BAKERSFIELD, Calif. -- More than two million Americans are living with celiac disease -- an immune system reaction to gluten in the diet that can cause abdominal pain, anemia, and weight loss.

And new research has found that the frequency of celiac disease may be increasing in the United States.

Doctors at the Mayo Clinic compared blood samples taken from young adults at Warren Air Force Base in Wyoming between 1948 and 1954 to blood samples from adults living in Minnesota today. They tested all the samples for an antibody produced by people with celiac disease.

Results showed that the disorder was four times more common among adults today than it was 60 years ago.

The study also found that undiagnosed celiac disease may be especially harmful. Participants from the 1950s with celiac disease had a four times greater risk for premature death than those without the disorder.

Celiac disease runs in families, indicating that genes play a major role -- but researchers said their findings suggest that future studies need to look for environmental changes that may be contributing to the rise in cases.