What Is Arthritis?
Arthritis literally means joint inflammation. But the term is often used to refer to any of the more than 100 diseases that affect the joints – where two or more bones meet to allow movement. Currently, there are 46 million people diagnosed with arthritis in the United States. The most common types of arthritis are:
Osteoarthritis – a condition in which the joint cartilage – the tough, smooth shock-absorbing tissue that covers the ends of the bones where they meet – breaks down, causing pain and stiffness.
Rheumatoid arthritis – a condition in which the body’s immune system attacks the thin membrane (synovium) that lines the joints, causing pain, swelling, inflammation, redness, heat and, if not stopped, joint destruction.
What Is Diabetes?
Affecting an estimated 20.8 million Americans, diabetes is a condition in which the body does not produce or use the hormone insulin sufficiently. Insulin carries glucose (sugars) in the foods you eat into cells, so it can be converted into energy. Without insulin, glucose remains in your blood (raising blood glucose levels), your cells are starved of energy, and you feel fatigued. If not controlled, high blood glucose levels can cause damage to the nerves, and large and small blood vessels, which can lead to further problems such as heart attack, stroke, kidney disease and eye damage.
There are two major types of diabetes:
Types 1 and 2. In type 1, the body does not produce enough insulin. In type 2, the body does not sufficiently respond to the insulin it makes in a process called insulin resistance. This makes it harder for insulin to enter cells and provide them with energy. In both types of diabetes, blood glucose levels begin to rise and damage cells throughout the body.
Are Arthritis and Diabetes Related?
Arthritis and diabetes are not directly related, but the diseases often overlap. In fact, recent reports from the Centers for Disease Control and Prevention (CDC) found that more than half (52 percent) of people with diabetes also have arthritis. The two diseases have several other commonalities depending on the different chemicals in the body that reduces glucose levels.
Recent research suggests that some of the biologic agents used to stop inflammation and joint destruction in RA may also be useful in improving insulin resistance in people with inflammatory diseases or controlling glucose levels in people with type 2 diabetes. However, presently, none of the biologic agents are FDA-approved for those uses.
Rheumatoid Arthritis and Type 1 Diabetes
Type 1 diabetes is an autoimmune disease as is rheumatoid arthritis (RA). In people with type 1 diabetes, the body’s immune system attacks the pancreas, the organ where insulin is made, much in the same way it attacks the synovial lining of the joints in RA.
Levels of inflammatory markers such as C-reactive protein (CRP) and interleukin-1 (IL-1), which are often high in people with rheumatoid arthritis, are also increased in those with type 1 diabetes. One study of people who had type 1 diabetes longer than five years shows an increase in tumor necrosis factor-alpha, another inflammatory marker often elevated in people with inflammatory forms of arthritis.
Research also shows genetic connections between rheumatoid arthritis and type 1 diabetes. In recent years, researchers have identified a gene called PTPN22 that strongly correlates with the incidence of type 1 diabetes as well as rheumatoid arthritis, juvenile idiopathic arthritis and other autoimmune diseases.
Osteoarthritis and Type 2 Diabetes
Because osteoarthritis (OA) and type 2 diabetes are both common conditions, they are likely to occur together by coincidence. But the two share at least two major risk factors: age and weight.
Age: Osteoarthritis is largely a disease of wear and tear on joints. The older you are, the more you have used your joints, making OA more likely. The risk for type 2 diabetes also increases with age, largely because people become less active, gain weight and lose muscle mass as they age. Half of all people diagnosed with diabetes are over 55.
Weight: Obesity affects the joints by increasing the stress on them. For every pound you gain, you add four pounds of pressure on your knees. Over time, the added stress contributes to joint wear and tear. Obesity also affects the internal organs. Fatty tissues of the body produce chemical compounds that increase insulin resistance, which increases blood glucose levels. The heart and blood vessels become stressed as they strain to pump blood through a larger body mass and contend with the inflammatory chemicals being produced by fat cells.
No, arthritis does not cause diabetes and diabetes does not cause arthritis. However, diabetes does sometimes have accompanying joint symptoms, and a sedentary lifestyle and obesity can contribute to or worsen both. Also, taking corticosteroids has been shown to interfere with glucose metabolism and could lead to type 1 diabetes.
Joint Pain and Diabetes
In addition to its connections with these specific forms of arthritis, diabetes causes musculoskeletal changes that lead to symptoms such as joint pain and stiffness; swelling; nodules under the skin, particularly in the fingers; tight, thickened skin; trigger finger; carpal tunnel syndrome; painful shoulders; and severely affected feet.
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