Health outlooks for the most common form of arthritis

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This transcript has been lightly edited for clarity.

PAULINE CHIOU: Welcome to Global Health Insights, a podcast from the Institute for Health Metrics and Evaluation, or IHME. I’m Pauline Chiou in media relations at IHME. In this episode, we will discuss something that many of us deal with, osteoarthritis, the most common form of arthritis. A new study projects close to 1 billion people will be dealing with osteoarthritis by 2050.

This study is now published in The Lancet Rheumatology journal. And we have the research team with us: Dr. Jaimie Steinmetz, who’s lead research scientist at IHME and corresponding author of this study. Dr. Liane Ong, also a lead research scientist at IHME, who supervised the study and is coauthor of the paper. 

And Dr. Jacek Kopec, senior author of the paper, Professor Emeritus at the School of Population and Public Health at the University of British Columbia, who has done more than 30 years of research on arthritis. Thank you to the three of you for being here on this podcast. Dr. Kopec, let me start with you. What is osteoarthritis and how does it compare to other forms of arthritic conditions, and why should we explicitly focus on it rather than lumping it all together with other forms of arthritis?

DR. JACEK KOPEC: Osteoarthritis or OA is also known as degenerative joint disease. In OA, the cartilage breaks down and bone spurs develop around the joint margins, causing pain, stiffness, and limitations in activity. These changes develop slowly over many years such that OA is rare before age 40. OA is often found in the knees, hips, and hand, but it can affect any joint. OA should be distinguished from inflammatory arthritis such as rheumatoid arthritis, in which chronic inflammation involving joints and other organs is the main feature.

It’s important to talk about OA specifically because it is the most common form of arthritis. About half of all people will develop OA over their lifetime, and different types of arthritis also differ in the factors that increase the risk of developing the disease. For OA, the main risk factors other than age are obesity and joint injury.

In addition, certain occupational activities and sports can increase the risk, especially in persons with genetic predisposition.

PAULINE CHIOU: And we’re going to touch on some of those factors that you mentioned. Dr. Steinmetz, your team looked at arthritis data from all around the world. What would you say the key messages are from this paper?

DR. JAIMIE STEINMETZ: Thanks, Pauline. So a few key messages just to echo what’s already been said.

We estimate that almost 600 million people lived with and experienced osteoarthritis in 2020. So it’s really common – it’s the second most common of the musculoskeletal conditions that we work on in the Global Burden of Disease study, and the most common form of arthritis. And we think it’s really important to note that if the current trends continue, we’ll get close to 1 billion people by the year 2050.

We also show that osteoarthritis increases with age. So about 15% of people over the age of 30 have osteoarthritis. We think it’s also worth noting that about 3.5% of working adults, so those aged around 30 to 60, experience OA. So even though it gets more common as we get older, certainly you can see osteoarthritis in working- or younger-age adults, this climbs up to, you know, 40–50% in older age, say over the age of 80.

We looked at four different sites of osteoarthritis or four different joint sites: hand, knee, hip, and other joints, like the elbow or shoulder, and found that knee is the most common globally, followed by hand. And just in general, I want to emphasize that given its commonality, OA can cause pain and decreased mobility, it’s very common in joints like the knee and hand that we depend on for independence, we think this is really a key condition to highlight and address.

PAULINE CHIOU: And it’s really striking when you say 15% of cases are over the age of 30 because just the general public doesn’t, I think, realize that it can strike someone at that young of an age. Another issue that’s been mentioned is obesity. Dr. Ong, we see obesity as a factor when we talk about different diseases and conditions that we study here at IHME and, again, it has surfaced. What is the role of obesity when it comes to osteoarthritis?

DR. LIANE ONG: Thank you, Pauline. Well, what we believe and what we know is that obesity adds extra weight onto our joints, and it puts extra pressure. And that can cause accelerated damage. It can cause increased amounts of pain, and it can lead to more severe forms of OA.

And so that’s really where we see the impact of the obesity situation that’s occurring throughout the world. And as we have been studying obesity in other places within IHME, we know that those trends are expected to increase, which actually is a bit of a canary in the coal mine for things like OA, where we know that there’s a relationship between the two.

And so, as Dr. Steinmetz had just said, that where we expect to see such a large increase by 2050, we can definitely take that next logical leap to understand that a lot of that will likely be due to the increasing amounts of obesity that we’re expecting to see in the population.

PAULINE CHIOU: Another observation that we saw from the paper is gender differences. Osteoarthritis seems to strike more with women than men. And this is for anyone here. Why is that?

DR. JAIMIE STEINMETZ: I can jump in here. So as you say, we show that osteoarthritis is about 40% more common in women than men. And in particular, we see this in the most common forms of OA, so in hand osteoarthritis and knee osteoarthritis. And then for the other forms of osteoarthritis and hip OA, we see about the same commonality between men and women.

So researchers are investigating why this is. It’s a bit beyond the scope of our studies, but a few hypotheses include genetics, anatomical differences, and maybe stress on the joints or gait differences, and then also hormonal factors. So it’s been shown that estrogen levels can impact joint tissue integrity, and there’s a decrease in estrogen at menopause, which could be linked to increasing rates of OA in women say over the age of 50 compared to men.

PAULINE CHIOU: And Dr. Kopec, the projection, as we mentioned already, is that 1 billion people will have osteoarthritis less than 30 years from now. What is the main message to send to the public and policymakers about osteoarthritis? And again, it’s the most common form of arthritis in terms of care and the resources that are needed.

DR. JACEK KOPEC: Well, I think the main message is that we need a comprehensive global initiative on OA, involving research, prevention, treatment, and rehabilitation.

So first, we need better data. We know that OA is a leading cause of disability. It has enormous impact on population health and health care costs. And as we have shown, the burden of OA will continue to rise. At the same time, we don’t have sufficient data on OA in most countries; therefore allocating more funding for OA research is critical.

Second, we should point out that OA is not an inevitable consequence of age. It has specific causes and risk factors, and it can be prevented. How? By avoiding joint injuries, maintaining healthy weight, and regular low-impact exercise to keep the muscles strong. So from a policy perspective, a stronger focus on prevention would be an effective burden reduction strategy.

And finally, although we don’t have a cure for OA, we do have interventions that can alleviate symptoms and improve quality of life. For patients, it is crucial to get enough information about the various treatment options. These options include non-pharmacologic interventions such as exercise and diet, proper use of pain medication, mainly non-steroidal anti-inflammatory drugs, and surgery – in advanced knee or hip OA, joint replacement surgery is usually very effective in relieving pain and restoring function.

For policymakers, an important goal should be to ensure that these treatments are equally accessible to everyone.

PAULINE CHIOU: So if our listeners want to get more on the discussion and on the data that you found, they can read your study in The Lancet Rheumatology journal. Dr. Jacek Kopec, Dr. Liane Ong, and Dr. Jamie Steinmetz, thank you so much for talking about osteoarthritis with us.

PANEL: Thank you.