Arthritis can affect more than your joints; it can cause other health problems throughout the body. Certain types of arthritis may even play a role in cancer, as researchers recently found.

Some patients with juvenile idiopathic arthritis were almost three times more likely to develop cancer, compared to those without juvenile arthritis.

Juvenile idiopathic arthritis is an autoimmune disease, meaning the body’s immune system mistakenly attacks healthy tissues. This attack involves inflammation – a process that also happens in cancer.

With this relationship between arthritis and cancer in mind, Beth L. Nordstrom, PhD, MPH, of United BioSource Corporation, and colleagues wanted to see if patients with juvenile idiopathic arthritis were diagnosed with cancer more often than patients without juvenile arthritis.

They found that the rate of cancer among juvenile arthritis patients was 67 cases per 100,000 person-years. In comparison, the rate of cancer among those without juvenile arthritis was 23.2 cases per 100,000 person years.

In other words, patients with juvenile arthritis were diagnosed with cancer more often than those without juvenile arthritis.

In addition, biologics-naive juvenile arthritis patients (those who have not taken biologic drugs) had a higher risk of cancer, with a hazard ratio of 2.8.

A hazard ratio explains how much an event happens in one group versus another over a period of time. In this case, that event was cancer. The hazard ratio of 2.8 means that juvenile arthritis patients not taking biologic drugs had nearly three times the risk of cancer.

The study included 3,605 people with juvenile idiopathic arthritis and 37,689 people without the condition.

The research was funded by Wyeth/Pfizer.

Study co-authors Dr. Yun Gu and Dr. Peter Aquino disclosed possible conflicts of interest with Pfizer and Wyeth. Dr. Mines owns shares in the Vanguard Healthcare mutual fund.

The study was published August 27 in Arthritis Care & Research, a journal of the American College of Rheumatology.