Background

The term disability was first defined by Nagi in the 1960s [1]. The World Health Organization (WHO) has developed an updated framework [2] in 2002, which considers the term as an umbrella term for impairments, activity limitations and participation restrictions, and emphasizes that disability is a long-term interaction between the person and the overall environment in which the person lives. This implies that disability is a complex and multifactorial state involving multiple risk factors. Currently, there are no uniform standards and methods for assessing and classifying disability in older adults. In order to obtain comparable global health data, various tools for measuring disability have been developed [3,4,5,6,7]. The most commonly used one is the Barthel Index (BI) [8], which can evaluate the ability of older adults to perform daily living activities. It is characterized by its simplicity of operation, good reliability and sensitivity [9].

Human life expectancy has reached an all-time high and is on the rise [10], which will lead to the emergence of a large number of older adults with different degrees of disability [11]. Disability not only affects the quality of life and health outcomes of those people, but also significantly increases the cost of care [12]. Collecting data from representative studies in 37 countries, WHO reports that 14% of the 514 million older people (60 years and older) lack the basic skills to lead a meaningful and dignified life [10]. By the end of 2015, China's elderly population had reached 40.63 million, accounting for 18.3% of older adults in the same period [13]. It is conceivable that China, as the largest develo** country globally, is facing a great socioeconomic burden.

Previous studies have explored a range of factors that may affect the physical functioning, activity, and social participation of older adults, including but not limited to sociodemographic characteristics, social networks, self-perceived health, cognitive functioning, mental health, disease burden, and repeat hospitalizations [14,15,16,17,18]. Since 2005, many similar studies have been conducted in most regions of China, but few studies have been conducted in the Southwest [19,20,50]. However, follow-up cohort studies are still needed to elucidate the specific trajectory of disability. Aging poses a number of psychiatric problems in older adults that are caused by many factors, including: 1) decreased sensory function [51]; 2) decreased adaptability to environmental changes and social roles and status; and 3) increased likelihood of exposure to negative life events, such as retirement and death of a relative. In this study, 8.2% of the elderly screened positive for mental disorders, and the rates of positive depression and anxiety-depression comorbidity were significantly higher in the disabled elderly. In addition, less interaction with family and friends increased the incidence of disability. However, alienation from family alone did not have a statistically significant effect on disability, which may be related to the current situation of empty nesters in China. Older adults rely more on interactions with friends than the next generation who are busy with work. According to the meta-analysis, the prevalence of depression among Chinese empty nesters was 38.6% [54]; while, these hospitals do not provide community mental health services that can provide long-term care and support. As early as 2004, China attempted to establish a comprehensive community mental health system; however, the system continues to face significant challenges due to low national awareness of the need for mental health services, lack of specialized physicians, and financial difficulties [55]. This study will provide a reference for regional epidemiological data on mental disorders in the elderly, and also call for relevant authorities to pay attention to the mental health problems of the elderly.

Consistent with previous studies [56], our findings suggest a strong association between cognitive function and disability. The survey showed that 1,179 elderly people had positive dementia screening results, and the proportion of dementia in the disabled population was 4.8 times higher than that in the non-disabled population, which fully indicates that dementia is an important cause of loss of self-care in the elderly. As the country with the largest number of dementia patients in the world [57], China has not yet established a service system specifically for dementia. Early detection of cognitive impairment is not possible due to low public awareness of dementia and the lack of routine screening mechanisms in most medical facilities. Many people with dementia rely on home care, which is increasingly being incorporated into long-term care. However, the lack of caregivers with spiritual and professional background makes it difficult to improve the quality of life of these elderly [58]. Therefore, the following steps should focus on increasing public awareness of dementia, earlier identification and prevention of cognitive impairment, and the establishment of a joint disability service system for dementia.

Statistically significant differences in disability were observed between genders, and the older women were more prone to experience functional impairment. However, after adjusting for other variables, the incidence of disability became similar between genders following adjustment of other variables, which might be explained by higher rates of chronic diseases such as osteoarthritis, dementia, falls, and mental disorder in women [59], as well as differences in body composition and life expectancy gaps [60]. For social factors, the analysis showed that older adults who live in urban areas and have formal education are better able to maintain their abilities, as has been well documented in many studies. This may be because they have access to health knowledge and resources from a variety of sources [61] as well as a range of social and recreational activities, which can help them maintain good mental health [62]. Despite China's increasing spending on healthcare and health, inefficiencies and uneven distribution of resources persist. Because of the differences in economics, healthcare, urbanization, and population density between the east and west, it is difficult to see a boom in care services and elderly care in the rural west anytime soon [63]. This study will offer policy implications and help local elder population to improve the quality of life.

This study has several strengths. First, this large sample study can provide high-quality and rich information for existing disability research, and the findings are important for follow-up studies and the global literature on the disability process and its associated factors. Second, comprehensive training of professional bodies and various quality control measures yielded reliable data. Finally, the study results provide a scientific basis for government policies and resource allocation to enable local older adults to have a higher quality of life and gradually achieve healthy aging. Several limitations should be taken into account when interpreting this study. As this study is a cross-sectional study, the results failed to determine a causal relationship between influencing factors and disability. Therefore, although many factors influencing disability were identified in this study, it cannot be denied that disability may also influence related factors to some extent. Further cohort studies are needed to determine the causal relationships. Some of the data on health characteristics and ADL items were self-reported, and biases in recall and reporting may have affected the information. Future studies should add more objective indicators and try to assess disability in multiple dimensions, rather than just selecting ADL as the only criterion for determining disability. This study served as a baseline investigation for our project, and more follow-up and exploration of interventions are needed in the future.

Conclusions

A higher prevalence of disability was found among urban and rural older adults in Sichuan, where disability was strongly associated with aging, lower education levels, living in rural areas, hospitalization, co-morbidities, self-rated poor health, falls, cognitive impairment, psychological problems, and changes in social networks. The findings underscore the need for early screening for disability, effective prevention policies, smaller urban–rural disparities, and age-friendly society.