Adhering to antimalarial treatment offers some protection to patients with systemic lupus erythematosus (SLE) from developing type 2 diabetes mellitus (T2DM), according to new research.

Patients who took at least 90% of their prescribed antimalarial doses were 39% less likely to develop T2DM than patients who discontinued antimalarial therapy. Patients who took less than 90% of their prescribed doses but didn’t discontinue treatment were 22% less likely to develop T2DM.

“[O]ur study provides further support for the importance of adherence to antimalarials in SLE by demonstrating protective impacts on T2DM,” Shahrzad Salmasi, PhD, of the University of British Columbia, Vancouver, and colleagues wrote in Arthritis Care & Research.

Dr. Salmasi and colleagues conducted this retrospective study using administrative health data on patients in British Columbia. The researchers analyzed 1,498 patients with SLE. Their mean age was about 44 years, and 91% were women.

The researchers used data on prescription dates and days’ supply to establish antimalarial drug courses and gaps in treatment. A new treatment course occurred when a 90-day gap was exceeded between refills. The researchers calculated the proportion of days covered (PDC) – the total number of days with antimalarials divided by the length of the course – and separated patients into three categories:

  • Adherent to treatment – PDC of 0.90 or greater
  • Nonadherent – PDC greater than 0 but less than 0.90
  • Discontinuer – PDC of 0

The patients had a mean of about 23 antimalarial prescriptions and a mean of about two courses. The mean course duration was 554 days.

At a median follow-up of 4.6 years, there were 140 incident cases of T2DM. The researchers calculated the risk of T2DM among adherent and nonadherent patients, comparing these groups with the discontinuers and adjusting for age, sex, comorbidities, and concomitant medications.

The adjusted hazard ratio for developing T2DM was 0.61 among adherent patients and 0.78 among nonadherent patients.

“This population-based study highlighted that taking less than 90% of the prescribed antimalarials compromises their effect in preventing T2DM in SLE patients,” Dr. Salmasi and colleagues wrote. “Our findings should be used to emphasize the importance of medication adherence in not only treating SLE but also preventing its complications.”

The researchers reported having no conflicts of interest.

SOURCE: Salmasi S et al. Arthritis Care Res. 2020 Jan 21. doi: 10.1002/acr.24147.