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. 2025 Jun 11;37(1):186.
doi: 10.1007/s40520-025-03091-8.

The distribution of the frailty index among different arthritis patients and the association between the frailty index and mortality in rheumatoid arthritis patients among U.S. adults (results from NHANES 1999-2018)

Shi-Chao Tang #  1 , Lei Jin #  2 , Yong-Qi Hu #  3 , Jun-Feng Peng  4 , Yan-Qing Wang  5 , Chong Shao  1 , Yu Liu  6
Affiliations

The distribution of the frailty index among different arthritis patients and the association between the frailty index and mortality in rheumatoid arthritis patients among U.S. adults (results from NHANES 1999-2018)

Shi-Chao Tang et al. Aging Clin Exp Res. .

Abstract

Background: We conducted to examine the prevalence of frailty among different arthritis populations and to elucidate the associations between frailty and all-cause and cause-specific mortality among rheumatoid arthritis (RA) in the American adults.

Method: National Health and Nutrition Examination Survey (NHANES) database spanning 1999 to 2018 was collected, supplemented with pertinent mortality records from the U.S. National Death Index (NDI) up to December 31, 2019. The Frailty Index defined by Searle was adopted. Different types of arthritis include: RA, Osteoarthritis (OA), Psoriatic Arthritis (PsA), and others. Statistical methods mainly included maximum selected rank statistics, univariate and multivariate COX regression models, and Restricted Cubic Spline (RCS).

Results: The frailty indices of different arthritis populations were 0.24, 0.21, 0.21, and 0.20, respectively. The cut-off value for the frailty index was 0.3. Compared to those with a lower frailty index, participants with a higher frailty index exhibited higher risks of all-cause mortality (HR = 2.11, 95% CI 1.70-2.62), heart disease mortality (HR = 2.38, 95% CI 1.53-3.70), lower respiratory disease mortality (HR = 3.79, 95% CI 1.62-8.88), and influenza and pneumonia mortality (HR = 6.08, 95% CI 2.12-17.42). Frailty-associated all-cause mortality risks increased with age among different age groups.

Conclusion: Frailty was particularly pronounced among RA patients. Relatively high frailty index could predict higher all-cause and cause-specific mortality among RA adults in America, and the all-cause mortality related to frailty increased with age. Frailty index could be utilized as a prognostic marker in RA management. Timely interventions are paramount for optimizing patient outcomes.

Keywords: Frailty index; Mortality risk; Nutrition Examination Survey database; Rheumatoid arthritis; Survival analysis.

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Conflict of interest statement

Declarations. Conflict of interest: The authors declare no competing interests. Human and animal rights: The NCHS research ethics review board approved the NHANES study protocol, and participants provided written informed consent at enrollment. The review board of Tongren Hospital, Shanghai Jiao Tong University School of Medicine determined the study to be exempt because it used publicly available de-identified data, and the patient had already signed informed consent upon enrollment. The present study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. Informed consent statement: None declared.

Figures

Fig. 1
Fig. 1
Flowchart of data extraction
Fig. 2
Fig. 2
Determination of the frailty index cutoff point using maximally selected rank statistics. Standardized log-rank statistic was utilized in the calculation
Fig. 3
Fig. 3
Kaplan Meier curves of mortality among participants with RA in different frailty index groups
Fig. 4
Fig. 4
RCS illustrates the relationship between frailty index and mortality among participants with RA
Fig. 5
Fig. 5
The relationship between frailty index and all-cause mortality in different age groups
See this image and copyright information in PMC

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