Main findings of this study
In this study, we conducted a descriptive-epidemiological study using Joinpoint regression analysis to examine changes in suicide rates by prefectural levels of rurality and deprivation in Japan from 2009 to 2022. The results showed that suicide rates in Japan for both men and women at different levels of rurality and deprivation remained roughly parallel during the research period. For both men and women, suicide rates at all levels of rurality and deprivation were on a downward trend until around 2019, just before the onset of the pandemic. And then, suicide rates in women showed a clear upward trend, while the trend in suicide rates of men also changed around 2019, with a slightly increasing or flat trend thereafter. For men, there were differences in suicide rates according to levels of rurality and deprivation, with suicide rates higher at higher levels of rurality and deprivation, although the differences in suicide rates were smaller in 2022 than in 2009. For women, on the other hand, there was little difference in suicide rates by levels of rurality and deprivation in 2022.
Changes in suicide rates before and after the onset of the COVID-19 pandemic
The study examined trends in suicide rates broken down by gender, age, rurality and deprivation, and found that in most categories, around 2019 (the joinpoint was 2019 or the 95%CI for the joinpoint included 2019), the trend in suicide rates changed. That is, suicide rates were on a downward trend in all categories until about 2019, after which rates began to increase, level off, or the downward trend was mitigated. A previous study pointed to a marked change in suicide rates in Japan after 2020 compared to earlier years due to the COVID-19 pandemic [9], and the results of this study are also consistent with these results. However, not all groups by gender, age, rurality and deprivation had a trend change around 2019 in this study. There was a joinpoint in 2017 for some groups, but the 95% CI did not include 2019. This may indicate that changes in suicide rate trends were occurring in certain groups prior to the pandemic. Alternatively, it is possible that the joinpoint regression analysis used in this study could not have estimated the exact year of change. That is, in our analysis, Joinpoint regression analysis was analyzed with the default settings, which have limitations such as a maximum of two joinpoints in the research period and a minimum of two observation points between the joinpoints [17]. Furthermore, the study analyzed annual suicide rates, and data during the pandemic period are only available for three years, from 2020 to 2022. And thus, because there were not enough data points to analyze changes in suicide rates between, before, and after the onset of the pandemic, joinpoint analysis, although a widely used statistical analysis method to analyze changes in time-series trends, may not have adequately captured short-term changes in suicide rate trends in this study.
Rurality and suicide
Previous studies indicated that rural rates of suicidal behavior and death by suicide were often higher than those in urban areas [18], but some studies have reported that the association between suicide risk and rurality/urbanicity varies significantly by gender and age [19–21]. The results of this study showed that in Japan from 2009 to 2020, suicide rates tended to be higher in rural areas than in urban areas for men, but there was little difference between rural and urban areas for women. There have been four reports on differences in the distribution of suicide rates between rural and urban areas during the pandemic, but these results are not consistent [22–25]. The greatest falls in suicide rates in the USA during 2020 occurred in large metropolitan urban centres, whereas rates did not fall in the nation's predominantly rural regions [22]. Higher population density predicted suicide rate increases across Mexico’s 32 states in 2020, with approximately twice as many suicides occurring in Mexico City than the expected value [23]. The national suicide rate in Brazil fell by 13% between March and December 2020, but substantial excess suicide risks were observed in some gender and age groups in states with greater population density [24]. In Ecuador, the rate of suicides occurring in urban and coastal areas increased [25]. The results of this study show that suicide rates at three different levels of rurality for both men and women remained roughly parallel before and after the onset of the pandemic, which suggests that differences in prefectural rurality levels do not seem to contribute much to the increase in suicide rates during the pandemic. However, on closer inspection, it is possible that, for both men and women, there is a slightly stronger tendency for suicide rates to increase during the pandemic period in prefectures with lower levels of rurality than in those with higher levels. This may indicate that the impact of the pandemic on suicide risk has been slightly stronger in prefectures with lower levels of rurality in Japan. Differences between urban and rural areas, the risk of COVID-19 infection and restrictions on daily life, may have influenced the differences in changes in suicide rates.
Deprivation and suicide
Previous articles have found relatively strong evidence for positive associations between area-level socioeconomic deprivation and suicidal behavior among men but weaker evidence for women [11, 26]. A study using data on suicides in Japanese municipalities between 2009 and 2017 found an association between social deprivation and suicide risk, but it was more pronounced among men [27]. The results of this study showed that in Japan from 2009 to 2020, suicide rates tended to be higher in socioeconomically more deprived areas than in less deprived areas for men, but there was little difference between more deprived and less deprived areas for women. A finding that the COVID-19 pandemic has shown a disproportionate socioeconomic impact on suicide rates have so far come from India [28]. The research examining trends in suicide rates in India across regions with different socioeconomic status found that the increase was fivefold higher among males residing in states with high deprivation. A review article of research up to July 2022 indicated that evidence from some countries and regions partially supported the potential role of socioeconomic disadvantage as an important actionable effect modifier of the association between pandemic-related stressors and suicide [4]. The results of this study show that suicide rates at three different levels of deprivation for both men and women remained roughly parallel before and after the onset of the pandemic, which suggests that differences in prefectural deprivation levels do not seem to contribute much to the increase in suicide rates during the pandemic. However, on closer inspection, it is possible that, only for men, there is a slightly stronger tendency for suicide rates to increase during the pandemic period in prefectures with higher levels of deprivation than in those with lower levels. This may indicate that the impact of the pandemic on suicide risk has been slightly stronger in more socioeconomically deprived prefectures among Japanese men. The association between suicide and area deprivation during the pandemic in Japan will need to be studied further.
Suicides by age
The results of this study also showed that during the research period there were differences in suicide rates by age, especially after about 2019, with distinct differences between those under 60 and over 60 years of age. That is, a trend in the suicide rates was changing for both the under 60 and 60 or over age groups around 2019, but the change appeared to be much smaller for the 60 or over age group. The previously mentioned review article indicated that differences in risk of COVID-19 infection might have an effect on the distribution of area suicide risk [4]. That is because, in some countries and regions, suicide rates among older people, especially older men, increased disproportionately during the pandemic, possibly due to increased fear of infection and death, loss of partners and close friends, and loneliness due to isolation; stressors that affect older adults more than their working-age counterparts. However, this study showed that while the pandemic may have altered suicide rates among the elderly in Japan, this effect was considerably smaller than among younger generations. Therefore, the impact of differences in risk of COVID-19 infection on people's suicide risk in Japan would not be as substantial.
The results of this study showed that suicide rates increased during the pandemic among men aged 40 to 59 years. This is something that was not emphasized much in a previous report in Japan [9]. This group had an increased suicide rate in 2022 (30.6 per 100,000) compared to 2021 (28.1 per 100,000). Previous reports from Japan have been up to 2021, and thus they would have not detected an increase in this gender-age group. Men of middle-aged are considered a group at comparatively high risk of suicide in times of economic recession in previous studies [29]. The result of this study may be an indication that the pandemic has lasted long enough, and the socioeconomic situation has deteriorated, gradually taking its toll on this gender-age-group in Japan.
Limitations
The study had several limitations that deserve discussion. First, analyses are based on data from suicide statistics compiled by the police agency based on data on unnatural deaths, which might underestimate true suicide rates. However, the focus of this study is not on the extent of suicide rates, but rather on the time trends in suicide rates. As there has been no change in the way data are collected by the police over the period of this study, we believe that if there has been an underestimation of the number of suicides, the impact may not be substantial. Second, this study used prefectures as the geographical unit, which is a comparatively large unit. And thus, deprivation assessed by average income and rurality assessed by population density may not adequately reflect the situation of many of the residents. Consequently, it will be necessary in the future to conduct analyses on a smaller area unit or using data from individuals. Third, since the study was stratified by gender and age group, some categories may not have had sufficient power to detect statistically significant changes, even if the APC values were of some magnitude. Last, the study was descriptive in design, and the delineation of the complex relationships among risk factors of suicide was beyond the scope of this study.
Implications for public health policies and future research
The findings of this study showed that the decreasing trend in suicide rates in Japan before the onset of the COVID-19 pandemic was followed by a substantial change in the trend after the onset of the pandemic. This may indicate that support for the needy has not been successful in Japan because adequate employment support and aggressive fiscal spending may prevent an increase in suicides during economic downturns [30]. And thus, future research will be needed to investigate the impact of financial and employment support initiatives on people's mental health and suicide risk in Japan during or after the pandemic. In addition, as of September 2023, Japan continues to see new cases of COVID-19 infections, but few restrictions to daily life have been put in place as a measure to combat infection. However, the number of suicides in Japan will need to be monitored carefully in the future, as there may be ongoing adverse impacts on socio-economically vulnerable populations, even today.