Introduction

Spinal injuries are life-disrupting events that lead to varying degrees of motor, sensory, and autonomic deficits and often result in severe post-traumatic complications. These injuries cause substantial burdens for patients, their families, and society.[1] There is no definitive therapy; therefore, prevention is emphasized. A thorough epidemiological understanding is vital for implementing preventive measures and planning clinical services.

In recent decades, epidemiological studies have been published, and researchers have learned much about the characteristics of spinal injuries. Most studies have come out from Europe, North America, and Australia.[2] In the 1970s, the United States National Spinal Cord Injury Statistical Center was established. Most Asian countries and regions do not have registries; therefore, it is challenging to evaluate epidemiological data in Asia. To date, there is no systematic analysis of the prevalence, sociodemographic distribution, and causes of spinal injuries across all provinces in China. Clinical studies in China were primarily single-center studies,[3] which were limited regarding reliable scientific findings and follow-up.

Given that causes of spinal injuries are frequently preventable, there is value in measuring the extent of different causes to understand the effect of prevention programs. This study used the data from Global Burden of Disease Study (GBD) 2019 and the data of 33 provincial-level administrative regions provided by the National Center for Chronic and Noncommunicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention (CDC) to analyze the incidence, prevalence, trends, causes, and regional distribution of spinal injuries in China from 1990 to 2019.

Methods Overview

We conducted this study using data from GBD 2019, which adopted a unified and comparable method to analyze the incidence and prevalence of 369 diseases and injuries in 204 countries and territories from 1990 to 2019. A detailed description of the background and content of this research can be found in GBD 2019; the relevant factors of spinal injuries were selected for the current analysis.[4] The data of 33 provincial-level administrative regions excluding Taiwan, China (including 31 provinces/autonomous regions/municipalities directly under the Central Government, Hong Kong and Macao Special Administrative Regions) were provided by CDC.

Definitions

Spinal injuries included spinal cord injuries at the neck level and below the neck level. For GBD 2019, the injury estimation process for non-fatal health outcomes encompassed 30 causes, including transport injuries, falls, drowning, self-harm, interpersonal violence, and animal contact.

Data sources

This study used the GBD method to analyze available demographic and epidemiological data at the provincial level in China. The Bayesian meta-regression tool DisMod-MR 2.1 was used as the primary estimation method to ensure the consistency among incidence, prevalence, and mortality rates in each case. The Chinese population census conducted every ten years (1990, 2000, and 2010) was the source of demographic data classified by age and gender. The standard population structure used for age standardization was derived from the estimated age structure of the population at the selected national level, with at least 5 million in each group.

The process of estimating incidence and prevalence was as follows. From the incidence estimates of each cause-nature combination, we used the proportion of individuals expected to experience short-term and long-term disability (the cutoff value of long-term disability is one year) to model the short-term and long-term estimates. The differential equation solver in DisMod-MR 2.1 was used to convert the incidence of causality to prevalence.

Data analysis

We analyzed the incidence and prevalence of spinal injuries in China in 1990 and 2019; then, compared them across the Group of 20 (G20, an international economic cooperation forum composed of 20 major economies, from which we excluded the EU from analysis and compared only 19 countries) and with the global average trends, also from the GBD dataset. The age-standardized incidence and prevalence were assessed in Chinese provinces in 1990 and 2019, and the proportion changes of primary causes were analyzed.

For each major cause, we estimated the changes in patient numbers from 1990 to 2019 attributable to population growth, population aging, and age-specific prevalence.[5] The observed change in the total number of patients equaled the net change of these factors. Two counterfactual scenarios were used for this decomposition analysis to calculate the number of patients.

We measured the most common causes of spinal injuries separately in terms of the original causes that led to the disability. Statistical codes for this study will be available upon publication via the Institute for Health Metrics and Evaluation. This study complied with the Guidelines for Accurate and Transparent Health Estimates Report recommendations.

Results

Based on the data from GBD 2019, from 1990 to 2019, the number of patients alive with spinal injuries increased by 138.32%, from 2.14 million to 5.10 million [Figure 1A], and the overall age-standardized prevalence increased from 0.20% (95% uncertainty interval [UI]: 0.18–0.21%) to 0.27% (95% UI: 0.26–0.29%) [Figure 1B], and both values increased after 2005. The age-standardized prevalence was higher in men than in women until 2019 (0.31% [95% UI: 0.29–0.33%] in men and 0.24% [95% UI: 0.22–0.26%] in women). Overall prevalence peaked at 65–69 years old in 1990 (65–69 years old in males and 75–79 years old in females [Figure 1C]), while the peak was 90–94 years old in 2019 (70–74 years old in males and 90–94 years old in females [Figure 1D]). The prevalence in females surpassed that in males in the 70–74 age group in 1990 and the 75–79 age group in 2019.

Figure 1:

Prevalence changes of spinal injuries in China. Trend of numbers (A) and age-standardized prevalence (B) of spinal injuries patients in the past three decades. Age-specific and sex-specific prevalence of spinal injuries in 1990 (C) and 2019 (D).

In 2019, the incidence in China was 16.47 (95% UI: 12.08–22.00, per 100,000 population), and the prevalence was 358.30 (95% UI: 333.96–386.62, per 100,000 population). The age-standardized incidence was 13.87 (95% UI: 10.15–18.66, per 100,000 population), and the age-standardized prevalence was 273.13 (95% UI: 255.11–294.39, per 100,000 population). From 1990 to 2019, the incidence of spinal injuries in China increased by 89.91% (95% UI: 72.39–107.66%), the most significant increase among the G20 countries, and was much higher than the global average of 5.59% (95% UI: −9.84% to 17.45%). The prevalence increased by 98.20% (95% UI: 89.56–106.82%), which was also the most significant increase and was higher than the global average of 25.52% (95% UI: 20.45–29.37%). The age-standardized incidence increased by 40.81% (95% UI: 32.92–49.14%), which was the most significant increase and was higher than the global average of –6.11% (95% UI: –17.29% to 1.51%). The age-standardized prevalence increased by 38.70% (95% UI: 34.71–43.15%), which was the second largest increase and was much higher than the global average of 5.82% (95% UI: 2.70–9.57%) [Supplementary Table 1, https://links.lww.com/CM9/B945].

Based on the data of 33 provincial-level administrative regions provided by CDC, from 1990 to 2019, the age-standardized incidence and prevalence in all provinces increased (not including data from Taiwan, China). In 2019, Zhejiang (22.08 [95% UI: 16.09–29.88] per 100,000 population), Shanghai (20.92 [95% UI: 15.40–28.08] per 100,000 population), and Jiangsu (18.69 [95% UI: 13.56–25.14], per 100,000 population) had the highest age-standardized incidence; Jilin (8.56 [95% UI: 6.27–11.40] per 100,000 population), Gansu (9.01 [95% UI: 6.62–12.02], per 100,000 population), and Xinjiang (9.14 [95% UI: 6.66–12.27], per 100,000 population) had the lowest age-standardized incidence. In 2019, Shanghai (454.38 [95% UI: 422.10–490.81], per 100,000 population), Zhejiang (428.76 [95% UI: 398.00–462.81], per 100,000 population), and Jiangsu (367.16 [95% UI: 341.04–395.28], per 100,000 population) had the highest age-standardized prevalence, while Jilin (176.34 [95% UI: 164.06–190.36], per 100,000 population), Xinjiang (182.58 [95% UI: 170.00–197.06], per 100,000 population), and Gansu (184.46 [95% UI: 171.84–197.61], per 100,000 population) had the lowest age-standardized prevalence. Sichuan had the most significant increase rate of age-standardized incidence (0.78 [95% UI: 0.67–0.90], per 100,000 population) and prevalence (0.82 [95% UI: 0.71–0.94], per 100,000 population) from 1990 to 2019.

The incidence of spinal injuries in China was 0.10 (95% UI: 0.08–0.13) million in 1990 and 0.23 (95% UI: 0.17–0.31) million in 2019, with a change rate of 128.21% (95% UI: 107.15–149.53%). The prevalence was 2.14 (95% UI: 1.98–2.31) million in 1990 and 5.10 (95% UI: 4.75–5.50) million in 2019, with a change rate of 138.16% (95% UI: 127.78–148.52%). In 1990, the incidence of spinal injuries in China was 8.67 (95% UI: 6.57–11.16, per 100,000 population) and 16.47 (95% UI: 12.08–22.00, per 100,000 population) in 2019, with a change rate of 89.91% (95% UI: 72.39–107.66%). The prevalence rate was 180.78 (95% UI: 167.53–195.35, per 100,000 population) in 1990 and 358.30 (95% UI: 333.96–386.62 , per 100,000 population) in 2019, with a change rate of 98.20% (95% UI: 89.56–106.82%) [Supplementary Table 2, https://links.lww.com/CM9/B945]. Although all numbers and rates were higher in males than in females, the change rate was more significant in females than in males.

The primary causes of spinal injuries in 2019 were falls and road injuries. From 1990 to 2019, the number of people with spinal injuries increased by 138.32%; the number caused by falls increased by 119.83%, and those by road injuries increased by 266.00%. The proportion caused by falls dropped from 54.20% (1.16/2.14 millions) to 50.00% (2.55/5.10 millions), while the proportion caused by road injuries increased from 23.36% (0.50/2.14 millions) to 35.88% (1.83/5.10 millions) [Table 1]. It is worth noting that falls were always the leading cause of spinal injuries and the increased proportion of road injuries.

Table 1 - Number and proportion of spinal injuries by cause in China in 1990 and 2019 and change rate of number from 1990 to 2019. Cause 1990 2019 1990–2019 change rate of number (%) Number (millions) Proportion (%) Number (millions) Proportion (%) Transport injuries Road injuries 0.50 23.36 1.83 35.88 266.00 Other transport injuries 0.09 4.21 0.13 2.55 44.44 Unintentional injuries Falls 1.16 54.20 2.55 50.00 119.83 Exposure to mechanical forces 0.04 1.87 0.10 1.96 150.00 Foreign body 0.09 4.21 0.09 1.77 0.00 Environmental heat and cold exposure 0.02 0.93 0.03 0.59 50.00 Other unintentional injuries 0.08 3.74 0.15 2.94 87.50 Self-harm and interpersonal violence 0.16 7.48 0.22 4.31 37.50 Total 2.14 100.00 5.10 100.00 138.32

The changes in the number of people with spinal injuries were accounted for by population growth, population aging, and changes in age-specific prevalence [Table 2]. From 1990 to 2019, 71.00% of the increase in people with spinal injuries could be explained by age-specific prevalence; the contribution to these changes by population aging was 47.00% and by population growth was 20.16%. Change in age-specific prevalence was the most significant factor in the increase in spinal injuries. Among the causes of spinal injuries, road injuries, exposure to mechanical forces, and falls had the most significant increase. Except for other transport injuries, foreign body, environmental heat and cold exposure, and self-harm and interpersonal violence, changes in age-specific prevalence from all other causes contributed to the increase.

Table 2 - Attribution analysis of changes in the number of people with spinal injuries, by cause in China, 1990 and 2019. Spinal injuries Transport injuries Unintentional injuries Self-harm and interpersonal violence Total Road injuries Other transport injuries Falls Exposure to mechanical forces Foreign body Environmental heat and cold exposure Other unintentional injuries No. of persons in 1990 (millions) 0.50 0.09 1.16 0.04 0.09 0.02 0.08 0.16 2.14 No. expected with 2019 population, 1990 population age structure, and 1990 prevalence (millions) 0.60 0.11 1.40 0.05 0.11 0.02 0.10 0.19 2.57 No. expected with 2019 population, 2019 population age structure, and 1990 prevalence (millions) 0.87 0.14 1.96 0.06 0.13 0.03 0.12 0.26 3.58 No. of persons in 2019 (millions) 1.83 0.13 2.55 0.10 0.09 0.03 0.15 0.22 5.10 Percentage change from 1990 because of population growth (%) 20.16 20.16 20.16 20.16 20.16 20.16 20.16 20.16 20.16 Percentage change from 1990 because of population ageing (%) 54.19 30.72 48.69 31.92 29.96 12.06 31.81% 46.81 47.00 Percentage change from 1990 because of change in age-specific prevalence (%) 191.26 –9.76 50.66 113.67 –51.31 –2.87 28.96 –23.91 71.00 Percentage change from 1990 to 2019 (%) 265.61 41.13 119.51 165.76 –1.19 29.35 80.93 43.07 138.16

The proportion of causes leading to spinal injuries by region is shown in Figure 2. Falls were the leading cause of spinal injuries, and road injuries were the second primary cause; however, road injuries were slightly highly prevalent than falls in Hebei, Shanxi, and Inner Mongolia. The prevalence caused by falls in Shanghai, Zhejiang, and Sichuan was the highest, while that in Xinjiang, Gansu, and Jilin was the lowest. Road injuries in Jiangsu, Zhejiang, and Shanghai were the highest in number, while those in Xizang, Guangxi, and Xinjiang were the lowest.

Figure 2:

Prevalence of spinal injuries by causes in 33 provincial-level administrative regions of China, 2019. *not including data of Taiwan, China.

Discussion

From 1990 to 2019, the number of living patients with spinal injuries and the age-standardized prevalence increased. The incidence and prevalence in China significantly increased among the G20. Prevalence was high in middle-aged and older adults, especially for older adult females. These findings suggest that spinal injuries have become a significant public health problem in China.

China is one of the largest developing countries worldwide, with rapid economic and social development and a large population. In the past three decades, the age structure in China has significantly shifted, indicating a substantial challenge to the aging society regarding the prevention and control of spinal injuries. In the present study, although incidence and prevalence were higher in males than in females, the change rate was more significant in females than in males. In most countries,[3] women historically stayed home and were protected from outside dangers, whereas men were more likely to be engaged in dangerous work to support the family. This feature was a significant reason why men were more vulnerable to injury. Violence and alcohol are also significant explanations for the higher incidence in men than in women.[6] However, as societies develop, an increasing number of women perform high-risk jobs, and longer life expectancy makes older women more likely to fall. These are possible reasons for the more significant change rate in women.

In comparison with other countries, China has unique characteristics: one of the biggest developing countries in the world, rapid economic and social development, and large population. The substantial geographical variability in the occurrence of spinal injuries in our study is notable. Age-standardized incidence and prevalence for spinal injuries were highest in developed provinces of Eastern China, like Zhejiang, Shanghai, and Jiangsu provinces. As in global, age-standardized incidence and prevalence were also highest in high socio-demographic index regions, especially western Europe and high-income Asia Pacific.[7,8] These regional differences could be accounted for several possible explanations. First, nowadays, eastern regions of China are generally more socioeconomically developed and have higher proportions of people living in urban areas compared with western China. Population concentration, traffic congestion, developed industry, and construction in eastern regions are all objective factors that contribute to a higher incidence of spinal injuries. Although road conditions in developed regions are better, higher vehicle ownership makes road injuries-related spinal injuries more serious.[9] Second, population aging is nowadays a critical problem all over the world. The number of elderly persons in China also continues to grow, with an expected 329 million older than 65 years and 120 million older than 80 years by the year 2050. In the developed eastern regions, the longer life expectancy and more demand for outdoor activities lead to higher risks for falls,[10] which might differ greatly from the impoverished areas in the western regions. Third, there are significant differences of geographical environment in China. For example, people lived in the vast western areas do not require agricultural labor and mainly engage in indoor activities during the long winter; so, the risks for spinal injuries are relatively low. In conclusion, the discrepancy in local economic development, road conditions, culture, lifestyle, and environment could account for the geographical variability.

From 1990 to 2019, the number of people with spinal injuries increased by 138.16%, and 71.00% of the increase could be explained by age-specific prevalence, suggesting that the increase in the absolute number of individuals with spinal injuries was due to the increases of age-specific prevalence, rather than the aging of the population or the increase of the population. Therefore, the prevention and control of related risk factors appear more urgent. Considering specific reasons, road injuries, exposure to mechanical forces, and falls had the most significant population increase caused by the increases in age-specific prevalence. In contrast, the aging of the population caused the increase in population for other reasons. Foreign body was the only injury that caused a decrease in patient number.

In 2019, falls were the leading cause of spinal injuries, accounting for over half of all causes. With the aging of societies, falls have become major public health problems for communities worldwide, leading to expanding healthcare expenses.[11,12] Approximately one-third of all community-dwelling people aged 65 years or older fall once a year, increasing to 50% in persons aged 80 years or older.[13] Road traffic accidents were the leading cause in developed countries, while falls accounted for the majority in developing nations.[14] In China, there was an enormous number of older adult patients with degenerative cervical spine changes who were more vulnerable to slight damage (e.g., a low-height fall); therefore, the number of low fall-induced spinal injuries would increase. Chronic complications related to prolonged bed rest after fall injuries, including deep venous thrombosis, hypostatic pneumonia, pressure ulcers, and urinary tract infection, substantially increasing mortality. Due to the burden caused by falling and positive results from prevention interventions, enhanced preventive measures should be the priority of health policy.[15] Risk factors for falls in older adults include internal factors (e.g., physiology, pathology, drugs, and psychology), environmental factors (e.g., lighting, road surface, support facilities, and walking aids), and social factors (e.g., health care level, safety design of the outdoor environment, and living alone). Given these reasons, the control and prevention of falls in older adults should be a social system.

In 2019, road injuries remained the second leading cause of spinal injuries, accounting for over one-third of all causes. Significant injuries from road traffic accidents are likely secondary to poor road infrastructure, inadequate safety legislation and law enforcement in low- and middle-income countries. China has built the world’s largest high-speed rail network,[16] and private motor vehicle ownership is increasing rapidly, numbering 123.4 million.[17] The rapidly increasing number of vehicles has led to a growing number of inexperienced drivers, low seat belt use, and poor road design with inadequate separation among pedestrians, cyclists, and motor vehicles, leading to many accidents and injuries.[18,19] Transportation-related risk factors, such as speeding and drunk driving, are significant sources of morbidity and mortality in China, and they have profound effects on public health. Protective technologies and associated policies for transport injuries in China include enforced use of seatbelts and child restraints in vehicles, helmet wearing, alcohol locks, and others. On the other hand, accident injury risk is aggravated by inadequate emergency response systems and trauma care. Taking advantage of China’s infrastructure and healthcare resources is critical to establishing effective regional rescue and treatment systems.[20] One path forward would be establishing trauma rescue and treatment networks, each comprising one trauma center in a qualified general hospital, with trauma rescue and treatment stations in nearby secondary hospitals in specific areas.[21]

Several strengths of our study are worth noting. First, this is the first study to describe epidemiological characteristics of spinal injuries in China and to analyze the impact according to age, sex, and geographical location. Second, this study demonstrated the severe disease burden of spinal injuries across all the provinces in China. Third, we noted that falls and road injuries were the most significant causes. This study, therefore, provides valuable information on the burden of spinal injuries on society in China and should guide healthcare providers and policymakers as they develop appropriate prevention and control strategies.

The current study is subject to all the limitations of GBD studies. First, GBD 2019 estimated the models of primarily spinal injuries through available provincial-level data and previous studies in China. The absence of relevant data in some provinces and the failure to differentiate between urban and rural areas might have led to bias in the model estimates. Second, the rate of spinal injury diagnosis could have varied over the study period, making interpreting secular trends difficult. Third, there are many causes of spinal injuries, and it would be challenging to analyze all potential causes in detail; therefore, the interpretation of some results might be compromised.

In conclusion, spinal injuries are significant public health problems in China. Public health policies should focus on preventive strategies against falls (especially for older adults) and road traffic safety. The uneven distribution across provinces requires customized intervention strategies. Finally, registry and emergency response systems for spinal injuries must be improved in China.

Funding

This study was supported by grants from the National Key R&D Program of China (No. 2022YFB4703000) and Major Health Special Project of the Ministry of Finance of China (No. 2127000277).

Conflicts of interest

None.

References 1. Selvarajah S, Hammond ER, Haider AH, Abularrage CJ, Becker D, Dhiman N, et al. The burden of acute traumatic spinal cord injury among adults in the United States: An update. J Neurotraum 2014;31:228–238. doi: 10.1089/neu.2013.3098. 2. Cripps RA, Lee BB, Wing P, Weerts E, Mackay J, Brown D. A global map for traumatic spinal cord injury epidemiology: Towards a living data repository for injury prevention. Spinal Cord 2011;49:493–501. doi: 10.1038/sc.2010.146. 3. Ning GZ, Yu TQ, Feng SQ, Zhou XH, Ban DX, Liu Y, et al. Epidemiology of traumatic spinal cord injury in Tianjin, China. Spinal Cord 2011;49:386–390. doi: 10.1038/sc.2010.130. 4. GBD 2019 Diseases and Injuries Collaborators. Global burden of 369 diseases and injuries in 204 countries and territories, 1990-2019: A systematic analysis for the Global Burden of Disease Study 2019. Lancet 2020;396:1204–1222. doi: 10.1016/S0140-6736(20)30925-9. 5. GBD 2015 Mortality and Causes of Death Collaborators. Global, regional, and national life expectancy, all-cause mortality, and cause- specific mortality for 249 causes of death, 1980-2015: A systematic analysis for the Global Burden of Disease Study 2015. Lancet 2016;388:1459–1544. doi: 10.1016/S0140-6736(16)31012-1. 6. Chen CF, Lien IN. Spinal cord injuries in Taipei, Taiwan, 1978-1981. Paraplegia 1985;23:364–370. doi: 10.1038/sc.1985.58. 7. GBD 2016 Traumatic Brain Injury and Spinal Cord Injury Collaborators. Global, regional, and national burden of traumatic brain injury and spinal cord injury, 1990–2016: A systematic analysis for the Global Burden of Disease Study 2016. Lancet Neurol 2019;18:56–87. doi: 10.1016/S1474-4422(18)30415-0. 8. Ding W, Hu S, Wang P, Kang H, Peng R, Dong Y, et al. Spinal cord injury: The global incidence, prevalence, and disability from the Global Burden of Disease Study 2019. Spine 2022;47:1532–1540. doi: 10.1097/BRS.0000000000004417. 9. Van den Berg ME, Castellote JM, Mahillo-Fernandez I, de Pedro-Cuesta J. Incidence of spinal cord injury worldwide: A systematic review. Neuroepidemiology 2010;34:184–192. doi: 10.1159/000279335. 10. Thompson C, Mutch J, Parent S, Mac-Thiong JM. The changing demographics of traumatic spinal cord injury: An 11-year study of 831 patients. J Spinal Cord Med 2015;38:214–223. doi: 10.1179/2045772314Y.0000000233. 11. Kannus P, Parkkari J, Koskinen S, Niemi S, Palvanen M, Järvinen M, et al. Fall-induced injuries and deaths among older adults. JAMA 1999;281:1895–1899. doi: 10.1001/jama.281.20.1895. 12. Meerding WJ, Mulder S, van Beeck EF. Incidence and costs of injuries in The Netherlands. Eur J Public Health 2006;16:272–278. doi: 10.1093/eurpub/ckl006. 13. Stalenhoef PA, Crebolder HFJM, Knotnerus JA, van der Horst FGEM. Incidence, risk factors and consequences of falls among elderly subjects living in the community. Eur J Public Health 1997;7:328–334. doi: 10.1093/eurpub/7.3.328. 14. Chiu WT, Lin HC, Lam C, Chu SF, Chiang YH, Tsai SH. Epidemiology of traumatic spinal cord injury: Comparisons between developed and developing countries. Asia Pac J Public Heal 2016;22:9–18. doi: 10.1177/1010539509355470. 15. Tinetti ME, Kumar C. The patient who falls: “It’s always a trade-off”. JAMA 2010;303:258–266. doi: 10.1001/jama.2009.2024. 16. Zhang J, Mauzerall DL, Zhu T, Liang S, Ezzati M, Remais JV. Environmental health in China: Progress towards clean air and safe water. Lancet 2010;375:1110–1119. doi: 10.1016/S0140-6736(10)60062-1. 17. National Bureau of Statistics of China. China Statistical Yearbook. Beijing: State Council of the People’s Republic of China, 1996-2015. 18. Wang SY, Li YH, Chi GB, Xiao SY, Ozanne-Smith J, Stevenson M, et al. Injury-related fatalities in China: An under-recognised public-health problem. Lancet 2008;372:1765–1773. doi: 10.1016/S0140-6736(08)61367-7. 19. Wismans J, Skogsmo I, Nilsson-Ehle A, Lie A, Thynell M, Lindberg G. Commentary: Status of road safety in Asia. Traffic Inj Prev 2016;17:217–225. doi: 10.1080/15389588.2015.1066498. 20. Jiang B, Liang S, Peng ZR, Cong H, Levy M, Cheng Q, et al. Transport and public health in China: The road to a healthy future. Lancet 2017;390:1781–1791. doi: 10.1016/S0140-6736(17)31958-X. 21. Wang TB, Yin XF, Zhang PX, Kou YH, Jiang BG. Road traffic injury and rescue system in China. Lancet 2015;385:1622. doi: 10.1016/S0140-6736(15)60794-2.