Autoimmunity on the Rise in the US

By Marilynn Larkin

April 20, 2020

NEW YORK (Reuters Health) - The prevalence of antinuclear antibodies (ANA) in the blood of U.S. adolescents and adults has increased over the past 30 years, signaling a rise in autoimmunity, researchers say.

"It is not known if these same increases are occurring in other parts of the world, but since ANA are associated with many autoimmune diseases and some of these diseases are increasing in Europe and other global regions, it could be that similar increases in ANA are occurring in these areas," Dr. Frederick Miller of the US National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina told Reuters Health.

"Immune system responses and immune-mediated diseases result from interactions between our genetic makeup and environmental exposures," he said by email. "Because our genes have not changed much in the last few decades, one or more of the many recent changes in our lifestyles and environmental exposures must be responsible for the ANA increases."

"These changes include different diets, lower physical activity levels, increased life stresses, altered sleep patterns, changing occupations, different pathogens, and exposures to new chemicals and drugs," he added. "Many of these factors have been suspected of altering immune system regulation that could lead to ANA and later autoimmune disease. We are continuing to do research in these areas to define and understand these risk factors (see https://bit.ly/3exaEda). "

As reported in Arthritis and Rheumatology, the researchers analyzed serum ANA from 14,211 participants ages 12 and older in the U.S. National Health and Nutrition Examination Survey for three time periods: 1988-1991, 1999-2004, and 2011-2012 (approximately one third of participants were included in each time period).

The prevalence of ANA was 11.0% in 1988-1991, 11.5% in 1999-2004, and 15.9% in 2011-2012, corresponding to 22 million, 27 million, and 41 million affected individuals, respectively.

Among adolescents (ages 12-19 years), ANA prevalence rose steeply, with odds ratios of 2.02 and 2.88 in the second and third time periods relative to the first.

ANA prevalence increased in both sexes, though more in males, older adults (50 and older), and non-Hispanic whites.

These increases were not explained by concurrent trends in obesity/overweight, smoking, or drinking, according to the authors. Therefore, they state, "Additional studies to determine factors underlying these increases could elucidate cause of autoimmunity and enable development of preventative measures."

Dr. Anca Askanase, Director, Columbia University Lupus Center and Associate Professor of Medicine at Columbia University College of Physicians and Surgeons in New York City, commented in an email to Reuters Health, "While the authors acknowledge several limitations - the cross-sectional nature of the data; self-report of several variables, the limited data on autoimmune diseases; the age of the serum samples - the paper adds to our understanding of current trends in autoimmunity."

"These trends in ANA positivity will have to be confirmed in other cohorts and the implications of this finding evaluated in parallel with prevalence and incidence of autoimmune diseases will need to be further explored," she said.

Dr. Stuart Kaplan, Chief of Rheumatology at Mount Sinai South Nassau in Oceanside, New York, also commented by email, "ANA is a very non-specific test which, while found in many autoimmune conditions, does not by itself necessarily indicate and autoimmune disease. A positive ANA can be found in many different types of inflammatory and infectious conditions, including viruses."

"Thus," he told Reuters Health, "while the finding of an increased incidence of positive ANA is very interesting, further investigation is required to explore possible explanations for this and one can not automatically assume that autoimmune diseases are on the rise."

SOURCE: https://bit.ly/3aiNKTs Arthritis and Rheumatology, online April 7, 2020.

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