FRIDAY, Dec. 2 (HealthDay News) -- Children with sickle cell disease, an inherited blood disorder, who also have high blood pressure and/or anemia are at increased risk for so-called "silent strokes," according to a new study.

Silent strokes, which cause no symptoms, "are typically seen in older adults, and these findings give us additional insight into why they tend to occur so often in children with sickle cell disease," senior study investigator Dr. James Casella, director of hematology at Johns Hopkins Children's Center, said in a center news release.

Casella and his colleagues performed MRI brain scans on 814 children with sickle cell disease, aged 5 to 15, and found that 31 percent of them had suffered silent strokes. None of the children had a history of strokes or seizures, and none showed any signs of stroke at the time of the study.

After examining the children's medical histories, the researchers concluded that anemia and high blood pressure individually increased the risk of silent stroke in the study participants, but the combination of the two carried the highest risk.

Among these sickle cell patients, those with the highest systolic blood pressure (the top number in their blood pressure reading) was above 113 and the lowest hemoglobin (below 7.6 grams per deciliter) had a nearly four times greater risk of silent stroke than those with the lowest blood pressure and highest hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen. Anemia is defined by low levels of hemoglobin.

Compared to children with the lowest blood pressure readings, those with the highest blood pressure had a 1.7 times greater risk of silent stroke. And the risk was more than doubled for kids with the lowest hemoglobin levels versus kids with the highest hemoglobin levels, the investigators found.

The researchers said their findings highlight the need to identify children with sickle cell disease who have early signs of anemia and high blood pressure, both of which are modifiable risk factors. The findings may also lead to new treatments for sickle cell disease.

The study was published online Nov. 17 in the journal Blood.

While extremely rare in children overall, stroke is a common complication in children with sickle cell disease. Nearly 100,000 people in the United States have sickle cell disease. The disease, inherited from both parents, causes red blood cells to take the shape of crescents or sickles, and results in less oxygen being delivered to the body's tissues. These fragile cells can interrupt blood flow when they get stuck in small blood vessels. Patients with sickle cell disease require ongoing treatment, according to the U.S. National Institutes of Health, which funded the study.

More information

The Nemours Foundation has more about sickle cell disease.