If a parent or close relative has rheumatoid arthritis (RA) – a potentially debilitating autoimmune disease – you may wonder if you will develop it too. The answer is probably not. You can inherit a susceptibility to RA, but not the disease itself. According to the American College of Rheumatology (ACR), relatives of people with RA have a 0.8% risk of developing it, compared to 0.5% for people with no family history.

You may have heard that the heritability of RA is about 60%; that doesn’t mean the ACR statistics are wrong. Heritability is an estimate of the extent to which genes explain the risk of disease in a population. Sixty percent heritability does not mean that 60% of RA cases are hereditary; this means that genes account for more than half of the susceptibility to RA found in Northern Europeans, who dominate most genetic studies. It is also becoming clearer that genetic risk for RA varies between races and ethnicities.

Most scientists believe that RA, although not well understood, usually results from the interaction of genetic susceptibility and environmental and lifestyle factors. An increasingly important school of thought also focuses on epigenetics. This refers to the way factors such as diet or exercise change the way genes work. Although epigenetic changes do not alter DNA, they can be passed on to future generations. There are certain risk factors for rheumatoid arthritis that you cannot change, but others that you may be able to control.

RA risk factors you can’t control

• Age. Conventional wisdom says that the chance of RA increases with age. But experts say that RA that develops after age 60 — called late-onset RA — is different from RA in younger people. Also, as you get older, the risk may not be as great as originally thought; Current research shows that RA antibodies develop many years before symptoms appear.
• Biological sex. RA is far more common in people born female than those born male. The difference is often due to hormones, primarily because RA can get better or worse when hormones change. Still, studies on the relationship between RA and sex hormones show mixed results. More recent theories focus on women’s more robust immune response to infections, which generate more antibodies, and on differences in the innate immune system.
• Your genes. Hundreds of gene variants, particularly a genetic marker called the shared epitope, are associated with RA, but their exact role is not clear. Many people who have these gene variants never develop RA, while others who do not have them develop arthritis or other autoimmune diseases. Genes can affect the progression of RA or response to treatment, but are not enough by themselves to cause the disease.

Environmental risk factors

You may not always be able to avoid environmental risk factors such as infections and toxins, but it’s important to know that they can trigger RA, especially in genetically susceptible people.

• Infections. Epstein-Barr virus, Escherichia coli (E. coli), and hepatitis C have been suggested as possible causes of autoimmunity and RA. One theory is that the immune system overreacts to infections, creating chronic inflammation and ultimately autoimmune arthritis. Some researchers also believe that there may be cross-reactivity between certain antibodies and healthy cells. Normally, antibodies only attack a single antigen, but antibodies produced against e.g. Epstein-Barr can also target normal tissue.
• Toxins. Lots of different toxins, pollutants and chemicals have been linked to RA, but not all are proven. Those that have a clear link include passive smoking, asbestos, silica dust and pesticides. Chronic pneumonia is known to lead to the formation of autoantibodies, and researchers speculate that these may travel from the lungs to distant sites, including the joints. It is likely that many more toxins are implicated in RA, but more research is needed to find the worst offenders.
• Childhood trauma. Violence, abuse and neglect in childhood are increasingly associated with RA in adults. Emotional distress is known to trigger an immune response that can lead to autoimmune disease. It is also one of the factors that influence arthritis pain and other symptoms. In one study, adults with RA and a history of childhood trauma were found to have significantly more pain than matched patients without a traumatic background.

Lifestyle risk factors

A healthy lifestyle can help prevent RA, regardless of your genetic risk. Some rheumatologists say the new paradigm for RA is to treat it as a preventable condition, like heart disease, in part because it is possible to control some common risk factors, including:

• Smoking. Tobacco smoke is a known risk factor for RA as well as heart disease and a host of other chronic conditions. It is involved in the transition from pre-clinical RA, when you have autoantibodies but no symptoms, to full disease. It can even trigger RA in someone who is not genetically susceptible, especially in those who smoke at least one pack a day for 20 years or more. If you already have RA, smoking can make your treatment less effective and your symptoms more severe.
• Obesity. Being overweight can trigger systemic inflammation because fat cells release inflammatory proteins called cytokines, which play a fundamental role in the destruction of joint tissue. The more fat cells you have, the more cytokines your body produces. Being overweight or obese also makes you less likely to respond adequately to arthritis medication or achieve disease remission.
• Gum diseases. It is now well established that gum disease is a factor in causing RA as well as lung disease, heart disease and Alzheimer’s. Your mouth has more than 700 species of bacteria. Most of the microbes are beneficial and help keep harmful bacteria at bay. When harmful bacteria override these defenses, you can develop gingivitis and mouth cancer. You can also aspirate bacteria into your lungs, where they cause massive inflammation. The inflammation can then spread to other parts of your body, including your joints.
• Food. Although there is no specific gout diet, the type of food you eat affects all aspects of your health. Avoiding some foods, such as red meat, dairy products, sugar and high-fructose syrup, and emphasizing fish, vegetables and olive oil, can make a difference in whether you develop gout as well as improve existing symptoms.
• Changes in the microbiome. In the past 20 years, the microbiome—the large communities of beneficial microorganisms that live on and in the body—has been recognized as a critical determinant of health and disease. This is especially true for autoimmune diseases such as RA, because the microbiome regulates and is regulated by the immune system. Although every nook and cranny of the body has a microbiome, those in your mouth and gut are the most extensive and have the biggest impact on your health. Ideally, trillions of microorganisms in these communities work in harmony to maintain a state of balance that helps prevent disease. When this balance is disturbed, some beneficial species of microbes lose their dominance and others that may be harmful or present in smaller numbers take over. When this happens, you are more likely to develop chronic conditions such as diabetes, metabolic syndrome or RA. The composition of your gut microbiome can vary depending on your age (the microbiome changes as you get older), diet, race, ethnicity, and where you live. It is not clear what a normal microbiome looks like. However, it is clear that people with RA and other autoimmune diseases have different proportions of gut microbes compared to healthy people. They also have less – sometimes far less – microbial diversity. The loss of certain microorganisms means that there is less protection against inflammation and autoimmunity. Leaky gut, another risk, occurs when inflammation and changes in the composition of the microbiome make the gut wall more permeable and allow bacteria to escape into the rest of the body. This produces even more inflammation and can eventually lead to RA. Many things can disrupt the balance of the microbiome, with antibiotics topping the list. But certain foods, especially red and processed meat, sugar and dairy products, as well as stress, lack of exercise, trauma and alcohol consumption also contribute. Scientists believe that we shape the microbiome almost as much as it shapes us.

Given that these and other risk factors for RA are within your control, you have every reason to feel positive about your ability to help you and your family stay healthy.