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Lim SY, Lu N, Oza A, et al. Trends in Gout and Rheumatoid Arthritis Hospitalizations in the United States, 1993-2011. JAMA. 2016;315(21):2345–2347. doi:10.1001/jama.2016.3517
Gout and rheumatoid arthritis are the 2 most common inflammatory arthritides. As hospitalizations for these conditions incur substantial resource use, hospitalization trends and associated costs provide key benchmarks of disease burden. However, relevant long-term data are scarce.
We evaluated US hospitalization trends of gout and rheumatoid arthritis from 1993-2011. We investigated these 2 arthritides simultaneously, as we hypothesized opposing trends (due to improvement in rheumatoid arthritis care and a worsening in gout epidemiology1 and suboptimal care2) and as each condition would serve as an internal comparison for the other.
Hospitalization trends of rheumatoid arthritis and gout were studied using data from the 1993-2011 releases of the Nationwide Inpatient Sample (NIS), a database representative of hospitalizations in the United States.3 The NIS is a 20% stratified sample of all nonfederal hospitals in the United States; sampling weights were used to obtain national estimates. Patients 18 years and older who were hospitalized during the study period with a principal discharge diagnosis of gout (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] codes: 274.0-274.9) or rheumatoid arthritis (ICD-9-CM codes: 714.0, 714.2, 714.30-714.33) were included. We focused on principal discharge diagnoses to capture hospitalizations for rheumatoid arthritis or gout, which also maximizes the validity of the case definition,4,5 and calculated annual population rates of hospitalizations and relevant surgeries (total knee replacement, total hip replacement, other major joint surgeries). We calculated inflation-adjusted hospital costs for gout and rheumatoid arthritis by merging the NIS charge data with cost-to-charge ratios (available after 2000) from the Healthcare Cost and Utilization Project. Statistical analyses included Poisson regression models using SAS (SAS Institute), version 9.3. P values were 2-sided with a significance threshold of less than .05. This study was exempt from review according to the Partners institutional review board.
There were 254 982 hospitalizations for gout (mean age, 66.7 years; men, 66.4%) and 323 649 hospitalizations for rheumatoid arthritis (mean age, 61.0 years; men, 21.5%) between 1993 and 2011. Demographic characteristics were similar over the study period.
From 1993 to 2011, the annual hospitalization rate for patients with a principal discharge diagnosis of rheumatoid arthritis declined from 13.9 (95% CI, 13.7-14.1) to 4.6 (95% CI, 4.5-4.7) per 100 000 US adults (P < .001), whereas that for gout increased from 4.4 (95% CI, 4.3-4.5) to 8.8 (95% CI, 8.7-8.9) per 100 000 US adults (P < .001) (Figure and Table). These trends persisted among age and sex subgroups (Table).
The annual hospitalization rate for joint operations among patients with a principal discharge diagnosis of rheumatoid arthritis steadily declined from 8.4 (95% CI, 8.3-8.5) to 2.1 (95% CI, 2.0-2.2) per 100 000 US adults (P < .001). The corresponding surgery rates for gout were 0.09 (95% CI, 0.08-0.11) and 0.17 (95% CI, 0.15-0.19) per 100 000 US adults (2% of hospitalizations for gout).
From 2001 to 2011, the inflation-adjusted hospital costs per 100 000 US adults with a principal discharge diagnosis of gout increased from $34 457 (95% CI, $33 855-$35 059) to $58 003 (95% CI, $57 218-$58 788), whereas the costs for rheumatoid arthritis declined from $83 101 (95% CI, $81 852-$84 350) to $55 988 (95% CI, $54 942-$57 034).
Primary hospitalization rates for gout increased substantially over nearly 2 decades in the United States, whereas those for rheumatoid arthritis declined. In 1993, hospitalizations for rheumatoid arthritis were more frequent than for gout; however, these contrasting trends led to a higher hospitalization rate for gout than rheumatoid arthritis in 2011. These trends were reflected in the inpatient economic burden and persisted across demographic subgroups. The study focus on principal diagnoses helped minimize misclassification, but may have missed cases that secondarily contributed to hospitalizations. The study spanned 19 years until 2011 although was limited by the unavailability of more recent data.
The findings may reflect suboptimal care received by gout patients2 and its increasing prevalence.1 Furthermore, the findings provide a benchmark for rheumatoid arthritis care over the past 2 decades,6 including the reduced frequency of joint replacements and other major joint operations related to rheumatoid arthritis. Although the rheumatoid arthritis data are encouraging, the gout findings suggest the need to improve care and prevention.
Corresponding Author: Hyon K. Choi, MD, DrPH, Division of Rheumatology, Allergy and Immunology, Department of Medicine, Massachusetts General Hospital, 55 Fruit St, Bulfinch 165, Boston, MA 02114 (firstname.lastname@example.org).
Author Contributions: Drs Lim and Choi had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Lim, Lu, Fisher, Menendez, Choi.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Lim, Lu, Oza, Rai, Choi.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Lim, Lu, Rai, Choi.
Administrative, technical, or material support: Lim, Lu, Oza, Rai, Menendez, Choi.
Study supervision: Lim, Fisher, Menendez, Choi.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Choi reports receiving a research grant from AstraZeneca and serving as a research consultant for Takeda. No other disclosures were reported.
Funding/Support: This work was supported in part from grant R01AR065944 from the National Institute of Arthritis and Musculoskeletal and Skin Diseases.
Role of the Funder/Sponsor: The funding agency had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, and approval of the manuscript; and decision to submit the manuscript for publication.