Journal of Geriatrics and Palliative Care

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Research Article

Epidemiology of Physical Function Impairment in Global Chinese Aging Population: A Systematic Review

XinQi Dong* and Dan Su

  • Rush Institute for Healthy Aging, Rush University Medical Center, Chicago, Illinois, USA
*Address for Correspondence: XinQi Dong, Professor of Medicine, Nursing and Behavioral Sciences Director, Chinese Health, Aging and Policy Program Associate Director, Rush Institute for Healthy Aging, Rush University Medical Center, Chicago, Illinois, USA, Tel: 312 942 3350; Fax: 312 942 2861; E-mail: xinqi_dong@rush.edu
 
Citation: Dong X, Su D. Epidemiology of Physical Function Impairment in Global Chinese Aging Population: A Systematic Review. J Geriatrics Palliative Care 2016;4(1): 23.
 
Copyright © 2016 Dong X, et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
 
Journal of Geriatrics and Palliative Care | ISSN: 2373-1133 | Volume: 4, Issue: 1
 
Submission: 22 February 2016 | Accepted: 26 April, 2016 | Published: 3 May 2016

Abstract


 
Background: Physical function is a cornerstone of geriatric medicine. Impairment in physical function may threaten one’s ability to live independently and is associated with multiple negative health outcomes. Although Chinese people is one of the fastest growing populations in the world, there is a limited understanding of the epidemiology of physical function impairment in the global Chinese aging population.
 
Methods: Researchers used the PRISMA statement and performed a comprehensive online search to highlight the global epidemiology of physical function impairment of Chinese older adults in terms of prevalence, incidence, risk and protective factors, and health consequences. Search items include Chinese, older adult, Asian elderly, aging, physical function, physical function impairment, disability, function impairment, functional dependence, functional limitation, mobility, ADL, IADL, Nagi, and Rosow-Breslau.
 
Results: Eighty-two papers met inclusion criteria. Prevalence of ADL impairment ranges from 3.0% to 11.6%, while prevalence of IADL impairment ranges from 7.9% to 50.2%. Common risk factors include older age, female gender, lower education, lower income, rural residences, unmarried status, chronic diseases, depression/depressive symptoms, cognitive impairment, and falls. Health outcomes include suicidal ideation/attempted suicide, depression/depressive symptoms, cognitive impairment, falls, and mortality.
 
Conclusion: The prevalence of physical function impairment among Chinese aging population varies across regions and the number of physical function impairments increases over time. Physical function is influenced by multiple aspects, including socio-demographic characteristics, health conditions, and health behaviors, and can lead to adverse health outcomes. Future longitudinal research is necessary to explore the regional differences, effectiveness of existing intervention programs, as well as the cultural contexts of physical function impairment. Concerted support from caregivers, healthcare and social service providers, and policy makers is necessary to improve physical function and promote healthy aging among Chinese older adults.

Keywords

Physical function; Older adults; Chinese

Introduction

Physical function is an important indicator of an older adult’s current health status. Subsequent impairment, often referred to as physical disability, mobility disability, or functional limitation [1], may bring growing healthcare, social, and economic burdens to society, especially as physical function may decline as people age [2]. Increased life expectancy further implies higher risk of physical function impairment [3-6]. Additionally, impairment in physical health among older adults has been linked to comorbidities [7,8], incident falls [9], pain [10], and mental disorder [11,12], which could further compromise older adults’ quality of life and even be predictive of mortality [13,14], and may also raise concerns of caregiving burden [15], living environmental hazard [16-18], social engagement [19], and social circumstances [20,21].
 
Understanding physical function in Chinese older adults is important. According to the 6th Chinese National Population Census in 2010, the proportion of Chinese older adults aged 60 and above within the general population has increased from 8.0% to 13.3% within 20 years [22] and is projected to reach 19.3% by 2025 [23]. By 2050, it is estimated that 25% of the world’s aging population will beChinese [24]. As one of the fastest growing aging populations in the world [23], the Chinese older adult population may experience a great risk of physical function impairment, which is a serious social and public health concern. However, while many studies have been done in western countries to examine physical function among older adults, little is known in the Chinese aging population, especially among overseas Chinese population. Integrating existing information about physical function impairment among different Chinese communities can help to provide population estimates for the older adults in China and globally, as well as to direct future study and policy making.
 
The possible differences and similarities of physical function impairment between Chinese aging population and other racial groups warrant attention. Cultural differences may shape the understanding of disease prevention, health maintaining, and treatment [25]. In addition, genetic factors, life style, health care disparities may also partially contribute to the varied health status across different racial groups [26,27]. There is growing evidence reported that U.S. immigrants have poorer physical function compared to their US born counterparts [28]. Research has indicated worse physical health among Asian Americans compared to non-Hispanic white, and Chinese subgroup has the highest rate of prevalence of limitedphysical function compared to other Asian subgroups [29]. Chinese immigrant aging population may face a higher risk of poor health status due to cultural and linguistic barriers, social isolation, healthcare disparities, and acculturation [27]. Evidence has also suggested that relocation and loss of native support network might lead to health disparities among Chinese population [30-34]; the distress of being old combined with immigration-related barriers may make Chinese immigrant aging population even more vulnerable [35]. Furthermore, Chinese aging population may be impacted by barriers of access to health care including language, help-seeking behaviors, and traditional Chinese thinking [25,36], which may lead to delayed care and treatment, and increase the likelihood of having hysical function impairment.
 
Although risk/protective factors and health consequences of physical function impairment in general aging population has been identified in prior studies [9,13,19,37-48], the situation may differamong Chinese older adults due to a variety of socioeconomics, culture beliefs, health literacy, available social services, and access to healthcare resources [49]. Additionally, given the unique cultural characteristics of Chinese population, older adults may expect more care and support from family members, known as “filial piety” [50], especially for those have difficulty in daily task performance. Prior research suggested that a higher level of filial piety is associated with better self-rated health for older adults [51]. However, providingcaregiving is likely challenging for immigrant adult children due to cultural and linguistic barriers. Furthermore, Chinese older adults who suffer physical function impairment may face potential elderabuse and discrimination from others [20,52]; additionally, poor health or disability can be especially stigmatized in Chinese culture [21]. These cultural components play important roles which may mediate the relationships between physical function impairment, its risk/protective factors, and health outcomes. Moreover, looking at physical and functional impairment among Chinese aging population across countries and geographic areas can help us understand differences and similarities between populations and provide more comprehensive and better focused recommendations for health promotion. Last, understanding the epidemiology of physical function among Chinese older adults may effectively direct the allocations and uses of limited health care and social-care resources, as well as the development of future strategy at both macro and micro levels.
 
Despite the increasing awareness on physical function impairment among older adults, there has not been a systematic review of physical function impairment in global Chinese aging population. The purpose of this review is to improve our understanding of the epidemiology of physical function impairment among the global Chinese population including its prevalence, incidence, risk and protective factors, and health consequences, and also aims to collect evidence and extract information for directions for future research and health policy.

Materials and Methods

By using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, this review includes articles that discuss physical function problems among Chinese older adults globally. Inclusion criteria for this review paper are studies that report prevalence or incidences of physical function impairment, as well as risk factors, and health outcomes. Eligible studies focus on older adults aged 50 years old or above who self-identify as ethnic Chinese. The global literature was searched in the databases PubMed, MEDLINE, PsychInfo, China Knowledge Resource Integrated Database, and Wan Fang Data. Search keywords include: “Chinese”, “older adult”, “Asian elderly”, “aging”, “physical function”, “physical function impairment”, “disability”, “function impairment”, “functional dependence”, “functional limitation”, “mobility”, “ADL”, “IADL”, “Nagi”, and “Rosow-Breslau”. One review also identified and examined for relevant articles [38]. To refine our review, full manuscripts were further screened to eliminate ineligible articles. Exclusion criteria were: abstracts or case reports, qualitative studies, published over 25 years ago, written in non-English language, combined sample of Chinese and other race group, did not clearly define physical function as the primary dependent or independent variable, and examine the aggregate of physical function and other factors (Figure 1).
JCID-2373-1044-04-0016-thumbfig1
Figure 1: Flowchart describing review process for identification of eligible studies.
 

Results

There are a total of 125 articles identified through the online database search, and 82 of them met inclusion criteria. These 82 articles discussed physical function problems among Chinese older adults in Mainland China (n=35), Hong Kong (n=22), Taiwan (n=16), Singapore (n=2), and North America (n=7). Three papers have cross-city samples. Among eligible articles, 23 included the information regarding prevalence of physical function impairment, 5 reported the incidence of physical function decline and trends in physical function, 47 examined the risk and protective factors associated with physical function impairment, and 25 evaluated the health consequence related to physical function impairment. Author, year, study design, population and setting, key independent variables, covariates, outcomes and key findings are presented in Tables 1-4.
 
Prevalence
 
Prevalence of older adults’ physical function impairment varies across different Chinese communities depending on the setting, research methods, and measurements. Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL) limitations are most commonly measurements used to assess one’s physical function. The majority of studies used “difficulty in completing at least one item of daily tasks” as the cut-off point of ADL or IADL impairment [53-55]. The rates of ADL impairment ranged from 3.0% to 11.6% among global Chinese communities [23,29,56-64], while the rates of IADL impairment ranged from 7.9% to 50.2% (Table 1) [23,29,56,57,61]. Further, the prevalence of physical function impairment was relatively higher among Chinese population compared to other ethnic or racial groups. For example, the National Health Interview Survey of 738 Asian American older adults suggested that the Chinese subgroup experienced the highest ADL or IADL disabilities (11.6% ADL vs. 17.3% IADL impairment) compared to other subgroups of Asian Americans (Filipino: 8.3% ADL vs. 15.3% IADL impairment; Asian Indian: 4.6% ADL vs. 9.1% IADL impairment) [29]. Additionally, studies also report that Chinese older adults living in Chicago had a higher prevalence of IADL impairment in comparison with other Chinese older adults in Mainland China [23,56,61].
JGPC-2373-1133-04-0016-thumbtab1
Table 1: Prevalence of physical function impairment in Chinese aging population.
 In addition to ADL and IADL measurements, researchers have used other assessment tools to evaluate Chinese older adults’ physical function, such as Nagi index of basic physical activities and Rosow and Breslau index of mobility [56,65]. A recent paper documented that the rate of self-reported mobility disability was 8.9% in males and 8.5% in females among 616 community-dwelling older adults aged 60 or above in Chengdu and Suining [58], while another paper reported that the rate of low skeletal muscle mass was 9.55% in males compared to 6.63% in females based on a survey of 432 older adults aged 65 or above in Yanqing [66].
 
Incidence
 
Most papers reported that an increasing proportion of older adults experience physical function impairment over time (Table 2) [61,67-70]. For instance, the Chinese Longitudinal Healthy Longevity Survey, a four-year follow-up study of 11,112 older adults acrossChina, reported that the rate of ADL disability onset was 9.67% [67]. Additionally, these trends may differ by gender. A communitydwelling study conducted in Beijing reported that the ADL disability increased by 0.96% per year for males over a 15 years follow-up, while declining by 1.15% per year for females [70].
JGPC-2373-1133-04-0016-thumbtab2
Table 2: Incidence of physical function impairment in Chinese aging population.
 

Risk and Protective Factors

Social demographic factors
 
In terms of demographic factors, older age, female gender, lower socioeconomic status, and lower education levels are common risk factors of physical function impairment among Chinese older adults (Table 3) [23,29,54,56,60,61,64,65,71-84]. Previous research among Chinese older adults documented that older age was significantly associated with higher risk of physical function impairment [23,29,56,60,65,71,77,78,80-83]. Interestingly, a study of 7,845 Chinese older adults found that young-old older adults (60-69 years old) experienced higher severity of ADL impairment compared to an older subgroup (70 years old and above) [54]. Additionally, gender is another widely discussed predictor of physical function impairment; multiple studies indicated females are more likely to suffer physical disability or other ADL/IADL difficulties than males [29,54,56,65,71-75,82,84]. Further, two studies reported that older adults with lower socio-economic status or lower income have a higher proportion ofworsening functional status [61,80], while another study concluded that absolute income is not an important predictor of functionaldependency [85]. Moreover, higher self-rated financial adequacy wasreported to indicate better physical health [84]. With respect to the level of education, Chinese older adults with lower education levels were correlated with higher possibility of ADL and IADL impairment, or mobility decline [56,60,61,65,81,83]. One study further indicated that an individual with a lower education level was more likely to have early-onset functional limitation [82].
JGPC-2373-1133-04-0016-thumbtab3
Table 3: Risk and protective factors associated with physical function impairment in Chinese aging population.
 Regarding family arrangement, risk factors of physical function impairment include being unmarried or widowed, having fewer household members, and having more children [23,29,56,83]. While most studies reported that being unmarried or widowed can predict physical function impairment [23,29,56], one study found that married individuals in Beijing showed higher levels of ADL limitations compared to unmarried ones [65]. A research based on the data generated from 3,159 Chinese older adults in the Greater Chicago Area mentioned that having fewer household members and more children has been linked with ADL or IADL impairment [56].
 
With respect to location and immigration status, risk factors include living in a rural area, larger Chinese community, and living in the U.S. for more years [23,54,56,71,78,84]. Three studies from Mainland China indicated the difference of functional disabilities between rural and urban residents [23,54,78]. Compared with respondents living in urban areas, older adults living in rural areas had higher disability rates for all age groups [23,54]. One study found that rural residence was associated with ADL limitation among female participants [78]. In contrast, a study indicated that living in a rural area could lead to a less rapid increase in ADL difficulties [71]. Additionally, one study among 2,272 Chinese Canadian population reported that residing in communities with a smaller Chinese population was associated with better physical health [84]. In terms of immigration status, results based on a community-dwelling population of U.S. Chinese older adults indicated that having been in the United States and living in the community longer were associated with ADL or IADL impairment [56].
 
Health conditions
 
In terms of health conditions, disease, especially chronic conditions, is a major risk factor associated with physical function impairment. Relatedly, polypharmacy is another risk factor associated with physical function impairment [86]. Most commonly reported diseases include obesity [55,58,87], sarcopenia [77,88,89], stroke [14,55,62,63,69], diabetes [14,62,63,69,90], arthritis [60], asthma [69], heart disease [14], hypertension [14], tracheitis [60], and emphysema (Table 3) [62,63]. Regarding obesity as an example, several studies have reported that older adults with obesity not only had generally worse physical function but also had a greater risk of ADL or IADL disability [55,58,87]. High values of BMI or waist circumference are also used to predict poor physical function performance [57,91]. Dynapenia or dynapenic-obesity were also positively associated with an increased risk of slow gait speed, mobility disability, or ADL or IADL limitations [58,87]. Moreover, worsened health over the lastyear was correlated with older Chinese Americans’ ADL or IADL impairment [56]. However, only one cross-city study conducted in Shanghai and Singapore reported that the number of chronic diseases was associated with ADL measured functional disability [64].
 
Changes in the psychological and psychiatric status also play a pivotal role in describing the occurrence of physical function impairment. Common risk factors include helplessness or depressive symptoms [85,92], a history of neurological disease [74], psychiatric or mood disease [74], Parkinson’s disease [62,63,69], dementia [62,63,69], and cognitive impairment [14,64,93,94]. For example, individuals who experience helplessness or depressive disorders were reported to have ADL limitations, IADL limitations, or other physical disability [85,92]. On the other hand, psychological resilience was regarded as an important protective factor that can fight against ADL disability [67].
 
Additionally, other risk factors related to health conditions include frailty [95], high waist circumference [57], pain [96], and poor sleep quality [97]. Last, results generated from a sample with 875 older adults born at the Peking Union Medical College Hospital of China form 1921 to 1941 showed that older maternal age at birth (35 or above) could make children at a higher risk of ADL limitation in older age [59].
 
Health behaviors
 
Existing studies conducted among Chinese communities showed a better physical function if engaged in more physical activities such as Tai Chi [98,99], habitual walking [75], or being non-smokers or quitting smoking (Table 3) [71]. For example, a study contains 39 older adults in Beijing reported that those who practiced Tai Chi has higher knee extensor strength compared to those who do not (p<0.013). Another study in Singapore indicated that older adults with self-reported higher levels of habitual walking are more likely to have better performance in peak oxygen consumption (VO2 max), one measure to examine one’s physical performance and fitness (p=0.007) [75].
 
Other factors
 
In addition to those common risk and protective factors list above, there are other factors associated with physical function impairment, such as falls [81,100,101], home environmental hazards [101], ethnicity [73], Chinese health beliefs [102], healthcare unit size [74], quality of life [56], and agricultural occupation (Table 3) [78].
 
According to our review, falls and home environmental hazards are common risk factors of physical function impairment among the aging population [81,100,101]. A study conducted among 1,419 community-dwelling Chinese older adults in Hong Kong revealed that an incident fall could lead to lower scores of the Barthel Index, the Total Mobility Score in Tinetti Balance and Gait Evaluation, IADL, and slower gait speed (p<0.001) [100]. Home environmental hazards can also put older adults at a high risk of falls or other physical injuries and therefore have a negative impact on their physical function. For lder adults, two common home hazards were lack of grab bars and no protections against slipping in the bathroom [101].
 
Auyeung et al. have reported community-dwelling Chinese older adults in Hong Kong have lower mean appendicular skeletal mass scores compared to black and white counterparts, suggesting ethnicity may be an important indicator and contributor to physical function differences [73]. Out of all the papers included in this review, there is only one study conducted in 2,272 Canadian Chinese population which quantified and analyzed Chinese culture, finding Chinese health beliefs are associated with physical health and IADL limitations [102].
 
Consequences
 
Physical function impairment has multiple serious consequences among Chinese older adults, such as depression or depressive symptoms [11,103-109], cognitive impairment [110-112], fear of falling [113], falls [114,115], sarcopenia [89], pre-diabetes and diabetes [116], low anthropometric indices [117], a risking risk of dependency [118], and institutionalization [118], attempted suicide or suicidal ideation [119-121], and mortality (Table 4) [14,118,122-124].
JGPC-2373-1133-04-0016-thumbtab4
Table 4: Consequences of physical function impairment in Chinese aging population
 In Mainland China, studies showed that physical function impairment was associated with depression or higher depressive symptoms, while better physical function was positively associated with psychological well-being [11,103-109]. In addition, a history of falls is one of the most recognizable risk factors of physical function impairment, and physical function impairment in turn can result in falls [114,115]. Poor ADL performance can also make older adults fear falling, which has been shown among Chinese older adults [113]. Furthermore, reduced walking speed and stride length ay be a predictor of older adults’ rising risk of dependency and institutionalization [118]. Suicide or suicidal ideation is another consequence associated with physical function impairment [119-121]. For example, a study conducted among 8,399 Chinese older adults aged 60 or above in Shanghai reported that IADL disabilities were associated with attempted suicide. The researchers also demonstrated that more IADL disabilities is related to an increase in suicide attempts [119]. Moreover, impairment in physical function can lead to severe consequences among Chinese aging population such as a higher risk of mortality [14,118,122-124].

Discussion

Physical function impairment is prevalent among the global Chinese population. Additionally, most studies reported an increasing number of physical function impairment over time among Chinese older adults. Common risk and protective factors of physical function impairment can be described into three main dimensions including socio-demographic characteristics, health conditions, and health behaviors. Impairments in physical function can lead to adverse health consequences, both physical and psychological. These findings indicate potential healthcare and caregiving issues for Chinese older adults with physical function impairment and have important implications for future research and policy.
 
Prevalence/Incidence: The prevalence of physical function impairment varies across different regional and cultural groups; however, there are limited studies comparing the prevalence rates between Chinese and other racial groups. Lack of a standardizedevaluation makes it difficult to compare prevalence rates across multiple study groups. According to our review, only two studies conducted in North America did the comparisons of physical function impairment among different racial groups. One reported that the Chinese subgroup has the highest ADL or IADL disability prevalence compared to other Asian Americans [29], while the other reported the Chinese subgroup has the lowest disability prevalence compared to other Asian Americans [125]. The results are contradictory and further research comparing prevalence across different racial groups is needed.
 
Another study conducted among U.S. Chinese older adults in the Greater Chicago Area reported a high IADL impairment prevalence of 50.2% [56], which indicates Chinese immigrants may have a higher risk of physical function impairment due to unique factors associated with immigration status, such as acculturation [49,126]. Linguistic and cultural barriers can result in poor access to and use of healthcare services [127,128] and negatively influence Asian immigrants on their physical and mental health [128,129], which may lead to a high prevalence of physical function impairment. Although most studies reported increasing numbers of physical function impairment over time, this trend is not uniformly present in all research. There are three articles which reported a decline of ADL or IADL disability among Chinese aging population [53,70,130]. For example, a 10-year study examining the trends of ADL and IADL disability in a cohort of Shanghai reported that older adults in 2003, 2005, and 2008 were less likely to be IADL disabled compared to those in 1998, but no significant changes were found in ADL [130]. More longitudinal studies are needed to explore the trends of physical function impairment among Chinese older adults over time.
 
Risk and protective factors: Due to the diversity of studies with respect to setting, population, and research methodologies, a variety of risk factors have been identified to be associated with physical function impairment among Chinese older adults. According to our review, the most common risk factors of physical function impairment in Chinese aging populations include older age, female gender, lower education levels, lower socioeconomic status, unmarried, having fewer household members, rural residents, chronic diseases, depression or depressive symptoms, cognitive impairment, and incident falls, which resonated with prior studies conducted in other geographic areas with non-Chinese individuals [19,86,131-136]. However, one longitudinal study reported an increasing disability trend over time experienced by male rather than female [70]. The association between female gender and physical function impairment deserves further exploration. Research has also established among other racial and ethnic groups that smoking, alcohol abuse, an unhealthy diet associated obesity, and lack of exercise could cause worsening in physical performance [81,133,134,137,138]; similarly, our review revealed that healthy lifestyle behaviors may lead to better physical functioning among Chinese older adults, such as engaged in more physical activities, practicing Tai Chi, habitual walking, and being non-smokers or quitting smoking. Notably, there is still limited knowledge regarding other factors like ethnic or racial differences. For example, although one prior study reported that Asian older adults may experience poorer physical function than other ethnic groups [73], but still, very little is known about the ethnic difference in physical function impairment between Chinese and other aging populations.
 
Consequences: Depression or depressive symptoms, cognitive impairment, fear of falling, falls, sarcopenia, attempted suicide or suicidal ideation, and mortality are established health consequences associated with physical function impairment for Chinese older adults. These findings were consistent with research conducted among other racial groups [9,13,39-48]. Notably, depression or depressive symptoms, falls, sarcopenia, and cognitive impairment were reported not only as risk factors but also as outcomes of physical function impairment. For example, falls may directly lead to physical function impairment, and also may confine older adults to homes and limit their activity due to fear of falls, which may further accelerate functional loss and put older adults at a higher risk of recurrent falls.
 
The relationship between these factors and physical impairment warrants further investigation among the Chinese aging population. Additionally, there are limited studies examining other health consequences associated with physical function impairment among Chinese aging population, which has been reported in other cohorts, such as self-neglect [139], and pre-diabetes or diabetes [116].
 
Previous studies have highlighted the impact of physical function impairment on the occurrence of mental health issues such as depression or depressive symptoms, and suicidal ideation among older adults [12,92,119-121]. Older adults with physical function impairment are experiencing difficulties in performing daily tasks or mobility, which indicates they may become more dependent and treat themselves as a burden to others. In particular, deeply influenced by Confucian culture, Chinese older adults may have high expectation of filial piety of the younger generation and rely on their children or other family members [50]. Thus, emotional support and caregiving from children or family members tend to be important for Chinese older adults, especially for those with physical function impairment. Unfortunately, the actual behaviors of children do not always fit the expectation of parents due to having difficulty of work-life balance, and disparities of culture values between East and West [50]. That could be one explanation why psychological issues are commonly reported among Chinese older adults [140-144], and why physical function impairment among Chinese older adults is linked to depressive symptoms or suicidal ideation.
 
Overall, there are several limitations in the current research field of physical function concerning Chinese older adults. First, there is a lack of a standardized evaluation to measure one’s physical function. Older adults’ physical function is usually measured by self-reported evaluation or observed performance-based tests. For physical and mobility disability assessments, Activities of Daily Living (ADL), Instrumental Activities of Daily Living Scale (IADL), the Barthel Index, and the Health Assessment Questionnaire (HAQ) Disability Scale are most commonly used. For functional assessment tools, Tinetti Performance Oriented Mobility Assessment Tool, Walking Speed, Functional Independence Measure, and Timed Up and Go (TUG) test are considered [145-147]. A variety of instruments are used in different studies in order to meet different research needs. However, this also decreases the ability to compare across studies. Even for studies that use same measurement, cutoff points that define impairment may differ, leading to vast variations in estimating the prevalence of physical function impairment. Researchers should expand efforts to develop a more-consistent instrument and standardized cutoff points for future assessment of physical function impairment to facilitate comparisons across studies. Another limitation is the discordance between self-reported and performance based tests in previous research [56]. For self-report tests, Chinese older adults may be reluctant to report true situation about their physical function status due to the traditional Chinese value of “saving face”. As a result, the accuracy and credibility of results could be reduced. Additionally, the sample sizes of most existing studies among Chinese older adults are relatively small. A large and representative sample size is encouraged to provide more convincing evidence for future strategy planning and policy making in health promotion. In terms of the limitations of this review, we did not include peer-reviewed manuscripts in non-English languages Nevertheless, this systematic review characterizes the state-of-science in physical function, reveals physical function impairment is an important issue among global Chinese aging population, as well as illustrates the future research direction and practical strategies.

Future Research Directions

Knowledge gap: While it has been shown that many medical conditions are associated with increased risk of physical function impairment among Chinese older adults [148], there are a few particular areas which have yet to be adequately explored. First, there is a lack of research that addresses the association between comorbidity and physical function impairment among Chinese aging group, which has been shown in a Canadian community and an American community [7,8]. Additionally, visual impairments but not hearing impairments were reported to be a risk factor of future ADL disability [149], but little is known about these associations among Chinese aging population. Larger healthcare facilities may have more health and human recourses that can provide older adults satisfactory care and support, decreasing the risk of experiencing physical limitations, but there are many unknown confounding factors between healthcare unit size and older adults’ physical status, and more studies are still needed to further demonstrate this association. Furthermore, research has focused on the risk factors of physical function impairment, while inadequately addressing its protective factors.
 
Similarly, there are several consequences of physical function impairment that has been widely reported in other race groups, but are not yet fully examined among Chinese older adults, especially in overseas Chinese aging population, such as increased risk of mortality [13,48], attempted suicide or suicidal ideation [150,151], and depression or depressive symptoms [152,153]. As one of the most severe outcomes of physical function change, more attention should be paid to the relationship between mortality and physical function impairment. Additionally, attempted suicide or suicidal ideation may further result in higher risk of mortality, suggesting the importance of offering psychological counseling service to prevent suicide or suicidal ideation for those vulnerable groups. More studies are still needed to evaluate the associations between depression and depressive symptoms or other mental disorders and older adults’ physical function impairment, as well as examine how mental health care can prevent Chinese older adults with physical function impairment from developing severe psychological illnesses.
 
Moreover, for overseas Chinese older adults, there is limited information generated from communities or institutes in Singapore, Canada, and the United States. Since an increasing number of Chinese immigrants are living in different foreign countries, and overseas population might have different experience in physical function impairment than Chinese population in China due to diversity of socioeconomics, acculturation levels, citizenship and immigration status, culture beliefs, language, and access to healthcare services [154-156], a lack of representative studies in other regions may impede to develop a comprehensive understanding on this aging issue. More studies conducted in overseas Chinese communities, as well as more comparative data across different regions and cultural groups are needed.
 
To advance our understanding of trends in physical function change in Chinese aging population over time, longitudinal studies are needed among the aging population living in the Mainland China as well as overseas Chinese communities. Despite quantitative analysis, qualitative studies can help to generate an in-depth understanding of the concerns, needs, and barriers of older adults with physical function impairment as well as the cultural context behind this aging issue. It is also important to better provide social and healthcare services for older adults and to develop effective intervention programs.
 
Cultural components among Chinese aging population: First, existing studies did not fully consider the potential influence caused by filial piety or caregiving and how it relates to poor physical performance in Chinese population. Considering the culture components could be critical for better research and intervention design to address potential biases when understanding physical function in a Chinese population. Second, one study conducted in Chicago reported that a decline in physical function was related to higher risk of elder abuse [20], while other studies indicated thatthere was no significant association between physical dependence and a greater risk of elder abuse [157,158]. Given that elder abuse is a serious and common public health concern among Chinese older adults [158], older adults may face burden of grand-parenting [159], and there is a lack of evidence-based research conducted in diversity Chinese communities, it is important to explore the complexity of the relationship between physical function impairment and elder abuse. Third, the ethnic difference of physical function impairment between Chinese older adults and other racial groups has been shown in someprevious studies [29,56,125]. More studies are still needed to explore these across racial groups by considering disparities in life styles, eating habits, geographic settings, socio-economic characteristics, and cultural values. Further, there is diversity within Chinese aging population, which has yet to be explored.
 

Implications for Practical Strategies

There are implications for practical strategies from individual, familial, and policy levels. First, “self-improvement” is important to promote healthy aging and prevent physical function impairment among Chinese older adults [160]. Given the evidence regarding possible intervention strategies, moderate physical activities and partnerships with trained medical professionals may be helpful to maintain physical health for Chinese older adults. Our review findings also suggest that mental health were related to older adults’ physical function status. Intervention strategies which emphasize physical, psychological and social wellbeing, either through clinical trials or social services, should consider linguistically and culturally appropriate measures to better serve diverse aging population. Given the diversity of physical function in older adults’ socio-demographic characteristics, risk and protective factors, and health status, the intervention programs design and health policy making should especially focus on these high-risk groups. Cost effectiveness and applicability of new developed intervention programs should also be considered. Additionally, policy makers should invest in more resources for all individuals, families, and systems involved in caring for Chinese older adults based on the concerning prevalence rates of physical impairment globally. Caring for impaired older adults may be a traditional Chinese value; however, especially for overseas Chinese communities, Chinese adult children may experience a disproportionate burden due to lack of linguistically and culturally appropriate support. Future efforts should expand to promote the collaboration between research institutions and community organizations to better address these concerns and needs [161].
 
Furthermore, safe living environments for older adults are important for Chinese older adults with physical impairments. As people age, falls are more frequent and serious due to poor balance function, weak muscle strength, and thinning of bones [136]. The home environmental hazards should be removed to prevent incidence falls or injuries. Legislation can be an effective safeguard of rights of older adults with physical function impairment. In 1990, the U.S. Congress enacted the Americans with Disabilities Act (ADA)to prevent disabilities from discrimination, to defend their rights, and to take care of them regarding employment, public entities and transportation, public accommodations and commercial facilities, and telecommunications. China also promulgated the Law of the People’s Republic of China on the Protection of Disabled Persons in 1990 to protect disabilities on aspects ranging from rehabilitation, education, employment, cultural life, welfare, environment, to legal liabilities [162]. While these legislations have promoted health equity for older adults, special attention should be paid to the accessibility of these resources for individuals who have limited English proficiency and may experience other cultural or structural barriers in accessing services. Although this multifaceted approach across individual,familial, and structural level may be difficult, joint efforts and close collaborations of the whole society are necessary to facilitate better health and quality of life among older adults, their families, as well as the general population.

Conclusion

Developing of physical function impairment is a natural process as people age. This review highlights physical function impairment; its risk and protective factors, and associated health consequences to advance the understanding of this complicated aging issue among the global Chinese population. Global longitudinal studies are critical to examine the regional and ethnic differences, effectiveness of existing intervention programs, and how physical function impairment relates to culture components such as filial piety and elder abuse. In addition, the relatively high prevalence and a growing number of physical function impairment over time in Chinese aging population reveal the importance of enhancing older adults’ physical fitness and call for more physical function screenings, long-term healthcare and service services, health policy support, and multifactor intervention programs for Chinese older adults. Also, the effectiveness, feasibility, and sustainability of existing interventions should be evaluated.

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