This prospective nationwide study utilised a 4-node RCS curve and a COX regression model for the first time to evaluate the relationship between FI and PP-MM. This study identified 4,502 cases of pre-frailty and 854 cases of frailty. The COX regression model indicated a correlation between FI and PP-MM prevalence in middle-aged and older Chinese individuals. Moreover, pre-frail and frail participants exhibited a higher risk of PP-MM. The RCS findings revealed that the prevalence risk of PP-MM increased as FI increased, and the rate of increase was more rapid in the pre-frail period.
Positive associations between frailty and the risk of a single chronic condition have been studied, including heart failure, coronary artery disease(Ijaz et al., 2022), chronic obstructive pulmonary disease, and asthma(Qu et al., 2024). Several studies have also explored frailty and multimorbidity, demonstrating that frailty is strongly associated with chronic disease multimorbidity(Hanlon et al., 2018; Luo et al., 2023). This is consistent with our findings. A study discovered that depression partially mediated the association between prior frailty and subsequent multimorbidity(Feng et al., 2023), possibly because most frail patients have chronic inflammatory conditions, including elevated levels of interleukin-6, which is a significant risk factor for various chronic illnesses(Ferrucci and Fabbri, 2018). Frail older adults with multiple chronic diseases experience an accumulation of inflammatory conditions that may prolong the pro-inflammatory state, increase cortisol levels, and reduce muscle mass, physiological reserve, and immunocompetence, creating a vicious cycle(Chang et al., 2010). Frail older adults may experience disability or functional dependence, pain due to chronic conditions, activity limitations, and poor endurance, leading to depression and psychological problems(Woods et al., 2005). Therefore, we suggest incorporating frailty assessment into the routine monitoring and evaluation of patients with chronic conditions, leading to the identification of those at greater risk of PP-MM and facilitating targeted clinical care and health management.
A comprehensive longitudinal study on frailty transitions in community-dwelling adults revealed that over 50% of participants transitioned between frail states. Moreover, although most of these transitions were to more frail states, some made transitions to less frail states, suggesting that frailty is reversible(Gill et al., 2006) and can be reversed through interventions(Shi et al., 2021). This study determined that the HR and 95% CI for PP-MM were greater than 1 at FI of 0.10 and that the risk of developing PP-MM increased more rapidly as FI increased between 0.10 and 0.25 and slowed down after FI of 0.25. This revealed a significant relationship between the increase in FI and the risk of PP-MM prevalence in the pre-frail period. Moreover, the pre-frail period may present a better opportunity to implement interventions to prevent PP-MM, providing new evidence for PP-MM prevention.
In this study, we found that the HR and 95% CI for PP-MM were greater than 1 at FI of 0.10 and that the prevalence risk of PP-MM rose faster with increasing FI between 0.10 and 0.25 and slowed down after FI of 0.25. This suggests that the relationship between rising FI and PP-MM prevalence risk is meaningful in the pre-frail period and the pre-frail period may be a better opportunity to implement interventions for PP-MM prevention. This provides new evidence for preventing PP-MM.
This is the first time that the association between FI and PP-MM has been explored longitudinally using a large sample from a nationally representative sample. This study used the COX regression and RCS models to estimate the association between FI and PP-MM in middle-aged and older adults. A series of subgroup analyses and interactions were conducted to confirm the robustness of our results.
This study has several limitations. First, the respondents self-reported physical, psychological, and cognitive impairments, which may have introduced recall bias and neglected undiagnosed disorders. Second, despite adjusting for many potential confounders, the possibility of residual confounding factors could not be eliminated. Finally, although longitudinal studies have yielded stronger correlations between FI and PP-MM than cross-sectional studies, we remain unable to establish a causal relationship or elucidate the underlying biological mechanisms. Further experimental studies are required to confirm this association.