informal caregiving had greater effects on individuals providing care for their mothers-in-law, with a higher socioeconomic status, living with their in-laws, and belonging to younger groups. Our results indicated that the loss of social networks and leisure and social activities were channels through which informal caregiving might negatively affect caregivers’ health and well-being. This study provides suggestions that policy makers may use to mitigate the negative effects of caregiving with targeted interventions, while formulating policies to support informal caregivers.

Although prior research has provided insights into the association between country-level factors and health inequalities, key research gaps remain. First, most previous studies examine subjective rather than objective health measures. Second, the wealth dimension in health inequalities is understudied. Third, a handful of studies explicitly focus on older adults. To bridge these research gaps, this study measures wealth-related inequalities in physical and cognitive impairments and examines the extent to which welfare states moderate wealth inequalities in physical and cognitive impairments among older people across Japan and Europe. We utilized harmonized data on non-institutionalized individuals aged 50–75 from the Japanese Study of Aging and Retirement (JSTAR) and the Survey of Health, Ageing and Retirement in Europe (SHARE) (N = 31,969 for physical impairments and 31,348 for cognitive impairments). Our multilevel linear regression analyses examined whether national public health spending and healthcare access resources explained cross-country differences in wealth inequalities in physical and cognitive impairments. We applied a concentration index to quantify the degree of wealth inequalities in impairments. The findings indicate that inequalities in both impairment outcomes favored wealthier individuals in all countries, but the magnitude of inequality varied by country. Furthermore, a higher share of public health spending, lower out-of-pocket expenditure, and higher investment in healthcare resources were associated with lower wealth inequalities, especially for physical impairments. Our findings suggest that different health interventions and policies may be needed to mitigate specific impairment inequalities.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly since 2019, and the number of reports regarding long COVID has increased. Although the distribution of long COVID depends on patient characteristics, epidemiological data on Japanese patients are limited. Hence, this study aimed to investigate the distribution of long COVID in Japanese patients. This study is the first nationwide Japanese prospective cohort study on long COVID. Methods: This multicenter, prospective cohort study enrolled hospitalized COVID-19 patients aged ≥18 years at 26 Japanese medical institutions. In total, 1200 patients were enrolled. Clinical information and patient-reported outcomes were collected from medical records, paper questionnaires, and smartphone applications. Results: We collected data from 1066 cases with both medical records and patient-reported outcomes. The proportion of patients with at least one symptom decreased chronologically from 93.9% (947/1009) during hospitalization to 46.3% (433/935), 40.5% (350/865), and 33.0% (239/724) at 3, 6, and 12 months, respectively. Patients with at least one long COVID symptom showed lower quality of life and scored higher on assessments for depression, anxiety, and fear of COVID-19. Female sex, middle age (41–64 years), oxygen requirement, and critical condition during hospitalization were risk factors for long COVID. Conclusions: This study elucidated the symptom distribution and risks of long COVID in the Japanese population. This study provides reference data for future studies of long COVID in Japan.

Introduction The rapid spread of COVID-19 posed a global burden. Substantial number of people died of the disease in the acute phase of infection. In addition, a significant proportion of patients have been reported to suffer from post-acute phase symptoms, sequelae of COVID-19, which may negatively influence the quality of daily living and/or socioeconomic circumstances of the patients. However, no previous study has comprehensively and objectively assessed the quality of life of patients by using existing international scales. Further, evidence of socioeconomic consequences among patients with COVID-19 is scarce. To address the multidimensional issues from sequelae of COVID-19, evidence from comprehensive surveys beyond clinical perspectives is critical that investigates health, and social determinants of disease progression as well as socioeconomic consequences at a large scale. Methods and analysis In this study, we plan to conduct a nationwide and comprehensive survey for the sequelae of COVID-19 in a total of 1000 patients diagnosed at 27 hospitals throughout Japan. This study will evaluate not only the health-related status of patients from clinical perspectives but also the Health-related Quality of Life (HRQoL) scores, socioeconomic status and consequences to discuss the sequelae of the disease and the related risk factors. The primary endpoint is the frequency of long-term complications of COVID-19 infection. The secondary endpoints are risk factors for progression to sequelae of COVID-19 infection. The study will provide robust and important evidence as a resource to tackle the issues from the sequelae of COVID-19 from the multi-dimensional perspectives. Ethics and dissemination This trial was approved by the Keio University School of Medicine Ethics Committee (20200243, UMIN000042299). The results of this study will be reported at a society meeting or published in a peer-reviewed journal.

Despite implementing no lockdowns and having a large elderly population, Japan had a low mortality rate due to COVID-19 compared to Europe and North America. The extent to which policies impacted person-to-person contact remains unclear. In this study, we examined changes in contact patterns and their association with behaviors and governmental recommendations in Japan during the pandemic. Ten social contact surveys were conducted between 2021 and 2023 reaching over 1500 participants per survey in Osaka and Fukuoka prefectures where governmental recommendations were first implemented due to high COVID-19 incidence. Their contact patterns were assessed through their demographic characteristics, COVID-19 vaccination status, and individual disease mitigation measures. Generalized linear models were used to identify factors associated with increased contacts. The mean number of contacts during the pandemic declined by at least 49.8% (8.2 weekday contacts and 6.0 weekend contacts per individual, adjusted by age and sex) compared to a study conducted prior to 2020. Weekdays, occupation, larger household sizes, and mask wearing were associated with a higher number of contacts. The frequency and duration of contacts were negatively associated with the issuance of COVID-19 governmental measures, yet the relative change in contacts was not as prominent as pre- and post-lockdown situations in the United Kingdom. There was a gradual increase in contacts with time and less strict public health recommendations. Yet, contacts that did not increase with uptake of COVID-19 vaccination and continuous mask wearing depict cautious behavior across the survey population during the pandemic and into 2023. These results are in contrast with European countries where contacts largely increased among vaccinated individuals compared to the non-vaccinated. Social contacts are country and context specific, highlighting the need for data collection across different communities.

Objective: We aimed to determine how municipal subsidies for seasonal influenza vaccines for the elderly affected vaccination coverage and health outcomes and how responses to vaccine prices changed during the COVID-19 pandemic. Study design and methods: This ecological study includes 1245 municipalities in Japan between 2019 and 2020. Fixed-effects regression analysis was performed to evaluate the effect of influenza vaccine cost subsidy for people aged 65 years or older on vaccination coverage, all-cause mortality, and influenza-related mortality. Results: The vaccination rate increased when patients' copayments decreased, and reducing the copayment by 1000 Japanese Yen (JPY) was estimated to increase the vaccination rate by 6.3% (95% confidence interval [CI] 4.5–8.2%) in the adjusted model. When examining the additional effect of a zero price compared to a nearly zero price, we found that a zero price increased the immunization rate by 6.4% (95% CI 1.4–11.5%). The effect of copayment on the increase in vaccination coverage was significantly lower during the pandemic than in the pre-pandemic period. The municipal and prefectural analyses found no association between influenza vaccine copayments and all-cause, influenza, or pneumonia mortality. Conclusion: Cost subsidies and the zero-price effect were shown to increase vaccination coverage but were not associated with relevant mortality measures. Although the impact was attenuated under pandemic conditions, cost subsidy effectively increases the vaccination rate.

Background: Health inequity in relation to COVID-19 infection and socioeconomic consequences is a major global concern. Mental health issues in vulnerable populations have received special attention in research and practice during the COVID-19 pandemic. However, there is limited evidence on the nature of the anxieties experienced as a result of COVID-19, and how such concerns vary across demographic groups. Aim: This study examines anxiety among the working population of Japan (aged 18–59), in terms of both COVID-19 infection and socioeconomic consequences, using an internationally validated tool, the Pandemic Anxiety Scale (PAS). Methods: Data were collected using an online survey (n = 2,764). The analyses included an exploratory factor analysis (EFA), a confirmatory factor analysis (CFA), and structural equation modeling (SEM), followed by validation of the Japanese version of the PAS. Results: A two-factor latent variable model shows the multidimensionality of anxiety in regard to the COVID-19 pandemic and the disparity across population groups in predicting the two defined anxiety dimensions. Several path coefficients showed somewhat unexpected and/or unique results from Japan compared with previous European studies. Specifically, self-reported health status was not significantly related to disease anxiety, and those who were not in paid employment reported lower consequence anxiety. The SEM results showed a greater number of significant exogenous variables for consequence anxiety compared to disease anxiety, highlighting disparities in pandemic anxiety by socioeconomic status in regard to socioeconomic consequences of the pandemic. Conclusion: In contrast to existing European studies, evidence from the current study suggests contextual patterns of health inequity. Due to the prolonged socioeconomic consequences of the pandemic, multidisciplinary research on mental health issues and the quality of life remains an important research agenda in exploring socioeconomic measures in context, towards addressing inequity concerns.

Studies indicate that mortality increases after income receipt. To explore whether this is due to increased economic activity around the period of receiving income, we examine within-month patterns in ambulance transport incidents, focusing on location and timing. Using Japan's National Pension payments made every two months, we compare the number of ambulance transport incidents on the day of pension payment and on surrounding days in payment months with those in non-payment months. The results show a 4.5% increase in ambulance transport incidents on the day of pension payment, linked to increased activities such as gambling, shopping, and dining out. We show suggestive evidence that income receipt boosts economic activities by the mechanism of easing liquidity constraints. These findings have implications for healthcare system preparedness and the optimal design of public benefit payment.

We leverage the introduction of Vietnam's primary compulsory schooling law as a natural experiment to provide new evidence on the effects of parents’ education on child mortality. Employing data from the 2009 Vietnam Population and Housing Census and a regression discontinuity design, we show that the reform increased average schooling duration by approximately half a year. Our key findings reveal that one additional year of maternal schooling induced by the law reduced child mortality by 29.4%, with the majority of improvements concentrated among women residing in rural areas, minor ethnicities, and female children. While increased paternal education also exhibited a negative impact on child mortality, the effect diminished in magnitude and became statistically insignificant when controlling for maternal education. This suggests that neglecting to account for spousal education does not introduce substantial biases in estimates of maternal education's effect on child mortality but may lead to an upward bias in estimates for fathers’ education. Further, our results indicate that increased maternal education was associated with increasing age at marriage and first birth, reducing total fertility, and engaging more in paid work, all of which could serve as potential pathways for child mortality reduction.

Objective To characterise the optimal targeting of age and risk groups for COVID-19 vaccines. Design Motivated by policies in Japan and elsewhere, we consider rollouts that target a mix of age and risk groups when distributing the vaccines. We identify the optimal group mix for three policy objectives: reducing deaths, reducing cases and reducing severe cases. Setting Japan, a country where the rollout occurred over multiple stages targeting a mix of age and risk groups in each stage. Primary outcomes We use official statistics on COVID-19 deaths to quantify the virus transmission patterns in Japan. We then search over all possible group mix across rollout stages to identify the optimal strategies under different policy objectives and virus and vaccination conditions. Results Low-risk young adults can be targeted together with the high-risk population and the elderly to optimally reduce deaths, cases and severe cases under high virus transmissibility. Compared with targeting the elderly or the high-risk population only, applying optimal group mix can further reduce deaths and severe cases by over 60%. High-efficacy vaccines can mitigate the health loss under suboptimal targeting in the rollout. Conclusions Mixing age and risk groups outperforms targeting individual groups separately, and optimising the group mix can substantially increase the health benefits of vaccines. Additional policy measures boosting vaccine efficacy are necessary under outbreaks of transmissible variants.

A characteristic that differentiates vaccination from other health behaviors is that it is a public good. By the nature of a public good, negative peer effects are expected when determining vaccination behavior for free-rider incentives. This study empirically analyzes whether the surrounding vaccination status in a community influences individual vaccination behavior using administrative data on influenza vaccination for all the older people within a city of Japan. We first employ fixed effect analysis with a lagged dependent variable. We then examine how vaccination behavior changes in the event of the loss of a cohabitant and how this effect interacts with the community peer effect. Our estimation results confirm positive peer effects: the higher the community's vaccination rate, the more the raising effect of the individual's vaccination rate.