Health care system spending on patients in the United States with giant cell arteritis—a little-known chronic disease of the blood vessels affecting 230,000 Americans—is $16,400 more in the first year following diagnosis compared to similar patients without the disease, according to a new study from the University of Washington School of Public Health.

“In addition to its significant clinical burden, giant cell arteritis has a substantial economic impact, as it increases costs to both the health care system and patients in the U.S.,” said Joseph Babigumira, lead author of the study and assistant professor of global health at the School.

Giant cell arteritis most often affects the arteries in the head, especially those in the temples. The condition frequently causes headaches, scalp tenderness, jaw pain and vision problems. If left untreated, it can lead to stroke or blindness.

“It is estimated that nearly 950,000 individuals will be diagnosed with giant cell arteritis and 140,000 will become visually impaired because of giant cell arteritis in the U.S. between 2014 and 2050,” the researchers wrote, citing previous research.

To estimate the cost of illness among patients with the disease, researchers used a national sample of claims data from the Truven Health Analytics MarketScan databases for the years 2007-2013, as well as data from the Medicare supplemental database.

Researchers compared the health care costs of 1,293 patients recently diagnosed with giant cell arteritis to that of a control group of 6,465 enrollees who did not have the chronic disease.

The findings, published online Jan. 13 in the open-access journal Rheumatology and Therapy, showed that the “mean one-year cost for giant cell arteritis patients was $34,065 and mean one-year cost for controls was $12,890.” After adjusting for multiple variables, the difference in cost was $16,431.

What’s more, patients with giant cell arteritis spent an average of more than $5,000 in additional inpatient costs, more than $10,000 in additional outpatient costs and $660 in additional pharmacy costs.

Total health care cost associated with giant cell arteritis in the first year following diagnosis in the U.S. is higher than that of non-cystic fibrosis bronchiectasis, systemic lupus erythematosus and endometriosis, but lower than costs associated with breast cancer.

“Given the annual incidence of 18.9 giant cell arteritis cases per 100,000 population in the U.S., the first-year aggregate cost of giant cell arteritis following diagnosis is estimated to be nearly one billion dollars in the U.S.,” researchers wrote.

“Effective therapies are needed to reduce the impact of giant cell arteritis on morbidity, and have the potential to reduce the cost burden of the complications associated with the disease,” Babigumira said.

Louis Garrison, Denise Boudreau, Jennie Best and Meng Li also contributed to the study.