According to the American Autoimmune Related Diseases Association, the majority of the 24 million individuals living with an autoimmune disease in the United States are women.
In fact, women are three times more likely than men to develop an autoimmune disease. In the case of lupus, women have a nine times greater chance of developing the disease.
But, why are women more likely to be diagnosed with an autoimmune condition than men?
Researchers at the Sahlgrenska Academy in Sweden think they have the answer: Women lack testosterone.
The Swedish researchers believe women have an increased risk of autoimmune disease because testosterone helps to keep B cells in check; testosterone suppresses the protein known as BAFF, or B-cell activating factor. B cells are part of the immune system's defense against germs; they produce the antibodies needed to kill off foreign invaders.
Autoimmune disease develops when the immune system sees one of the body's tissues or organs as an attacker and tries to kill it. During the body's attack on itself, most individuals experience inflammation, pain and fatigue.
"When the body senses it is under attack, it tells the body to ramp up antibody production, which results in inflammation," said Dr. Bill Johnson, a Dallas, Texas, stem cell physician who treats both men and women living with autoimmune diseases with fat stem cell therapy.
Fat stem cell therapy reduces the inflammation associated with many autoimmune diseases.
"Inflammation is a common side effect of all autoimmune conditions," Johnson said.
Without testosterone to keep B cells' production of antibodies in check, the immune system can attack whatever tissue or organ it senses is a danger.
"Attacks, also known as flares, can last several days or weeks," Johnson said.
During flares, those living with an autoimmune disease see an increase in symptoms, which can be debilitating.
"Flares can negatively impact the quality of life for many sufferers," Johnson said.
The authors of the Swedish study also examined the interaction between B cells and testosterone cells to understand how the relationship between the two are managed in the spleen, but they were unable to develop a clear understanding of their relationship.
Other studies have shown a relationship between BAFF and the presence of lupus and other autoimmune conditions. BAFF inhibitors have been used to stop the activation of B cells for some people living with autoimmune diseases such as lupus, but these drugs have not shown significant benefits for most users.
Those working on the study also hope their research can help determine who would benefit from BAFF inhibitors.
Besides gender, other factors contribute to the risk of developing an autoimmune condition, such as genetics.
"If your mother, grandmother or aunt has lupus, you have a greater chance of developing lupus, too," Johnson said.
Age also plays a role; most people are diagnosed in younger and middle-aged people — however, some conditions, such as rheumatoid arthritis, develop later in life.
Other research has shown that if a person has an autoimmune disease, their relatives have a higher risk of developing an altogether different autoimmune condition.
Another risk factor for developing autoimmune disorders is living with someone who has celiac disease, an autoimmune condition that causes a severe reaction to gluten.
Ethnicity also plays a role in developing an autoimmune disease; individuals who are African American, American Indian or Latino have a higher risk of developing autoimmune disorders than Caucasians.
"Another factor in being diagnosed with an autoimmune disease is already having another autoimmune disease," Johnson said.
Around 25 percent of those living with an autoimmune condition end up being diagnosed with additional autoimmune disorders. This situation is known as multiple autoimmune syndrome, or MAS. Although MAS is rare, some researchers believe it is on the rise.
University of Gothenburg. "New theory on why more women than men develop autoimmune diseases." ScienceDaily. ScienceDaily, 5 June 2018.
Very Well Health. What Is Multiple Autoimmune Syndrome? 29 May 2018.