4 December 2019

When do RA comorbidities appear?

Clinical Rheumatoid Arthritis

Patients with rheumatoid arthritis often have more than that one condition, but sometimes the comorbidities are detected after RA diagnosis. And sometimes certain medical conditions precede the RA diagnosis.

Knowing the average timing of the onset of these comorbidities could potentially be quite helpful for GPs and rheumatologists.

For example, if a patient develops a condition that is known to be linked to RA, GPs could be alerted to the increased possibility of the patient developing RA in the future, enabling early diagnosis and treatment.

Similarly, if rheumatologists are aware which conditions are more likely to develop after RA diagnosis, they can be on the lookout for these as part of their routine management. 

That’s the logic behind a study by the Mayo Clinic in the US, which determined the type and timing of comorbid conditions in around 800 patients with RA.

The study was retrospective, but each patient with RA was compared with three controls matched by age and sex.

Previous large-scale studies have investigated the comorbidities associated with RA, including studies in China and Korea, as well as one international study across 17 countries.

The Mayo Clinic study aimed to address the gaps in previous studies by including information on the timing of comorbidity development and accounting for confounding factors such as smoking, the authors said.

Out of 74 comorbid conditions identified in the study, 11 were linked to RA.  These were:

  • cataracts
  • epilepsy
  • fibromyalgia
  • gastroesophageal reflux disease
  • inflammatory bowel disease (IBD)
  • myocardial infarction
  • obstructive sleep apnoea
  • osteoarthritis
  • pulmonary fibrosis
  • other rheumatic autoimmune disorders; and
  • venous thromboembolism (VTE)

After patients were diagnosed with RA, they were more likely to have a myocardial infarct than those in the control group.

Venous thromboembolism was more likely in patients with RA than the control group, both before and after the RA diagnosis.

Prior to the RA diagnosis, three other conditions were more common compared with controls. These were inflammatory bowel disease, type 1 diabetes and osteoarthritis.

The study showed that patients who eventually developed RA  had nearly four times the risk of having IBD than controls.

“Monitoring patients with IBD for RA may be warranted,” the authors said.

The results around type 1 diabetes “highlight the importance of increased suspicion of RA in patients with autoimmune diseases, and vice versa,” the authors said.

Among those patients who had both epilepsy and RA, the epilepsy was diagnosed prior to the RA being diagnosed in nearly two thirds of cases, which suggested it might be a useful marker to indicate increased predisposition to RA, the authors said.

Surprisingly, prior to a diagnosis of RA, patients did not have a greater number of medical conditions compared with controls, meaning that the RA disease processes or treatments might trigger the development of certain comorbidities, the authors said.

“These findings have important implications for understanding RA pathogenesis, promoting earlier detection of RA, and screening for comorbidities among RA patients,” the authors concluded.

Mayo Clinic Proceedings 2019, 19 November