Several morbidities, including bipolar disorder, dementia, and vitamin D deficiency, were associated with an increased risk for serious infection among patients with rheumatoid arthritis (RA), according to study results published in Seminars in Arthritis & Rheumatism.
It is important to understand the significant factors contributing to the risk for serious infection and to what extent these risks can be reduced, especially in patients with RA. However, no prior studies have examined the association between serious infection risk and a comprehensive list of morbidities.
To determine this association, researchers conducted a retrospective, observational, population-based cohort study that included adult patients with RA living in 8 counties within Minnesota. Patients were followed-up until death, migration, or until December 31, 2021.
A total of 55 comorbidities were identified using medical records and selected based on their prevalence among the specific patient population. The relationship between each morbidity and the risk for serious infection was evaluated using 3 different conditional frailty models. Serious infections included those that required hospitalization for at least 1 day.
A total of 911 individuals with RA were included in the analysis, 70% of whom were women with a mean age of 56 years. Overall, 293 serious infections were reported among 155 individuals, corresponding to an infection incidence of 3.9 per 100 person-years.
More than half of the participants had multiple comorbidities, the most common of which were osteoarthritis (55.2%), hyperlipidemia (54.6%), hypertension (53.6%), and chronic back pain (53.1%). Serious infections were most frequently reported in the lower respiratory tract (35.5%), the bloodstream/sepsis (28.3%), the skin and soft tissue (14.0%), and the intestines (10.9%).
The risk for serious infection in each of the 55 morbidities was adjusted for age, sex, and calendar year in the first model; 27 morbidities were linked to an increased risk for serious infection. Bipolar disorder was associated with the greatest risk for serious infection, with a hazard ratio (HR) of 4.73 (95% CI, 1.57-14.21). With each additional morbidity, the risk for serious infection was increased by an average of 16%.
The second and third models adjusted for Rheumatoid Arthritis Observation of Biologic Therapy (RABBIT) and Mayo serious infection risk scores, in addition to age, sex, and calendar year. Upon accounting for RABBIT risk scores, 11 of the 55 morbidities were linked to a significantly increased risk for serious infection, while 23 morbidities were associated with an increased risk after accounting for Mayo scores.
Bipolar disorder maintained a marked risk association, emerging as the morbidity with the second-highest serious infection risk, following adjustment for RABBIT scores (HR, 6.23; 95% CI, 2.11-18.41). Bipolar disorder was associated with the greatest risk after adjusting for Mayo scores (HR, 5.24; 95% CI, 2.34-11.73), according to the second and third models.
Additional morbidities that repeatedly ranked within the top 10 for effect size in all 3 adjustment models included dementia, vitamin D deficiency, and sleep apnea.
Furthermore, patients with anemia, chronic kidney disease, chronic skin ulcers, hematologic cancers, post-traumatic stress disorder, liver disease, and leukopenia faced a 2-fold greater risk for serious infection in all 3 models.
Study results were limited by the retrospective and observational nature. Additionally, the use of medical codes to identify morbidities has inherent weaknesses. Moreover, the number of observations that the RABBIT and Mayo risk models could adjust for was limited due to missing data.
Study authors concluded, “Additional studies in other populations are needed to confirm the association between [serious infection] risk and morbidities included in this study, especially morbidities that do not have a clear biologic basis for increasing infection risk.”
This article originally appeared on Rheumatology Advisor
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