Article Text

Demographic and epidemiological decomposition analysis of global changes in suicide rates and numbers over the period 1990–2019
Free
  1. Paul Siu Fai Yip1,
  2. Yan Zheng2,
  3. Clifford Wong3
  1. 1 HKJC Centre for Suicide Research and Prevention, The University of Hong Kong, Hong Kong, People's Republic of China
  2. 2 The School of Nursing, The Hong Kong Polytechnic University, Kowloon, People's Republic of China
  3. 3 Social Work and Social Administration, The University of Hong Kong, Hong Kong, People's Republic of China
  1. Correspondence to Dr Paul Siu Fai Yip, HKJC Centre for Suicide Research and Prevention, The University of Hong Kong, Hong Kong, People's Republic of China; sfpyip{at}hku.hk

Abstract

Background Suicide presents an ongoing public health challenge internationally. Nearly 800 000 people around the world lose their life to suicide every year, and many more attempt suicide.

Methods A decomposition analysis was performed using global suicide mortality and population data from the Global Burden of Disease Study 2019.

Results Despite a significant decrease in age-specific suicide rate between 1990 and 2019 (-4.01; from 13.8% to 9.8% per 100 000), the overall numbers of suicide deaths increased by 19 897 (from 738 799 to 758 696) in the same time period. The reductions in age-specific suicide rates (−6.09; 152%) contributed to the overall reductions in suicide rates; however, this was offset by overtime changes in population age structure (2.08; −52%). The increase in suicide numbers was partly attributable to population growth (300 942; 1512.5%) and population age structure (189 512; 952.4%), which was attenuated by the significant reduction in overall suicide rates (−470 556; 2364.9%). The combined effect of these factors varied across the World Bank income level regions. For example, in the upper-middle-income level region, the effect of the reduction in age-specific suicide rates (−289 731; −1456.1%) exceeded the effect of population age structure (124 577; 626.1%) and population growth (83 855; 421.4%), resulting in its substantial decline in total suicide deaths (−81 298; −408.6%). However, in lower-middle income region, there was a notable increase in suicide death (72 550; 364.6%), which was related to the net gain of the reduction in age-specific suicide rates (-115 577; -580.9%) and negated by the increase in the number of suicide deaths due to population growth (152 093; 764.4%) and population age structure (36 034; 181.1%).

Conclusion More support and resources should be deployed for suicide prevention to the low-income and middle-income regions in order to achieve the reduction goal. Moreover, suicide prevention among older adults is increasingly critical given the world’s rapidly ageing populations in all income level regions.

  • public health
  • suicide/self-harm
  • epidemiology
  • policy analysis

Data availability statement

Data are available in a public, open-access repository. The data in the study are open to the public.

Statistics from Altmetric.com

Introduction

Suicide presents an ongoing global public health challenge, with nearly 800 000 deaths every year.1 2 Despite this, suicide has not received the attention given to other global public health challenges, compared with communicable diseases such as HIV/AIDS and non-communicable causes such as cancer. The WHO Mental Health Action Plan highlights the urgency of suicide prevention and proposes a global target of 10% reduction in suicide rate between 2012 and 2020.3 To achieve this, the WHO suggested that member states should develop and implement comprehensive national strategies, which particularly focused on groups with increased risk of suicide.3 Moreover, suicide rate remains a key indicator for Target 3.4 of the Sustainable Development Goals, which addresses all major health priorities and calls for reducing non-communicable diseases and other health hazards.4

Around the world, suicide and suicidal behaviour vary by age groups, genders and geographical regions.5 While suicide can occur throughout the lifespan, in almost all regions of the world, suicide rates are highest among people aged 70 years or above. For those aged 15–29 years, suicide is the second leading cause of death.1 Besides, it is of particular concern that 77% of global suicides occur in low-income and middle-income countries,6 where mental health resources and services are usually insufficient for comprehensive early identification, treatment and support of people in need. Moreover, in these countries, the male-to-female suicide ratio is much lower than that in wealthier countries.2

Overtime changes in suicide rates and number of suicide deaths are related to changing epidemiological (eg, age-specific suicide rates) and demographic (eg, population growth and population age structure) factors. Epidemiological factors relate to issues such as age and gender, while demographic factors relate to population growth and population age structure. Demographic components are closely associated with the increasing prevalence of non-communicable diseases such as cardiovascular disease, cancer and diabetes.7–9 This may also well explain why the global number of suicide death continues to rise, despite an overall global decrease in suicide rates. However, the effect of demographic factors on global trends in suicide death is not well understood, which may explain difficulties in setting realistic and achievable targets for suicide prevention.

Since 1990, the whole world has been experiencing a rapid demographic transition, and the total number of suicide deaths has generally been rising, despite the significant reduction in global age-standardised mortality rates from suicide.10 Our study aimed to examine the contributions of epidemiological and demographic factors to the total number of suicide deaths over the last 30 years (1990–2019). A clear description of the complex relationships between population growth, population age structure, income level, gender and age-specific suicide rates may provide a better understanding of the global overtime changes in suicide rates and number of suicide deaths. This information could underpin the development of more focused and potentially more cost-effective suicide prevention strategies.

Data and methods

Data were obtained from the Global Burden of Disease Study (GBD) 2019.11 This dataset provides an estimation of population for each of 204 countries and territories and the globe and also captures the information for a total of 369 diseases and injuries from 1990 to 2019 by age and gender. The GBD dataset also provides population estimates for 1950–2019 by location, different age groups and gender, with data sources coming from 1250 censuses and 747 population registry location-years. It enables comparisons over time, across populations and between age groups.

Our study examined changes in the suicide rates and number of suicide deaths between 1990 and 2019 by gender and age groups in the four World Bank income level regions. This reflects 201 countries, territories and subnational locations categorised into low-income, lower-middle-income, upper-middle-income and high-income regions. The percentages of the world’s population living in these income level regions were 9%, 41%, 34% and 16%, respectively, which was calculated based on GBD population data. The list of countries in each income level region is provided in online supplemental appendix 1. The International Classification of Diseases (ICD) definition of suicide mortality as death caused by self-harm (E950–E959 for ICD-9; X60–X64.9, X66–X84.9 and Y87.0 for ICD-10) was used. In this study, suicide deaths and population data were categorised as under 25 years, 25–44 years, 45–64 years and 65+ years.

Decomposition analyses were used to identify the impacts of changes in age-specific suicide rates, population growth and changing population age structure on the suicide rates and the number of suicide deaths. The formulae for the two-factor and three-factor decomposition could be found in online supplemental appendix 2. Changes in suicide rates between 1990 and 2019 were decomposed into the changing age-specific, gender-specific suicide rates and population age structure. Decomposition of the number of suicide deaths for the four income level regions examines the influence of three components: changing age-specific, gender-specific suicide rates; population age structure; and population growth. The net changes in these three components were equal to the observed change in the total number of suicide deaths.

Results

Suicide rates by age and gender across the four income regions

Figure 1 reports overtime trends in suicide rates across the four income level regions. In 1990, the overall suicide rate was 13.8 per 100 000, and it decreased to 9.8 per 100 000 in 2019. Over this time period, for men, the overall suicide rate decreased from 16.6 per 100 000 to 13.5 per 100 000, and for women, it decreased from 11.0 per 100 000 to 6.1 per 100 000. Generally, suicide rates reduced over time in all four income regions, with the upper-middle-income region experiencing the most significant decline (−6.25 per 100 000), followed by the lower-middle-income region (−2.51 per 100 000), the low-income region (−1.96 per 100 000) and the high-income region (−1.77 per 100 000). Overall, the decline in suicide rates for women was greater than that for men (−4.91 vs −3.09 per 100 000), especially in the upper-middle-income region (−8.12 vs −4.37 per 100 000).

Figure 1

Trends in suicide rates for men and women across four income level regions, 1990–2019.

Table 1 reports the decomposition findings that explain the overtime declines in the suicide rates across the four income level regions. The overall reduction (−4.01 per 100 000) was mainly due to the reduction in age-specific suicide rates (−6.09; 152%), although this effect was partly offset by the impact of the changing population age structure (2.08; −52%). The reduction in age-specific suicide rates was the major driver for the declining rates of suicide, offsetting the effect of the changing population age structure. For example, in the high-income level region, the reducing age-specific suicide rate (−3.83; 216.3%) had a much larger impact than the change in population age structure (2.06; −116.3%).

Table 1

Contributions of population age structure and age-specific suicide rates to the changes in suicide rates across the four income level regions, 1990–2019

Suicide deaths by age and gender across the four income level regions

Figure 2 shows the changing trends in the number of suicide deaths over time across the four income level regions for both genders. The overall number of deaths from suicide increased by 19 897 (from 738 799 to 7 58 696) between 1990 and 2019. Specifically, in lower-middle-income region, the number of suicide deaths increased by 72 550 (from 232 340 to 304 890), which is much larger than the increases in low-income (18 549) and high-income (10 097) regions. The increases in these three regions were offset by the significant decrease in the number of suicide deaths (−81 298) in the upper-middle-income region (from 322 130 to 240 832), resulting in the global net increase of 19 897.

Figure 2

Trends in the number of suicide deaths for men and women across four income level regions, 1990–2019.

Table 2 reports the decomposition analysis of the overtime changes in the number of suicide deaths between 1990 and 2019. The main contributor to the overall increase in the total number of suicide deaths (19 897) was population growth (300 942; 1512.5%), followed by population age structure (189 512; 952.4%). However, these impacts were greatly offset by the effect of the substantial reduction in the age-specific suicide rates (−470 556; −2364.9%). More specifically, in the upper-middle-income region, the contribution of reductions in age-specific suicide rates (−289 731; −1456.1%) largely overshadowed the effect of population age structure (124 577; 626.1%) and population growth (83 855; 421.4%), resulting in the substantial decline in total suicide deaths (−81 298; −408.6%). However, in lower-middle-income level region, the declining age-specific suicide rates (−115 577; −580.9%) only partly negated the increase in the number of suicide deaths due to population growth (152 093; 764.4%) and population age structure (36 034; 181.1%). In low-income and high-income level regions, although the age-specific suicide rates made less notable contributions, owing to a much lower degree of the changes in population growth and population age structure, the increase in the number of suicide deaths was comparatively smaller.

Table 2

Contributions of changes in the number of suicide deaths by population growth, population age structure and age-specific suicide rates across the four income level regions, 1990–2019

The overall contribution of population age structure mainly came from the 45–64 (565.2%) and 65+ (528.7%) age groups. This effect was observed in middle-income as well as high-income level regions, reflecting the global effect of population ageing. Generally, between 1990 and 2019, no major gender differences were observed in the decreasing suicide rates (men: –220 368 (–1107.5%) and women: −250 189 (−1257.4%)). However, unlike women, there was a marked increase in the total number of male suicide deaths, which was mainly explained by the significant effect of male population growth (177 128; 890.2%) and male population age structure (120 186; 604.0%) (corresponding female figures: 123 814, 622.3%, and 69 325, 348.4%, respectively). Contribution patterns of men and women varied across regions. This was particularly notable in upper-middle-income regions where men contributed much less than women to the reduction in the number of suicide deaths (men: −12 097 (−60.8%) and women: −69 202 (−347.8%), respectively).

Discussion and conclusion

This study identifies important underlying drivers for the changing trends in both suicide rates and the number of suicide deaths across different income level regions over the past 30 years. Between 1990 and 2019, despite the declining age-specific suicide rates, the resulting reduction of suicide rate was offset by the population ageing. Also, the overall number of suicide deaths has been increasing due to the effects of population growth and population age structure despite the significant improvement of suicide rates, especially in lower-middle-income and upper-middle-income regions. The combined impacts of epidemiological change and demographic components underpin the different suicide patterns across income level regions and gender.

It was encouraging to find the overall reductions in suicide rates in all income level regions and for both genders over the study period, despite the notable regional-specific and gender-specific differences.1 2 The reasons for the significant decline in suicides across all income level regions have yet to be determined. Some impacts would have come from the coordinated and comprehensive global endeavours by the WHO2 3 and the United Nations,12 which provided effective support and guidance for the implementation of national suicide prevention initiatives. Moreover, some suicide prevention strategies, for example, optimising suicide prevention programmes in Europe,13 government-led comprehensive suicide prevention programmes in Organisation for Economic Co-operation and Development (OECD) nations14 and restriction of means in Hong Kong and Taiwan,15 16 provide empirical evidence and good practice benchmarks for effective suicide prevention and intervention. Therefore, it is important to develop cost-effective global and national preventive measures for maintaining the decreasing trend in suicide rates.

Our results show that the increase in the global number of suicide deaths was primarily due to population growth, particularly in lower-middle-income region, which greatly offset the effect of the declining age-specific suicide rates. In low-income region, the contribution of population growth should also be of substantial concern in view of the global population projection. Between 2019 and 2050, sub-Saharan Africa and Central and Southern Asia could expect to account for over 75% of the additional 2 billion total global population growth.17 Therefore, the effect of population growth might be even larger in low-income and middle-income countries in the coming decades.

Population ageing, as a global demographic ‘megatrends’,17 also played an important role in affecting the change in the total suicide deaths. Increasing life expectancy and declining fertility continue to affect global age structure.18 Populations around the world are experiencing19 and will continue to experience pronounced and historically unprecedented ageing in the coming decades.20 Population ageing is a crucial concern in all developed countries,21 which could be attributable to the boom/bust cycles in fertility.22 However, in the coming decades (between 2019 and 2050), the least developed countries are also projected to experience the fastest increase of the older people in their populations.23 As suicide rates are highest among the elderly (70 years or above) for both genders in almost all regions of the world,2 the rapidly ageing population globally will pose huge challenges for the reduction in the number of suicide deaths in the future. The improvement of female suicides especially in low-income and middle-income countries would continue to contribute significantly to the reduction of suicide rate and numbers in the future. Resources should thus be deployed to prepare for the burden of population growth and changing population age structure, particularly for less-well-developed countries and the well-being of women in low-income and middle-income countries.

There are limitations to this study. First, our study mainly focused on the demographic drivers of the changes in suicide rates and the number of suicide deaths in different income level regions. Many factors, for example, suffering from psychiatric disorders, low income, drug abuse and unemployment24 or suicide method availability and lethality and media reporting,15 25 might also affect suicide rates, thus playing important roles in suicide changes in different income level regions. Therefore, further studies could investigate the influence of these factors, which might explain regional differences in suicide rates and suicide deaths. Furthermore, this study categorised the older population as those aged 65 years and older; however, previous research has shown that gender difference in suicide rates becomes especially important among 80-year-old population, where suicide rates are five times higher for men than for women.26 Future study should pay more attention to suicide and its causes among very old people.

The decomposition analyses in our study highlighted the importance of including demographic drivers such as population growth and population age structure in examining the changing trends over time in suicide rates and the number of suicide deaths. It shows that the improvement in suicide rate in high-income level region has limited the impact on the overall global burden of suicide. The lower-middle-income and upper-middle-income countries are crucial in suicide prevention efforts, and they will determine whether global suicide reduction targets can be attained. This study highlighted the considerable imbalance of the resources in carrying out suicide prevention work especially in low-income and middle-income countries. It is a time to revisit this situation to ensure that sufficient resources can be redeployed globally to meet the future challenges.

What is already known on the subject

  • Suicide presents an ongoing global public health challenge, with nearly 800 000 deaths every year.

  • Changing suicide rates and the number of suicide deaths are believed to result from the changing epidemiological (eg, age-specific suicide rates) and demographic (eg, population growth and population age structure) factors.

What this study adds

  • The reduction of suicide rate in the last three decades is largely contributed by the lower-middle-income and upper-middle-income countries.

  • A rapidly ageing population across the four World Bank income level regions will inevitably pose challenges for the reduction in the overall number of suicide deaths.

  • More resources should be deployed to low-income and middle-income regions for suicide prevention.

Data availability statement

Data are available in a public, open-access repository. The data in the study are open to the public.

Ethics statements

Patient consent for publication

References

Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

Footnotes

  • Contributors PSFY has contributed to the conceptualisation, analysis and writing of the paper. YZ has contributed to the analysis and writing of the paper. CW has contributed to the analysis of the paper.

  • Funding This study was funded by Humanities and Social Sciences Prestigious Fellowship (for Yip).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.