Rheumatoid arthritis (RA) is a disease where the body’s immune system mistakenly attacks the joints.

RA affects the lining of the joints, causing pain and inflammation. This inflammation can lead to joint damage, including the destruction of cartilage and bone. RA usually affects multiple joints at the same time, and often the same joints on both sides of the body.

But RA doesn’t just affect the joints. It’s a systemic disease, which means it can cause symptoms in multiple parts of the body and lead to further medical complications.

Scientists don’t fully understand why some people get RA and others don’t. Although the exact cause of RA is unknown, research shows that there are both inherited and environmental risk factors. These factors likely work together to trigger the disease.

What Causes Rheumatoid Arthritis

Scientists do not fully understand what causes RA, but they know some of the ways it starts. RA is an autoimmune disease. This means the immune system, which normally protects the body, attacks healthy parts of the body by mistake.

Rheumatoid Arthritis and the Immune System

Normally, the immune system protects the body by finding and removing harmful substances. It does this by making substances called antibodies that target things like bacteria, viruses, and damaged cells or cancerous cells.

In RA, the immune system makes antibodies that target healthy cells by mistake. Two common autoantibodies (antibodies against self-proteins) found in RA are rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP).

The immune system also releases chemicals called cytokines. These cause inflammation, pain, and swelling in the joints.

Normally, inflammation stops when it’s no longer needed. But with RA, the immune system creates chronic or long-term inflammation. This long-term inflammation damages healthy joint tissue, including bone and cartilage. Over time, it can cause joint deformities. RA treatments aim to reduce inflammation and slow or prevent joint damage and deformity.

1. Family History

RA is not inherited, but having a close relative — like a parent or sibling — with RA puts you at higher risk for developing it. RA affects about 1 percent to 2 percent of the general population, but this number increases if you have a close relative with RA. Unfortunately, family history is a risk factor you can’t change.

2. Genetics

Certain genes may make it more likely for someone to develop RA. While these genetic markers can be passed down from parents to children, having them doesn’t mean you will definitely get the disease.

One example is the human leukocyte antigen DR (HLA-DR) gene. Variations in the HLA gene are linked to a higher risk of RA. Still, not everyone with these gene changes develops the condition.

3. Biological Sex

According to the Centers for Disease Control and Prevention (CDC), RA affects women two to three times more often than it does men. Researchers think one reason for this increased risk may be related to hormones like estrogen and their effects on the immune system. Like genetics and family history, biological sex is another risk factor you can’t control.

4. Age

The risk of RA increases with age. About 5 percent of women over the age of 55 have RA, compared to 1 percent to 2 percent of people of all ages. The age group with the highest number of RA cases is people between 50 and 59 years old. According to Cleveland Clinic, RA typically develops between the ages of 30 and 60, but children and people older than 60 can develop it, too.

5. Smoking

Past or present cigarette smoking significantly raises your risk of RA. This may be because of how smoke exposure affects the immune system. Studies show that smoking more cigarettes and smoking for longer periods both increase your risk. Your risk for RA can stay higher than average for years after you quit smoking.

Exposure to secondhand smoke during childhood may raise the risk of getting RA later in life. However, scientists don’t all agree on how strong this link is.

If you already have RA, smoking can trigger flares and make arthritis symptoms worse, since it causes inflammation and has other harmful effects on the body. If you smoke, talk to your healthcare provider about ways to quit. They can help you find a strategy that works for you.

6. Obesity

Obesity — defined as a body mass index (BMI) of 30 or higher — can raise the risk of developing RA. According to the Arthritis Foundation, the more overweight someone is, the more severe their RA symptoms, such as pain and disability.

Fat cells produce chemicals that release inflammatory proteins. The more body fat a person has, the more inflammation they may have throughout their body. This can worsen existing inflammation.

Some research suggests that obesity might make RA treatments less effective, but scientists are still studying this link. If you’re living with both RA and obesity, talk to your healthcare provider. Managing both conditions together can help you feel better and protect your joints.

Flare Triggers for Rheumatoid Arthritis

RA can sometimes go into remission. This means a period of minimal or no symptoms that can last for months or years. During a flare, your symptoms may become worse, and you might get new symptoms. Sometimes the cause of a flare is clear. These are called predictable flares. Other times, flares happen without reason (unpredictable flares).

Flares can cause increased joint pain, swelling, and stiffness. Doctors don’t all agree on exactly what defines a flare. Repeated flares may be a sign that your current medication isn’t working well.

If you have a flare that lasts longer than two days, contact your healthcare provider. Early treatment can help reduce the long-term worsening and risk of complications from RA.

Flare triggers vary from person to person. Some common ones include:

• Emotional stress
• Overexertion
• Not getting enough sleep
• Infections
• Changes in medications
• Certain foods

Talk to Your Doctor

If you or a loved one is living with RA and has questions about causes, symptoms, or treatments, talk to your healthcare provider. They can help you better understand your condition and create a treatment plan that works best for your needs.

Find Your Team

On myRAteam, the social network for people with rheumatoid arthritis and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with RA.

Have you wondered what caused your RA? Share your experience in the comments below, or start a conversation by posting on your Activities page.