Seniors with rheumatoid arthritis are at high risk of serious infections that could be overlooked, Canadian doctors say.

Rheumatoid arthritis (RA) is a serious inflammatory condition that affects between three to four per cent of seniors. Seniors who have rheumatoid arthritis are vulnerable to infections such as pneumonia that can put them in hospital.

Rheumatoid arthritis affects between three to four per cent of seniors. (iStock)

In Friday's issue of the journal Arthritis Care & Research, researchers estimated that if 100 seniors with rheumatoid arthritis were followed for one year, five would be hospitalized for an infection.

Dr. Sasha Bernatsky, a professor in the rheumatology and clinical epidemiology divisions at McGill University in Montreal, and her co-authors used hospital administrative data to compare infections in RA patients in Ontario over age 66 with other people with rheumatoid arthritis of the same age and sex who weren't diagnosed with an first infection.

"Our findings were interesting on a couple of different levels," Bernatsky said.

First, people with RA and other chronic health problems such as chronic lung disease and kidney disease were at increased risk of infection. Since those diseases were strong predicators, it's a signal that doctors should keep a close watch on them, she said.

"When it came to medication exposures, there were several of these immune suppressing drugs that seem to be associated with an increased risk of infection. But where the dramatic risk was really was for our oldest drug which is prednisone."

Prednisone, a steroid medication, is effective at decreasing immune activity in people with RA and it's often the first drug used. The finding reinforces that it should be prescribed at the lowest possible dose for the shortest time, Bernatsky said.

Disease modifying medications such as methotrexate and newer biologics also seemed to be associated with increased risk of infection although to a lesser degree than prednisone.

Bernatsky said the findings have already made her more cautious in trying to taper people to lower doses of prednisone but that patients shouldn't shy away from trying the medications.

She said doctors are aware of the risks associated with the newest drugs but the risks of prednisone may no longer be top of mind.

For seniors with RA, Bernatsky suggested trying to avoid some infections by getting vaccinated against the flu and strains of pneumonia.

In the study, the types of infections included:

• Respiratory infections.
• Bacterial pneumonia.
• Shingles.
• Skin or soft tissue infections such as cellulitis.

The study, first-authored by Jessica Widdifield, was part of a large project lead by Dr. Claire Bombardier done at Toronto's Institute for Clinical Evaluative Sciences. The Ontario Biologics Research Initiative is funded by the Canadian Institutes of Health Research, the Ontario health ministry and others.

With files from CBC's Amina Zafar