MONDAY, Dec. 8 (HealthDay News) -- Fewer American women and children are developing anemia, according to a new U.S. Centers for Disease Control and Prevention report.
But the researchers can't pinpoint reasons for the improvement.
The report found that rates of anemia in children dropped by more than half, from 8 percent to less than 4 percent. And among women the rates declined from nearly 11 percent to about 7 percent.
"The positive news is that anemia prevalence has gone down. Anemia has been associated with impaired cognitive development in children, and possibly impaired cognition in women," said the study's lead author, Sarah Cusick, a micronutrient specialist with the CDC in Atlanta.
"We tried to assess what possible causes of anemia might have contributed to the decline. There are many different causes of anemia -- some are nutritional, while others can be caused by inflammation. What we found was that none of those possible causes could account for the significant decline we saw in U.S. women and children. This was an unexplained decline," Cusick said.
Results of the study were published in the December issue of the American Journal of Clinical Nutrition.
Anemia is a condition in which there's a lower-than-normal number of red blood cells in the blood. Symptoms can include fatigue, chest pain and shortness of breath, according to the U.S. National Institutes of Health.
To assess the rates of anemia, Cusick and her colleagues compared two datasets from a large, nationally representative trial, the National Health and Nutritional Examination Surveys (NHANES). The first dataset included information from 1988 to 1994 and the second contained information from 1999 through 2002.
The rate of anemia in children was 8 percent for the first survey and 3.6 percent for the second. For women, the rate of anemia was 10.8 percent during the first study period and 6.9 percent during the second.
The prevalence of iron deficiency anemia didn't drop significantly for either women or children. However, folate deficiency dropped in women during the two time periods from 4.1 percent to 0.5 percent, according to the study. Data on folate deficiency anemia in children wasn't included in the study.
One of the biggest nutritional changes that occurred during the two study periods was the addition of folic acid to breads, cereals and other grain products in the United States. But, Cusick said, even the introduction of folic acid-fortified foods didn't explain the drop in anemia prevalence.
One concerning point the study raised was the disparity in anemia rates between minority women and white women. Although anemia rates declined among black and Hispanic women, the prevalence of the condition still remained much higher in these groups. Nearly one in four black women was anemic, as were nearly 9 percent of Hispanic women. This compared to 3.3 percent of white women.
"The fact that about 25 percent of black women between 20 and 49 years of age are anemic should be considered a public health crisis," Dr. Donald Mahoney Jr., a professor of pediatrics at Baylor College of Medicine in Houston, wrote in an accompanying editorial in the journal.
Both Cusick and Mahoney said access to health care may be one of the issues contributing to the higher rates among minority women. Cusick said poor nutrition may also play a role.
"It's encouraging to see that the overall prevalence of anemia is declining in women and children, though certainly, as the authors clearly imply, there are still some important gaps that require additional study and intervention," Mahoney said.
To learn more about anemia, visit the U.S. National Library of Medicine.
SOURCES: Sarah Cusick, Ph.D., micronutrient specialist, U.S. Centers for Disease Control and Prevention, Atlanta; Donald H. Mahoney Jr., M.D., professor of pediatrics, Baylor College of Medicine, and director, hemophilia/thrombosis center, Texas Children's Cancer Center and Hematology Service, Houston; December 2008, American Journal of Clinical Nutrition