If you're one of the millions of people with allergic asthma or eczema, you may be more likely to develop the wear-and-tear form of arthritis as you age.
This is the main finding from a new study that examined the risk of developing osteoarthritis among people with the two allergic conditions.
The study wasn't designed to say how, or even if, these allergic diseases increase osteoarthritis risk, but the researchers do have a theory.
“Our group has done work showing that mast cells [a type of allergic cell] are increased in numbers in the joints of people with osteoarthritis, and their activity contributes to the development of osteoarthritis,” said study author Dr. Matthew Baker, clinical chief in the division of immunology and rheumatology at Stanford University in Stanford, Calif.
And asthma and eczema may be the tip of the iceberg, he said.
“It is possible that other atopic conditions such as seasonal allergies, food allergies and/or allergic rhinitis [hay fever] may provide a similar risk,” Baker noted.
These researchers did not look at these conditions in the new study.
For the study, they reviewed insurance claims from two databases. The first set included more than 117,000 people with asthma or eczema and 1.2 million people without these conditions. After eight years of follow-up, the risk of developing osteoarthritis was 58% higher among folks with allergic asthma or eczema than among their counterparts without these allergic conditions.
The risk of osteoarthritis was even higher among people who had both allergic asthma and eczema, the study findings showed.
About half of people with eczema also have allergic conditions such as hay fever, asthma or food allergies, according to the American Academy of Allergy, Asthma and Immunology.
The researchers also compared the risk of developing osteoarthritis among people with allergic asthma to those with chronic obstructive pulmonary disease (COPD), a lung disease that doesn't involve allergic pathways. People with asthma were 83% more likely to develop osteoarthritis than those with COPD.
In the second database, the odds of developing osteoarthritis were 42% higher among people with either allergic asthma or eczema and 19% higher among those with both conditions. These findings weren't as robust as those seen in the first set as they took body mass index (BMI) into account. (BMI is a estimate of body fat based on height and weight.) A high BMI is a risk for developing osteoarthritis.
The million-dollar question is whether treating asthma or eczema lowers arthritis risk. The researchers didn't look at this in this study, but there is reason for hope.
Older research has linked the use of antihistamines with reduced structural progression in knee osteoarthritis, Baker said.
“We are hopeful that any number of drugs that work to inhibit mast cells or mast cell products [such as histamine] will reduce the incidence of osteoarthritis," he said.
The study — published March 27 in the Annals of the Rheumatic Diseases — was funded by the U.S. National Institutes of Health.
The connection between osteoarthritis and allergic diseases could be the low-grade inflammation, said Dr. Theodore Fields, a rheumatologist at the Hospital for Special Surgery in New York City, who reviewed the findings.
The good news is that there are more treatments for eczema today than ever before and many more are in the pipeline.
“If treatment of atopic disease helps prevent or lessen osteoarthritis, there are a lot of options and will be more,” Fields said.
“For patients with eczema or asthma, this data can make them aware that they might be more likely to get osteoarthritis,” he said.
If you have an allergic disease and develop aches and pains in your joints, see your doctor, he advised.
"We have many strategies to improve the symptoms of osteoarthritis but don't yet have a disease-modifying treatment,” Fields said.
“There can be some hope in this study for patients with eczema or asthma that their treatment for atopic disease might prevent or diminish their potential to develop osteoarthritis," he added.
The American Academy of Allergy, Asthma & Immunology has more on eczema.
SOURCES: Matthew Baker, MD, clinical chief, division of immunology and rheumatology, Stanford University, Stanford, Calif.; Theodore Fields, MD, rheumatologist, Hospital for Special Surgery, New York City; Annals of the Rheumatic Diseases, March 27, 2023