Disability encompasses a spectrum of conditions, from impairments to activity limitations and participation restrictions, reflecting the complex interplay between an individual’s health and their environmental and personal context (1). This phenomenon not only impacts the quality of life for the older adults but also presents significant challenges for society, including increased healthcare costs and the need for comprehensive support systems. Additionally, it is associated with elevated mortality risks, particularly for those with chronic conditions (2). The severity of disability is directly linked to reduced life expectancy, Active Life Expectancy (ALE), Disability-Free Life Expectancy (DFLE), and an extended period of living with a disability (3). Moreover, as disability levels rise, so does the annual medical insurance expenditure, highlighting the economic implications of this health concern.

According to the seventh national population census, China has 190 million individuals 65 years of age and older, representing 13.5% of the total population. As a major city in southern China, Guangzhou also has more than 1.4 million people within this age range, accounting for 7.82% of its population. Consequently, the increasing incidence of disability among older people has become a growing concern. Estimates suggest that 26.2% of older persons in China live with disability (4), making it a critical public health challenge. The urgency of developing comprehensive strategies for prevention and rehabilitation is paramount.

There is a growing body of evidence that links inflammation to an increased risk of disability. Elevated levels of inflammatory cytokines can disrupt muscle protein synthesis, reduce muscle cell generation, and accelerate muscle breakdown, ultimately leading to reduced muscle mass and strength (5–7). This, in turn, affects daily functional capacity. Additionally, high inflammation levels are associated with vascular diseases and other age-related conditions, such as cardiovascular and cerebrovascular diseases (8), exacerbating the progression of disability among older people. The onset of disability itself can further increase inflammation, creating a detrimental feedback loop.

Diet is a modifiable factor that significantly influences inflammation levels. Unhealthy diets, particularly those high in red meat and dairy, are linked to increased inflammation, while whole grains have been shown to possess anti-inflammatory properties (9, 10). The “dietary inflammatory index” (DII) is a valuable tool developed by researchers to measure the inflammatory potential of an individual’s diet (11). This index considers both pro- and anti-inflammatory effects of various foods and nutrients, offering a potential pathway to healthier dietary choices that could mitigate inflammation and prevent disability.

Previous studies have explored the relationship between the DII and functional limitations in older adults. For instance, Wang et al. found that higher DII scores were associated with increased odds of functional limitations in overweight and obese individuals in the United States (12). Similar associations have been observed in older Japanese individuals (13) and in a Spanish cohort (14). However, there is a dearth of research focusing on the older population in China, and the specific impact of DII on the degree of disability in this demographic remains unclear. Furthermore, existing studies have not fully explored the influence of other relevant factors on the progression of disability within the older adult population.

Our primary aim is to evaluate the factors associated with the degree of disability among older adults and to investigate the potential link between the DII and the degree of disability in southern China. This research seeks to fill a critical gap in the literature and contribute to the development of tailored interventions for this at-risk population.

In this cross-sectional investigation carried out in Guangzhou, China, we enrolled 262 participants to examine the correlation between the Dietary Inflammatory Index (DII) and the prevalence of disability among older population. Our principal findings are as follows: participants with severe disability exhibited a notably higher mean DII score compared to those with mild to moderate impairments. Factors such as physical activity, stroke, and dementia were found to be linked to disability, with a significant association observed between an increase in DII scores and the extent of disability, even after adjusting for confounding variables.

Our research indicates a correlation between the level of physical exercise and the degree of impairment in the older people. Specifically, we found that individuals who have never engaged in physical activity were 8.48 times more likely to experience severe disability, compared to those who maintain an active lifestyle. Despite the fact that many older adults with severe disabilities were precluded from exercise due to physical constraints, our data suggests that a history of physical activity correlates with a reduced risk of exacerbated disability. This aligns with the findings of several findings, highlighting that exercise habits adopted early in life, such as in midlife, can exert long-lasting effects on disability outcomes in later years (18–20). As a pivotal strategy recognized for mitigating physical decline among older population, regular physical activity can decrease the incidence of chronic diseases, diminish age-related oxidative stress and inflammation, enhance autophagy and mitochondrial function, and improve muscle quality, insulin-like growth factor-1 (IGF-1) signaling, and insulin sensitivity (21, 22). A multicenter randomized trial emphasizing mobility disability reduction through exercise demonstrated that older adults with physical disabilities who participated in a structured moderate-intensity activity program exhibited a more pronounced reduction in the risk of mobility disability and mortality than those who attended health education sessions (23). Furthermore, a meta-analysis suggests that individuals with disabilities can derive health benefits from less than 150 min of physical activity per week, indicating that some level of activity is preferable to none (24). However, active exercise may not be practicable for all, especially those with severe disabilities. Our study revealed that only a negligible 0.8% (1 out of 125) of individuals with severe disability were engaged in regular physical exercise. Nonetheless, passive exercise, including simple activities like passive finger movements presents a feasible alternative (25, 26). In light of our findings and existing research, it is imperative that physical activity be integrated into the rehabilitation of older adults with disabilities to delay or even reverse the disablement process.

Stroke and dementia are critical determinants influencing disability in older people (27). With over two million new cases annually, stroke has emerged as a leading cause of death and disability in China (28). The Chinese Longitudinal Healthy Longevity Survey (CLHLS) indicated that the prevalence and severity of activity limitation among older stroke survivors in China were several-fold higher than among those with non-stroke chronic conditions, particularly among older individuals aged 80 and above, as well as those who had not received formal education (29). This discrepancy may be attributed to cerebral infarction-induced hypoxia and ischemia, resulting in brain cell damage or death, and leading to issues such as limb weakness, speech disorders, and cognitive decline (30, 31). The risk of post-stroke hemiplegia is notably high, contributing to a higher degree of disability (32). Stroke and dementia share common risk factors (33), cognitive impairment and dementia frequently subsequent to a stroke (34, 35). A trajectory modeling study found that individuals with probable dementia, alone or in conjunction with complicated self-care conditions, had significantly increased odds of following a “severe disability” trajectory. Dementia may compound self-care challenges, while effective self-care may decrease preventable hospitalizations and thereby reduce disability associated with activities of daily living (ADL) (36). Furthermore, Vargese et al. identified a robust correlation between dementia and ADL and mobility disability (37). Given the essentially irreversible progression of dementia, the disparity in disability between individuals with and without dementia widened over a 17-year follow-up period, with more significant functional improvement observed in those without dementia. Thus, irrespective of other chronic diseases, individuals with dementia are more likely to experience a more profound degree of disability with limited prospects for amelioration.

Our study uncovered a positive correlation between the Dietary Inflammatory Index (DII) and the severity of disability among older people, aligning with previous research findings. Masuda et al. observed in Japanese older population that an increase in DII score was linked to a heightened risk of overall disability, as well as disability in instrumental activities of daily living, intellectual activities, and social participation (13). Our focused regression analysis on comprehensive disability revealed that individuals with more severe disability consistently exhibited lower ability scores across all three dimensions, with these differences reaching statistical significance. Similarly, Wang et al.’s cross-sectional study in the United States found that, compared to the lowest DII quartile, higher quartiles were associated with an increased risk of functional disability, although this did not extend to ADL disability (12). The discrepancy may be attributed to the differing disability assessment criteria used; their study’s narrower definition of disability, which excluded partially dependent responses, led to an underestimation of actual ADL disability. Additionally, both our study and Wang et al.’s found no nonlinear relationship between the DII and disability through RCS curve analysis.

An elevated DII may exacerbate disability in older adults by impacting physical activity and cognitive abilities. A diet high in pro-inflammatory compounds can induce systemic low-grade chronic inflammation, which increases the risk of muscle atrophy and accelerates the loss of muscle strength and mass, particularly in the lower limbs (6, 7, 38). This can lead to reduced mobility, such as difficulty with stairs or walking, which in turn decreases physical activity, appetite, and digestion, ultimately resulting in reduced food intake (39). Our study showed that as the degree of disability in older people increases, their intake of essential nutrients like energy and protein declines, which are vital for preventing and managing sarcopenia (40). Thus, there may be a bidirectional relationship between the chronic inflammation from a pro-inflammatory diet and the degree of disability among older adults. Furthermore, decreased muscle strength is a significant risk factor for falls in older adults (41), which can lead to fractures and further reduce mobility, as well as foster a fear of falling that diminishes self-confidence (42–44). Okoro et al. highlighted the significance of addressing barriers to healthcare and promoting health equity for all, particularly recognizing the additional challenges faced by individuals with disabilities in accessing appropriate medical care (45). Our study also found that many older adults, due to mobility issues and concerns about increasing caregiver burden, are hesitant to seek medical care, leading to delayed treatment and worsening disability (46). However, home-based medical services provided by family doctors, which include regular assessments and tailored medication adjustments, could alleviate some of these issues (47). Therefore, the promotion of such home-based services, particularly for older adults with disabilities, should be considered in future healthcare strategies.

Concurrently, the DII has been observed to significantly increase the risk of cognitive-related diseases, ranging from mild cognitive impairment to dementia (48, 49). As cognitive abilities decline, older adults may struggle to perform daily activities independently and manage their own illnesses, such as adhering to medication regimens, thereby increasing their reliance on caregivers (50). A randomized controlled study showed that cognitive function therapy can significantly reduce the degree of disability compared to exercise therapy (51). Consistent with our multivariate ordinal logistic regression findings, only individuals with a history of stroke or dementia showed an increased risk of disability, suggesting that maintaining cognitive function may be particularly important in reducing the risk of severe disability among older adults, compared to other physical functions. These findings highlight the complex interplay between diet-induced inflammation, physical decline, cognitive impairment, and disability among older people. Effective interventions targeting both physical and cognitive aspects are crucial to mitigating the progression of disability, emphasizing the importance of integrated healthcare approaches.

Given the significant role of diet in this interplay, addressing dietary factors that may influence the progression of disability is crucial. Based on the analyses of dietary intake, it is recommended that older individuals with severe disability opt for nutrient-dense foods such as whole grains, lean meats, and fish to meet their daily energy requirements. As needed, consider using nutritional supplements to ensure adequate energy intake (52). Additionally, it is encouraged to consume foods rich in anti-inflammatory nutrients like vitamin A, vitamin C, and magnesium, including fruits, vegetables, eggs, dairy products, and nuts (53). This dietary approach, which emphasizes the consumption of high-quality proteins and unsaturated fats, may enhance overall health and potentially mitigate the risk of inflammation, thereby slowing the progression of disability.

This study is not without its limitations. Firstly, as an observational cross-sectional study, it cannot establish causality and may be subject to reverse causation. For example, older adults with a higher degree of disability may face challenges in chewing, have poorer appetites, and encounter difficulties in food procurement, leading to an elevated DII. Secondly, the dietary survey’s reliance on a food frequency questionnaire (FFQ) to assess dietary intake over the past month introduces the potential for recall bias, although the tailored FFQ may have enhanced the precision of our findings. Thirdly, the absence of objective measures such as physical function and muscle strength limits a comprehensive understanding of disability among older adults. Additionally, despite controlling for 14 covariates, it is important to acknowledge that disability is a complex condition influenced by various environmental and personal factors, and thus potential confounding factors may still be present.

Despite these limitations, our study has several strengths compared to previous research. Firstly, it is the first to explore the association between disability and the DII in the Chinese older population. Secondly, our research uniquely focuses on the variations in the degree of disability among older individuals, offering valuable insights into how dietary inflammation may differentially impact those with varying levels of disability.

In synthesis, while our study does not provide definitive conclusions, it does uncover a positive correlation between the Dietary Inflammatory Index (DII) and the prevalence of disability among Chinese older people, highlighting several critical associated factors. It is recommended that older adults with disabilities aim to lower their DII levels by adopting anti-inflammatory dietary patterns and engage in personalized exercise and cognitive rehabilitation programs, especially those who have experienced stroke or dementia. Recognizing the constraints of a cross-sectional study design, it is imperative that additional research be conducted to confirm the causal relationship between the DII and disability among older adults and to clarify the biological mechanisms by which diet-related inflammation may contribute to disablement in later life.