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Marker of autoimmunity increases in U.S.

The study was prompted by reports that autoimmune diseases like lupus and myositis have been increasing in the U.S. Chainarong Prasertthai / iStock / Getty Images

A healthy immune system protects the body against infection by attacking bacteria, viruses, and other foreign invaders. In people with autoimmune diseases, the immune system malfunctions and turns against the body’s own organs and tissues. Common autoimmune diseases include rheumatoid arthritis, lupus, type 1 diabetes, and inflammatory bowel disease.

The causes of most autoimmune diseases aren’t well understood. Genes, in combination with infections and other environmental exposures, are believed to play a role.

Doctors can conduct blood tests to look for markers of autoimmune diseases. The presence of antinuclear antibodies (ANA) in the blood is the most common biomarker of autoimmunity. These antibodies are called “antinuclear” because they target the nucleus—the large organelle that contains our chromosomes—of healthy cells. 

Recent studies have suggested that autoimmune diseases like lupus and myositis are on the rise in the U.S. However, this increase may be due to greater recognition and diagnosis.

Researchers led by Dr. Frederick Miller at NIH’s National Institute of Environmental Health Sciences (NIEHS) investigated whether the prevalence of ANA had changed over a 25-year span. Their study is the first to evaluate ANA changes over time in a representative sample of the U.S. population. Findings appeared in Arthritis and Rheumatology on April 7, 2020. 

The team measured ANA in blood serum samples from more than 14,000 participants, 12 years and older, in the U.S. National Health and Nutrition Examination Survey (NHANES). The prevalence of ANA was measured over three time periods.

The researchers found ANA in 11.0% of subjects in 1988-1991, 11.5% in 1999-2004, and 15.9% in 2011-2012. These percentages corresponded to 22, 27, and 41 million ANA-positive individuals, respectively.

Some people without autoimmune disease can carry ANA. In the general population, women, older adults, and individuals exposed to certain drugs and chemicals are more likely to have the antibodies. These findings, however, suggest that the prevalence of ANA has increased considerably in recent years, particularly among males, adults 50 years and older, and non-Hispanic whites.

Among adolescents, ANA prevalence rose steeply. For those 12-19 years of age, positive ANA tests doubled and then nearly tripled over the three time periods (from 5% to 9% to 13%).

“The reasons for the increases in ANA are not clear, but they are concerning and may suggest a possible increase in future autoimmune disease,” Miller says. “These findings could help us understand more about the causes of these immune abnormalities and possibly learn what drives development of autoimmune diseases and how to better treat and prevent them.”