Epidemiological Features of Spinal Cord Injury in China: A Systematic Review

Background: Spinal cord injury (SCI) is a severe condition that disrupts patients' physiological, mental, and social well-being state and exerts great financial burden on patients, their families and social healthcare system. This review intends to compile studies regarding epidemiological features of SCI in China. Methods: Searches were conducted on PubMed, EMBASE, Web of Science and Cochrane Library for relevant studies published through January, 2018. Studies reported methodological and epidemiological data were collected by two authors independently. Results: Seventeen studies met the inclusion criteria. Two studies reported incidence of SCI that is 60.6 in Beijing (2002) and 23.7 in Tianjin (2004–2008). All studies showed male had a larger percentage in SCI compared to female except Taiwan (2000–2003). The average male and female ratio was 3–4:1 in China and the highest male and female ratio was 5.74: 1 in Tianjin (2004–2007). Farmers, laborers and unemployed people accounted for more than half of the SCI patients in China. Fall was the primary causation with exception of Heilongjiang (2009–2013), Beijing (2001–2010), and Taiwan (2002–2003), where motor vehicle collision (MCVs) was the leading causation. Pulmonary infection, urinary tract infection and bedsore were common complications, accounting for approximately 70% of SCI patients in China. Conclusion: This review shows that epidemiological features of SCI are various in different regions in China and prevention should be implemented by regions. The number of patients with SCI result from fall and MCVs may become a main public health problem because population aging and economic developing in China. However, because all included studies were retrospective and lacking a register system in China, some data were incomplete and some cases may be left out, so the conclusion may not be generalizable to the other regions.

worldwide with annual estimated incidence at 10.4-83 cases per million even though prevention measures have been taken to lower the occurrence (3,4). The incidence of SCI range from 20.7 to 83.0 in North American and 8.0 to 130.6 in Europe per million annually (5,6). Research have reported the incidence of SCI ranged between 10.6 and 22.6 per million in Québec, Canada (2000-2011) (7) and its annual costs was 2.67 billion dollars. In Denmark (1990Denmark ( -2012 (8) (10). It has been estimated the costs of SCI in Australia annually to be almost 2 billion Australian dollars in total (11). In Japan, it has been reported the incidence of SCI was 121.4 per million in 2011 and 117.1 in 2012 (12). The financial burden of SCI includes rehabilitation services, expensive personal assistance, lost productivity for disability and social isolation. Studies have revealed the high incidence and heavy economic impact of SCI in developed countries.
As the largest developing country with approximately 25% of the global population, China has a large number of SCI patients. Unfortunately, little was known about the epidemiological features especially incidence and prevalence of SCI (13). Given the increasing life expectancy people with SCI are experiencing from 69 years in 1990 to nearly 75 years (14), prevention strategies and post-injury rehabilitation is crucial (15). Reliable epidemiological data and evidence of SCI in China are vital for estimating the number of patients, finding out the main causes, developing interventions, providing up-to-date information, and raising public awareness. Previous studies have reported the incidence of SCI in China increased significantly (16). Therefore, it is of great significance to review all the research data of SCI in China to attain a comprehensive understanding of its epidemiological features so as to improve management and reduce the financial burden on patients and healthcare system. This review intends to compile the studies regarding epidemiological features of SCI published through January, 2018 in four directly governed cities-Beijing, Tianjin, Shanghai and Chongqing, and four provinces-Heilongjiang, Anhui, Guangdong and Taiwan. It will provide an updated overview for the epidemiological profile and give an insight into current situation of SCI in China. This can help us better carry out prevention strategies and effective allocate medical resources.

METHODS
Searches were conducted on PubMed, EMBASE, Web of Science and Cochrane Library for potentially relevant studies without language and date restrictions. The keywords and phrases applied for this search were "spinal cord injury, " "traumatic spinal cord injury, " "epidemiology, " and "China." Bibliographies of included studies were also systematically screened to identify further relevant studies which were not included in the searched electronic databases. Case reports and conference abstracts were excluded. Figure 1 displays the search strategy and screen procedure in details. Titles and abstracts were identified by two independent reviewers and were categorized by the previous inclusion criteria. The eligible inclusion criteria were presented as follow: (1) original study concerning SCI or TSCI; (2) studies provide relevant epidemiological data; (3) original data were collected from hospital. Results extraction was also conducted by two independent reviewers and all discrepancy were settled by discussing with a third reviewer. From included studies, methodological information and epidemiological data were collected: region, source population, incidence period, case criteria, study type (prospective or retrospective), total number of patients, incidence, causation, male and female ratio, mean age, age with peak incidence, age span, patients' occupation, injury level, injury extent, America Spinal Injury Association Impairment Scale (AIS) grade. Additionally, complication and treatment were extracted.

RESULTS
Total 152 potentially relevant studies were identified initially and 15 met the inclusion criteria. After systematically screening bibliographies of included studies, two additional were added. Therefore, a total of 17 studies were included finally. The epidemiological features of eight regions (Figure 2) were reported. Table 1 displays region, patient source, incidence periods, diagnostic criteria and study type, and number of patients, incidence, causation, male and female ratio, average age, peak incidence age and age span were listed in Table 2. Table 3 summarizes the occupation, causation, level of injury, ASI degree and treatment. Tables 4-8 present causation, occupation, segments, severity and complication, respectively.

Occupations
As shown in Table 5, the occupations of SCI patients varied including the farmers, laborers, civil servants, office clerks, students, teachers, retired, unemployed and others. Classification of their occupations on the basis of their workplace. It was evident that farmers, laborers and unemployed people had a higher risk of SCI. These three groups accounted for more than half of the patients with SCI. In Beijing
The main treatment for SCI was surgery, including decompression and internal fixation or fuse. In the included studies, more than half of the SCI patients received surgery.
Nevertheless, a larger proportion of patients (63.3%) in Beijing (2002) received conservative treatment than surgery (36.7%) (17). In addition, a much larger percentage of patients in Guangdong (2003Guangdong ( -2011.7%) received rehabilitation than other regions in China (25). Rehabilitation strategy including braces can be used to practice standing and walking, and other special tools, such as walking aids, can be provided to compensate for the lack of moter funcion.

DISCUSSION
SCI impairs the physical, metal, and social well-being state of patients and exerts heavy financial burden on national healthcare system, patients and their families. A thorough understanding of SCI epidemiological profile helps national healthcare system carry out preventative strategies better and allocate medical resource reasonablely. Also, a comparison between different cities and provinces can shed light on how to effectively tackle these issues in the process of implementing prevention measures.  Many studies of SCI were carried out in developed nations, especially in America, Canada and Australia. Developing countries, however, with approximately 80% population throughout the world, lack related data because a national register system for SCI has not been established yet. To the best of our knowledge, several reviews of SCI in China have been reported. In China, it is difficult to estimate incidence because universal diagnostic criteria and national register system were not established. In this study, only 2 studies reported estimated incidence. In 2002, the incidence in Beijing was 60.6 per million, while it was 23.7 per million in Tianjin (2004-2008) (21,28). Studies in China used various inclusion criteria, so the incidence varied significantly. In developed countries, the annual incidence was 20.7-83 per million in America and 8.0-130.6 in Europe (34). This indicate the incidence of SCI in China was similar with developed countries. And other studies have reported developing regions had lower incidence compared to developed countries (35) and such difference might due to the development level of society and economy. In Europe and American, people are more likely to participate in risky activities like housing riding, rugby and skiing and these are high risk factors of SCI. In China, ages with peak incidence is different from other countries. Ages with peak incidence was varied from 30 to 60 years, while it was 20-29 in Aragon, Spain (1972-2008) and 16-31 in Thessaloniki, Greece in 2006 (36,37). In Beijing (1993-2006), peak age of patient was 12-29, which is younger than other studies because it focud on sports related SCI and most athletes were young people. In addition, the mean age of SCI in North America was range from 32 to 55.4 years (38), and it was between 37 and 47.9 in Europe (39). This was in consistence with mean age in China, which is from 30 to 50. Demographic structure is a main factor to explain varied ages with peak incidence across different countries. In China, the ratio of old people is increasing dramatically. It has been predicted individual aged over 60 could be 438 million by 2050 (40). Old people are more vulnerable to SCI due to degeneration of vertebrae and deterioration of physical conditions, so prevention is of great importance. The elderly should aware of the potential risks and take precautionary measures, such as do not do strenuous exercise and go to hospital regularly for physical examinations.
Most studies showed that male were at higher risk of SCI than female (41,42), these results were in accordance with present study in China. The ratio up to 5.71:1 in Tianjin . This was ascribed to the Chinese traditional cultural backgrounds. Male are major sources of household income and take the responsibility to support their families while female have to stay at home and take care of children. Meanwhile, male are the main labor resources and productive group of society and many engage in manual work. Thus, a large number of male work on high risk industry and thay are more likely to be exposed to risky environment, such as industrial construction sites. However, with the progress of society, more female are  taking high risk occupation, it could cause a slightly increase of female patients with SCI. In Beijing and Shanghai, the ratio was relatively lower because male and female nearly have equal access to various jobs in big cities. It was reported in Yang et al. (25) that the mean age of SCI patients was 41.6 (14.7) and age group of 41-60 had most injuries, but this was inconsistent with the high percentage of students (44.3%), which was much higher than worker (5.1%), and we can not explain this inconsistency. Traffic accidents and falls are main causes of SCI in developed countries (43)(44)(45). People in these countries usually have a private car and this cause a high rate of car accidents. Old people living alone are prone to fall when walking up and down stairs. Similarly, MVCs and fall were the two leading cause in different regions in China (40). With the development of economy in China, most people had a private car and this led to the significant increase of car accidents, and disabilities caused by traffic accidences can be reduced through improve vehicle safety, driver behavior and road conditions (46). Chongqing is called "mountain city" in China and the city is in mountains, so the incidence of fall was high. In Guangdong, Yang et al. (25) reported fall was leading cause, while Yang et al. (33) reported MCVs was the most common cause. These 2 studies based on different populations, so they got different conclusion. In Yang et al. (25) included 1340 cases, while 3,832 cases in Yang et al. (33). Low fall resulted in a large proportion of SCI as people aging. With social progresses and lifestyle changes, increasing number of old people pay more attention to their health conditions and engage in various activities, lacking of protective measures and experiences could increase risks of SCI. In some Western Asia countries, gunshots and violent conflicts account for a large proportion of SCI because people are accessible to firearms (47)(48)(49). SCI can cause sensory or motor deficit and bladder dysfunction, so patients have high risks of complications. Pulmonary infection, urinary tract infection (UTIs) and bedsore are common complications, accounting for approximately 70%. Pulmonary infection in Guangdong (2003-2011) was high, which (33) and nearly twice as high as Tianjin (2008)(2009)(2010)(2011). This because patients with high leval cervical SCI require mechanical ventilation but poor management will develop ventilator associated pneumonia. Besides, ability to cough is impaired due to paralysis of breathing muscles and it can cause pulmonary infections. UTIs in SCI patient are high both in high-income countries and less developed countries (50,51) because patients who have bladder dysfunction have to use catheterization as a management method. The incidence of UTIs was high in Tianjin (2008-2011) and Guangdong (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011). Evidences have shown that the methods of bladder management and different catheter material might relavant to UTIs (50). Other factors such as personal hygiene and long-term apply of indwelling catheter are associated with UTIs. Education on catheterization techniques and care can reduce and avoid UTIs. In addition, patients with SCI are more likely to suffering from bedsore due to sensation and mobility impair. Patients with bedsores were high in Guangdong (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)15.4%) and Tianjin (2008)(2009)(2010)(2011)9.8%) (20,25). Hospitals and rehabilitation centers should provide patients with careful management to prevent it, such as turn over frequently and skin checks on daily basis. Meanwhile, patients and their family members need training for nursing techniques to avoid bedsore. Furthermore, patients with SCI easily develop deep venous thrombosis (DVT). The percentage of DVT was reported in Tianjin (2008-2011) and in Guangdong (2003-2011), which needs rapid antithrombotic therapy to prevent potential pulmonary embolism. Electrolyte disturbance can be caused by methylprednisolone administration. It is controversial to use methylprednisolone currently but high dose use within 8 h after SCI is considered as a treatment option in China (52).
Studies have showed that surgery is the main treatment especially for complete injuries because it can prevent further injuries and improve spinal cord conditions (17,19,23,(25)(26)(27)33). But weather perform surgery was depend on the severity and extent of injuries. Moreover, some patients chose conservative therapy while others against medical advice and left. Importantly, long term rehabilitation therapy is necessary for further functional recovery. Physical therapy is the main rehabilitation therapy and it based on functional training like standing and walking practice. Nursing and medication are also used to prevent complications in rehabilitation centers. Rehabilitation center was advanced in high income countries, whereas it is not well built in China.
Despite increasing number of literature was published, it was little research that summarize all the studies so as to further investigate the epidemiological features of SCI in China. This review tries to provide a more detailed epidemiological profile of SCI in China, but challenges should not be neglected. First, there is no standard diagnosis criteria in China, so most patients in studies are diagnosed by clinical and image criteria. Second, all studies were retrospective. Therefore, some data were incomplete or inaccurate. Third, lacking a register system in China, some cases meet the included criteria may not be included. Forth, conclusion may not be generalizable to the other regions.

CONCLUSION
Overall, this review summarizes studies and provides a upto-date epidemiological features of SCI in China. Because the existence of limitations, it is challenging to obtain exact epidemiological data of SCI. Thus, more studies are needed to provide large amount of data and evidence. In addition, it is impeative to establish a national register system for SCI patients in the next few years and it will be helpful for throughtly understanding the epidemiological features of SCI in China.