TOPLINE:

Among patients with incident rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE) who were new antimalarial users, adherence to antimalarials (≥ 90% of doses) was associated with a lower risk for hospital admissions and fewer hospital days than nonadherence, with a lower hospitalization cost.

METHODOLOGY:

• Researchers conducted a retrospective cohort study, leveraging linked administrative data from January 1990 to March 2022 from British Columbia, Canada, to evaluate temporal links between adherence to antimalarial medications and subsequent acute care utilization and costs among patients with RA or SLE.
• They included adults with incident RA or SLE since 1997 who had new antimalarial use and more than a year of follow-up.
• Adherence to the antimalarials hydroxychloroquine or chloroquine in the first follow-up year was assessed as the proportion of days covered (PDC), with adherence classified as PDC ≥ 0.90 and nonadherence as 0 ≤ PDC < 0.90.
• The outcomes assessed in the second follow-up year were the numbers of hospital admissions and hospitalized days and the hospitalization cost; costs were computable for the follow-up years 2001-2021.
• Analysis matched each adherent patient to up to two nonadherent patients via greedy propensity score matching using baseline covariates; the final matched cohorts comprised 8768 adherent (mean age, 59.7 years; 73.6% women) and 16,479 nonadherent (mean age, 58.0 years; 74.9% women) patients. Hydroxychloroquine was received by 98.6% of patients.

TAKEAWAY:

• Adherence vs nonadherence to antimalarial therapy was associated with a reduced risk for hospital admissions (adjusted rate ratio [aRR], 0.89; 95% CI, 0.84-0.94) and fewer hospitalized days (aRR, 0.79; 95% CI, 0.71-0.88).
• Hospitalization costs, on average, were lower for patients adherent to antimalarial therapy than for those nonadherent (adjusted mean difference estimate, CAD -$549.64; P < .01).
• In a stratified analysis by initiation timing, reductions in the number of hospitalized days were greater for those who initiated the antimalarial therapy after diagnosis of RA or SLE than for those who initiated the therapy before diagnosis (32% vs 9% lower; P = .009).

IN PRACTICE:

“This evidence only increases the need for physicians to seek better ways to increase adherence to antimalarials used in RA and SLE” the authors wrote.

SOURCE:

This study was led by Md Rashedul Hoque, PhD, Arthritis Research Canada in Vancouver, British Columbia, Canada. It was published online on February 9, 2026, in Arthritis & Rheumatology.

LIMITATIONS:

Case identification for RA or SLE may be inaccurate and could lead to misclassification. Reasons for nonadherence to antimalarials were not available in the data. Adherence estimates were derived from outpatient dispensations with an assumption that medications dispensed were taken.

DISCLOSURES:

This study was supported by PRECISION (Preventing Complications from Inflammatory Skin, Joint and Bowel Conditions), a Team Grant funded by the Canadian Institutes of Health Research, with additional support from the Natural Sciences and Engineering Research Council of Canada. The authors reported having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.