Introduction

The proportion of the population over 60 years old is up to 18.7% according to the 7th National Census of China (2020) [1], which means that China has entered a deep aging society. In 2021, the National Bureau of Statistics of China reported that the total number of deaths in the country reached nearly 10.14 million, of which more than 2/3 of the population is over 60 years old [2]. The top three causes of death in China are chronic diseases, injuries, as well as infectious diseases, maternal and infant diseases, and nutritional deficiencies, with injury-related deaths ranking second among the elderly [3]. In addition to death, disability, and personal and family suffering, the consequences of injury will also cause a serious burden of medical care [4]. In this regard, the Chinese Communist Party and government are highly concerned about the death of elderly injuries and have introduced relevant strategies and measures. However, research on injury death of the elderly is still mostly limited to a certain province, prefecture, and city, and there is no comprehensive analysis of the situation In this systematic review, we use big data to conduct a meta-analysis on the types of injury deaths, the characteristics of "population, places, and times" and dynamic changes in the elderly population in China in the past 20 years (2000–2020), and the results can provide a basis for formulating corresponding prevention and control measures, thereby preventing and reducing the occurrence of injuries and deaths.

Material and methods

The systematic review was registered in PROSPERO under protocol number CRD42022359992.

Inclusion and exclusion criteria

Inclusion criteria: (1) Resident senior citizens aged 60 years in China from 2000 to 2020; (2) Injury death as the research outcome goal; (3) Cause of death classified according to ICD-10 code; (4) Provide injury mortality or the number of deaths, sample size, or the required value can be calculated based on the data given in the literature; (5) Source of data from the local death cause monitoring system or authoritative system; (6) Cross-sectional study.

Outcomes

Injury mortality among the elderly

Exclusion criteria: (1) Documents with ambiguous, incomplete, or unconverted data; (2) The quality of the literature is too low (AHRQ score below 3); (3) Repeated publications.

Search strategy

This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was searched through seven electronic databases without language restriction: Chinese National Knowledge Infrastructure (CNKI), Chongqing VIP Database, WanFang Database, MEDLINE, Embase, SinoMed and Web of Science. To collect epidemiological cross-sectional research papers on injury and death of Chinese people aged ≥ 60 years published in China and abroad, and the search time limit was from January 2000 to December 2020 (including references to the literature to supplement relevant studies). The retrieval takes the combination of subject headings and free words. Chinese search terms include: “中国”, “中国人”, “我国”, “老年人”, “老人”, “老年”, “伤害死亡”, “伤害”, “死因”, “死亡率”, “粗死亡率”, “标化死亡率”, “死因监测”; English search terms include China, Chinese, elderly, elderly people, aged, injury death, injury, death, mortality rate, crude mortality rate, standardized mortality rate, mortality surveillance.

Literature screening and data extraction

All publications that were identified from literature searches were initially extracted by two independent reviewers. Data were stored in a standardized tabular format and the full list was assessed for eligibility by two different reviewers independently. Following the screening, any discrepancies were discussed between the reviewers. Any further conflicts were resolved by reviewing the original publication and additional adjudication. Information from selected literature was extracted as followed: (1) The first author, the area, and time of the investigation; (2) Outcome indicators (injury mortality) and outcome measurement data (sample size, age and gender of patients, place of residence, investigation time and injury type); (3) Key elements of risk assessment for bias.

Quality assessment

Evaluation tools recommended by Agency for Healthcare Research and Quality (AHRQ) tool(www.ahrq.gov) were used to assess the quality of all cross-sectional studies. AHRQ was an 11-item instrument with 3 options: the ‘Yes’ would be scored as ‘1’, ‘No’ or ‘Unclear’ would be scored as ‘0’. The articles were scored as follows: 0–3 = low quality; 4–7 = moderate quality; 8–11 = high quality. The quality of the literature was evaluated by two independent reviewers (Y.SL and T.JX), and a third party was consulted in case of disagreement.

Statistical analysis

All results for the prevalence of injury mortality among 187 488 elderly Chinese were visualized using forest plots. The heterogeneity between the involved studies was assessed using the I2 statistic and Q tests. The fixed effects model was used when the heterogeneity test results were considered to be good(P > 0.1 and I2 < 50%); conversely, the random effects model was utilized when I2 ≥ 50%. Subgroup analysis was carried out according to the characteristics of the population, such as gender, age, region, urban and rural distribution, statistical year, and injury type; sensitivity analysis was carried out by one-by-one elimination method, and Publication bias was assessed using Egger's test and a funnel plot of linear regression of the log ORs on the inverse root of the sample size, and P < 0.05 was considered statistically significant difference. Statistical analysis was performed with the software R (R Project for Statistical Computing, version 4.1.2, http://www.r-project.org/).

Results

Literature screening process and results

A total of 1864 related pieces of literature were originally identified, and after the layer-by-layer screening, 41 pieces of literature were ultimately incorporated, with a total of 187 488 elderly people who died of injury, comprising a sample population of 124 798 756. The literature screening process and results are shown in Fig. 1.

Fig. 1
figure 1

Flow diagram for systematic review and meta-analysis. Flowchart demonstrating selection of eligible studies. The databases retrieved and the number of the literature identified are as follows: CNKI (N = 91), VIP (N = 63), WanFang Data (N = 389), MEDLINE (N = 193), SinoMed (N = 13), Embase (N = 3), and Web of Science (N = 1112)

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Basic characteristics and risk of bias assessment of the included literature

The basic characteristics and risk of bias evaluation of the incorporated literature are demonstrated in Table 1.

Table 1 Main information and risk of bias assessment of the included literature
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Results of the meta-analysis

Literature basic situation and quality

This review collected 41 pieces of literature, and the average AHRQ score was 6.85, demonstrating that the quality of the literature was optimal. The sample involved 124 798 756 elderly people, with 187 488 injury death, in which males (85 119) were slightly more than females (82 300). According to the results of the heterogeneity test (P < 0.001, I2 = 100%), a single-sample rate meta-analysis was performed using a random-effects model, and the results of the forest plot are demonstrated in Fig. 2.

Fig. 2
figure 2

Forest plot of injury mortality point values and interval estimates

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Total injury mortality

The results of the random effects model showed that the total injury mortality of the elderly in China was 135.58/105 [95%CI: (113.36 to 162.14)/105].

Subgroup analysis Results (1/10.5 )

The subgroups analyzed the injury mortality rate of different factors such as gender, age, region and time. Due to the large heterogeneity among subgroups, random model analysis was still used. The results showed that the mortality rate of males was higher than that of females (146.00 vs. 127.90, P < 0.05); the author divided the age into six groups, and the mortality rate increased sharply with age, especially in the group over 80 years old (60-year-old: 72.01 < 65-year-old: 91.83 < 70-year-old: 130.05 < 75-year-old: 203.25 < 80-year-old: 384.88 < 85-year-old: 854.42, P for trend < 0.05), see Fig. 3 and Table 2; according to the spatial analysis, the mortality rate in China was as follows: middle: 215.26 > western: 143.84 > east: 130.73, rural (170.35) is higher than urban (131.99); in terms of time, the injury mortality rate was calculated based on the per capita GDP level for 20 years (across four five-year plans), In the first two five-year plans, the overall change demonstrated the same trend as the per capita GDP level, although in the latter two, the trend was the opposite (Fig. 4). According to 41 included literatures, more than 12 types of injuries were involved, and the top three were falling (43.91), traffic accidents (24.49), and suicide (15.88), see in Table 3; and the composition of different causes of death from injuries among the elderly in China from 2000 to 2020 (%) is shown in Fig. 5.

Fig. 3
figure 3

Changes in injury mortality rates among the elderly of different age groups in China, 2000–2020

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Table 2 Random effects model subgroup analysis and comparison
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Fig. 4
figure 4

Columnar diagram of GDP level and elderly injury mortality during the four five-year plans

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Table 3 Combined rates of injury deaths by region, gender, and type of injury in China in this study
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Fig. 5
figure 5

Composition of different injury causes of death among Chinese elderly from 2000 to 2020 (%)

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According to the statistics from 41 literatures, there are more than 12 causes of injury and death in China. They are falling, traffic accidents, suicide, drowning, poisoning, fire, homicide, transportation accidents, electric shock, crushing, accidents caused by the natural environment, suffocation, etc. The first six types accounted for 85.55% of the total causes of death. Falling is the main cause of death (41.36%), followed by traffic and suicide. The death rate of the first two injury types was higher in eastern than in western, and the fall death rate for males was slightly lower than that of females, but the suicide death rate was slightly higher than that of females, and the traffic death rate was 1.79 times higher than that of females.

Sensitivity analysis

The sensitivity analysis was carried out by the one-by-one elimination method, and the results were between 132.40/105 and 143.37/105, which was not much different from the total injury mortality rate, indicating that the results of this study were stable, as shown in Fig. 6.

Fig. 6
figure 6

Forest map after culling one by one

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Evaluation of publication bias

The funnel plot of total injury mortality was not significantly asymmetric. Combined with the results of Egger's plot (t = -1.58, P = 0.122), it suggested that there was a small possibility of publication bias, see Fig. 7.

Fig. 7
figure 7

Funnel plot of total injury mortality rate

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Discussion

The above results show that the injury mortality rate of the elderly in China after entering the aging period is higher than that before and has broken the original stable situation [46]; it is higher than that of the United States and Brazil in 2000 and is at a medium–high level compared with the EU countries in the early twenty-first century [47,48,49]. Mortality levels indicate that injury mortality in the elderly population varies by country and time. Of course, to more accurately compare this rate with countries, a standardized rate is ideal.

Another prominent feature of injury death in China is that there is a gender difference between males and females, which is consistent with the results of most countries. The mortality rate of different age groups varies significantly. Injuries increase exponentially with age and the rate of falling increases with age. The reason may be the negative impact of aging on the elderly [50], and it is particularly important to prevent falling. The world has become intelligent, and the elderly are not as receptive to intelligent technology as the young and middle-aged. For example, in bad weather, a young man can use his smartphone to solve his lunch while sitting in an office, while an old man needs to go to the street to buy food. It is entirely possible to suffer injury.

2000–2020 was the period from the implementation to the completion of China's four "five-year plans", during which China completed the rapid change from reform to opening up, and the Chinese economy, social environment, family living patterns, and even development policies changed dramatically. This has resulted in large differences in economic development and GDP levels between central, eastern, and western China, which inevitably affect the overall changes in injury mortality among older adults in China. In the first decade, the flow of economic growth led to frequent population movements and traffic, and these phenomena inevitably resulted in a relative increase in traffic accidents and other accidental injuries [51]. GDP growth is largely dependent on industrial production and rising labour levels, which have resulted in increased stress in work and life; these physical to psychological stresses have been reported in other studies in China, so their effects on accidental injuries cannot be ruled out either. GDP growth has a positive impact on increasing the country's economic power, improving people's living standards, and promoting social progress. Meanwhile, from a management and public health perspective, it may play a significant role in reducing the occurrence and prognosis of injuries if the positive effects of GDP are adequately considered.

In the early stage of China’s reform and opening up, the “Seventh Five-Year Plan” divided the entire region into eastern, central, and western regions according to the high, intermediate, and low levels of economic and technological development [52]. The injury mortality in the central region is the highest, which can be explained from the following three aspects. First, compared with the eastern and coastal regions, central China has a cold climate, relatively scarce resources, and relatively lagging economic level [53, 54]. Moreover, diet type and structure, lifestyle, and habits differ among the regions (such as Inner Mongolia, Heilongjiang, Jilin Province, etc.), and the increased risk of death from accidental injuries cannot be excluded as a long-term effect of these factors. Second, the social security development system and speed in the central region are relatively lagging, and the medical and healthcare technology and facilities for elderly special groups are not as ideal as those of the eastern or coastal regions [55]. Lastly, the density of transportation arteries in central China (such as Jiangxi, Hubei, Hunan Province, etc.) is relatively high [56], and many transportation lines are designed to pass through dense areas of urban dwellers due to the regional culture and lifestyle mindset, which to a certain extent are more prone to traffic accidents. While the injury mortality in the eastern region is slightly higher than that in the western region. It is believed that this phenomenon does not rule out the double-edged sword effect of factors such as the aging degree, the higher GDP level, and the more congruent health care system in the eastern region.

After the urbanization development was included in the special key plan in China's "Tenth Five-Year Plan", the level of urbanization has climbed sharply over the past 20 years, from 36% in 2000 to 63.89% in 2020 [2]. This trend has brought about major changes in the rural population, labor force size, and structure –– the average age of agricultural laborers is 48.45 years old, and as many as 75.24% are female. The influx of rural youth and middle-aged labor into cities has considerably accelerated the aging and feminization of the rural population [57], which is also one of the factors that cause rural injuries to be higher than urban ones.

Another feature is that injury mortality in China has raised firstly and then reduced over the past 20 years (2000–2020). Since entering an aging society in 2000, the injury mortality rate has remained high for ten years. With the emergence and popularization of the concept of population aging, the national injury prevention, and control work has been carried out in an all-round way [58], and the Chinese Party and government have issued the "Quality Development Outline (2011–2020)", "National Disability Prevention Action Plan (2016–2020)", "Healthy China 2030 Planning Outline" and a series of strategies or measures such as injury prevention and control, such as road safety-related policies, although the activities of injury prevention, obstacle reduction, and aging-appropriate renovation have been carried out at different levels in China, and achieved certain results, the degree of aging in China Unabated, resulting in a continued increase in injury mortality.

The composition of the cause of injury death still displayed certain characteristics. In terms of period, the top six causes of death in China, including falling, traffic accidents, and suicide, cover 84.1% of the total injury causes, which is substantially higher than that in the EU (64.1%). Among these causes of death, falling is the earliest cause of injury death. Among Chinese people aged 65, an average of 3–4 people in every 10 have fallen. According to this estimate, about 57.192 million to 76.256 million people will fall every year at this stage, and this phenomenon will increase with the acceleration of the aging degree. 40% to 70% of people who fall will suffer from various degrees of injury and receive medical treatment. It is worth mentioning that about 22.34% of those who fall have suffered serious injury or even paralysis [59].

In contemporary China, traffic accidents have virtually become a social problem. Since the beginning of the twenty-first century, the mileage of highways and the number of motor vehicles have raised markedly and have been extensively managed. Road traffic injuries are extremely common, among which injuries involving "people" account for 78.3% ~ 96.5% of all causes, and illegal acts such as speeding are very common [60]. At the same time, frequent and dense population flow leads to traffic jams and traffic accidents.

Compared with the BRICS countries (China, Russia, Brazil, India, and South Africa), the suicide mortality rate among those aged 70 years is the highest in China, and the phenomenon of suicide is severe (2015) [61]. The main reasons for this phenomenon are: first, illness and persistent economic burden. The prevalence of chronic diseases among the elderly in China is 86.23%, of which 76.30% suffer from various chronic diseases at this stage [62, 63]; the second is lack of emotion and loneliness. If it cannot be ruled out that China's "family planning" policy, which was set as a basic national policy in 1982, has led to the emergence of a large number of "4 + 2 + 1 Family", "8 + 2 + 1 Family" and " The Loss of Only Child Family", factors such as widowhood can affect emotions [64].

Because of the current situation of injury and death among the elderly in China, during the "14th Five-Year Plan" period, a list of rectifications such as suitable aging and a barrier-free environment has been issued. However, to achieve Healthy Aging, multiple aspects need to be integrated, such as industrial structure adjustment, improving the elderly's Self-health quality, creating a humanistic environment of government-community-family integration, and reducing the risk of injury and death.

This study has certain limitations. First, the heterogeneity of the included studies is high due to the characteristics of a single rate meta-analysis; second, in the hierarchical analysis, the literature data from different regions are not uniform, and it is also difficult to obtain data standardization background information; third, the analysis of the influencing factors of accidental death is limited to a certain extent, and there is no data on living habits, psychological factors, and post-injury nursing behaviors.

This systematic review objectively reflects the current status of injury deaths and causes of death among the elderly in China. The data is derived from the public security bureaus, death-cause monitoring sites, and CDCs of various provinces and cities in China, which are authentic and authoritative. Sensitivity analysis showed that the results of the meta-analysis of this study were stable, and the publication bias assessment also showed that there was no obvious publication bias, so the results obtained were more representative and reliable than a single study. The results of this study provide an important foundation for future prospective research and the initiation of advanced injury prevention plans in China. Governments and local institutions should consider implementing public health measures to prevent injury death. Examples include reducing income inequality, allocating more resources to vulnerable groups, and implementing targeted group prevention [65].