Introduction
Hip fracture is one of the most devastating consequences of osteoporosis [
1,
2] and is becoming one of the most important public health problems in the world [
3]. Femoral intertrochanteric fracture and femoral neck fracture are the two main types. Hip fracture is regarded as a result of demographic aging, and age is the major risk factor for mortality in patients with hip fractures [
4,
5]. Hip fractures can exact a terrible toll on the elderly and lead to severe complications and high mortality due to their severity and high economic cost [
6,
7]. Therefore, many researchers have been paying increasing attention to mortality from hip fracture in the past two decades [
8].
Data about the mortality risk and rates of hip fractures are available abroad and have contributed to the efforts and attention that national and local policymakers have devoted to improving patients’ healthcare quality and safety [
9]. However, data about mortality rate after hip fracture in mainland China remain limited and localized. To our best knowledge, population-based studies on a national basis have never been conducted due to the difficulty of comprehensive inclusion of populations in a country of 1.3 billion people with different regional, racial, and ethnic groups, and the lack of these studies has hindered our understanding of the disease and adversely affected healthcare quality and safety. Fortunately, a growing number of population-based studies about the 1-year mortality rates after hip fracture were conducted in local areas in mainland China during the years 2000 and 2018. These studies were restricted to specific geographic and demographic features and could not represent the overall Chinese population. However, it is feasible to conduct a systematic synthesis of the data from population-based studies and explore the 1-year mortality rates after hip fracture from an epidemiological modeling approach.
In this study, we undertook a comprehensive systematic review and meta-analysis to analyze the 1-year mortality rates after hip fracture, femoral intertrochanteric fracture, and femoral neck fracture between years 2000 and 2018. We also aimed to develop epidemiological models to reveal the variations in 1-year mortality rate by age for hip fracture, femoral intertrochanteric fracture, and femoral neck fracture based on these data from mainland China.
Discussion
It is widely known that hip fracture is one of the most relevant fractures in terms of its high mortality [
7]. It has been reported that having a hip fracture can cause excess mortality and that there is a greater mortality risk for patients with hip fracture than for those without hip fracture [
6,
14]. There have been different results reported for the 1-year mortality rates after hip fracture. Haleem et al. [
15] reported that the 1-year mortality rates were 22 to 29% from 1996 to 1998, while one single center survey [
16] noted a 1-year mortality rate of 40% in American nursing home residents between 1999 and 2006. Abrahamsen [
17] and Hu [
18] performed meta-analyses and found that the mortality rates at 1 year were 5.9~59% and 24.5%, respectively. The 1-year mortality rate after hip fracture in Canadian nursing home residents was reported at approximately 45% in 2008 and 2009 [
19]. In Asian populations, the 1-year mortality rates were also different: 17.8% in Korean women [
20], 18.65% in Hong Kong [
21], and 13.5% in Taiwanese women [
22]. In mainland China, the local survey rate [
23] regarding 1-year mortality in Beijing was approximately 23.44% in total. However, the result in Beijing could not represent the overall mortality in mainland China due to the unbalanced health care services between areas.
We performed this meta-analysis and systematic review based on the rigorous reviews of existing evidence on hip fracture mortality in mainland China. We calculated the 1-year mortality rates after hip fracture, femoral intertrochanteric fracture, and neck fracture in general Chinese populations between the years 2000 and 2018 and explored the variations with the age factors. The 1-year mortality rate after intertrochanteric fractures was higher than the femoral neck fracture (17.47% vs 9.83%), and the overall 1-year mortality rate after hip fracture was 13.96% in mainland China. Our study also estimated the age-specific mortality rates for the median year of every 5-year age group and revealed that advanced age was a significant risk factor for mortality. The 1-year mortality rate after hip fracture was the highest at 28.91% in the age group 95 to 99 years old and the lowest at 2.65% in the age group 50 to 54 years old. The strong association between the mortality rate and the age was consistent with other studies [
6,
14]. Keene et al. [
24] proposed that 1-year mortality would increase by 1% with a 1-year increase in age.
We also found that the 1-year mortality rate was higher after femoral intertrochanteric fracture than femoral neck fracture in every 5-year age group when the age was over 60 years old. The relationship between fracture type and mortality remains controversial, with some investigators [
25] reporting that the fracture type did not affect the mortality while some survival studies [
26,
27] revealed the mortality rates of intertrochanteric fracture patients were higher than femoral neck fracture patients. However, patients with intertrochanteric fractures were older than those with a femoral neck fracture in the previous studies. Whether the excess mortality in these studies reflects differences in age or the fracture types remains to be clarified. In our study, we compared the 1-year mortality rates between the femoral intertrochanteric fracture and neck fracture in the same age groups and found that the mortality rates were higher in those with intertrochanteric fracture, which suggested that fracture type might be one predictor of mortality in hip fracture patients. However, we did not compare the differences of the sex, comorbidities, anesthesia type, or other factors between the two fracture types in the same age group. These factors can also contribute to mortality after a hip fracture [
14,
44].
The 1-year mortality rates in mainland China were lower than that in Canada, the USA, and most other regions in Asia mentioned above [
19‐
22]. Different countries and races have different nutritional habits [
23] and different physical exercise habits [
28], which could cause differences in mortality. In addition, we should also take ethnic genetic variations into consideration. Some studies [
29,
30] have demonstrated a relationship between bone mass and ethnic genes, showing that on average blacks have greater bone mass than whites and that Asians have the lowest bone mass among these races. Walker and colleagues [
31] also indicated genetic differences in osseous microarchitecture in Chinese–American patients. However, there are few studies about the influence of special ethnicity on prognosis differences after hip fracture [
32]. Although some studies [
33,
34] have shown that black patients are at greater risk for mortality, others [
35] did not reach the same conclusions. Therefore, it remains unclear whether the genetic variations between Chinese populations and others could affect the mortality rate after hip fracture.
In addition to the ethnic genetic variations, we should pay more attention to the impact of cultural and economic differences between different ethnic groups on mortality after hip fracture. The fact that Chinese cultural attitudes regarding hip fracture is different from others is manifested in several respects. On the one hand, the attitude towards the disease reflects cultural differences. Attitudes towards hip fracture might prolong the wait time for surgery, which has been demonstrated to be associated with a poor prognosis after hip fracture [
36]. The delayed phenomenon is common in mainland China due to geographic and economic factors and may play an important role in mortality rates. On the other hand, we hypothesize that the reason the mortality rates were lower in mainland China than in the USA results from the higher mortality rates in nursing home residents [
37,
38]. Elderly Chinese people are unwilling to separate from their children and to live in nursing homes because of their traditional cultural attitudes and the low quality of care in nursing homes. Consequently, community dwellers make up a large part of the elderly Chinese people, whose fracture rates are lower than that of nursing home residents [
37,
38]. Therefore, different proportions of nursing home residents would lead to different mortality rates in different races and nations.
The economy undoubtedly has an important impact on the prognosis of diseases. Economic pressure poses challenges for China and other low-income countries in improving the medical resources and care quality [
39]. It has been proposed that patients from economically disadvantaged areas are predisposed to delayed surgery for hip fracture, which would increase the mortality rates [
37]. China has been undergoing rapid economic development in the past two decades [
39]. The annual disposable income in urban and rural areas in 2008 was 3.0 and 2.2 times higher than that in 1998, respectively [
39,
40], which results in a decrease in the morbidity and mortality of diseases. Nevertheless, it is still under debate whether socioeconomic status has an impact on mortality after hip fracture. Studies from the UK noted that lower socioeconomic status was relevant to higher mortality risk after hip fracture [
41,
42], while investigators in the USA disagreed with these viewpoints [
43].
To our knowledge, this is the first review to provide complete data regarding hip fracture mortality rates in mainland China. We conducted a comprehensive literature search and used a strict approach to include studies in order to reasonably cover the Chinese population in mainland China. The information bias due to selection and methodological heterogeneity was reduced to the minimum. The estimated results were representative for mainland China with a wide geographical scope covering all six geographic regions of China. We also constructed the epidemiological model to reveal the relationship between the age and mortality. This is the first time anyone has applied this epidemiological model to assessing the mortality of diseases. We found that age was a significant risk factor for the mortality rate, and we found that the mortality rates after femoral intertrochanteric fracture were higher than femoral neck fracture when the age group was the same. From a public health management perspective, these data can help to identify the prognosis after hip fracture in mainland China and help policy makers to allocate medical resources appropriately for hip fracture.
Our study is still subject to some potential limitations. First, heterogeneity was significant among the included studies although we used a rigorous selection approach. To explain the significant heterogeneity, we conducted meta-regression to examine the group-level variables, age, setting (urban, rural, and mixed), geographic region, study type (prospective or retrospective cohort study), and survey year, but could not explore the impact of individual-level variables because of the lack of information, for example, in regard to the sex [
14], comorbid conditions [
44], wait time for surgery [
36], postsurgery complications [
37,
45], advanced cognitive impairment [
45], and increased baseline ADL (activities of daily living) [
45]. The varied quality of the studies involved could also contribute to the heterogeneity. Second, publication bias was observed when analyzing the studies about hip fracture although the estimated results changed only a little after applying the trim and fill method. On the one hand, the publication bias might derive from the significant heterogeneity between the included studies. On the other hand, we could not avoid the absence of unpublished studies, which might lead to bias in the final estimates. Third, although 22,817 Chinese individuals were involved in our study, this number might be inadequate for one country with a population of 1.3 billion people. We did not include certain provinces, municipalities and autonomous regions such as Qinghai Province and the Inner Mongolia autonomous region. The mortality in these regions might have an impact on the results. Fourth, as mentioned above, there is a difference in mortality between nursing home residents and community dwellers. However, the studies included in the meta-analysis did not differentiate between nursing home residents and community dwellers, which could overestimate the mortality rates for community dwellers. Fifth, the studies included were based on patients admitted to the hospital, which would lead to missing those who were not admitted to hospitals with hip fracture and would result in selection bias.
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