Sickle cell anemia may not be as well-known as, say, malaria, tuberculosis or AIDS. But every year, hundreds of thousands of babies around the world are born with this inherited blood disorder. And the numbers are expected to climb.
The number of sickle cell anemia cases is expected to increase about 30 percent globally by 2050, scientists said Tuesday in the journal PLOS Medicine. Countries in sub-Saharan Africa, where the disease is most common, will be the hardest hit.
A child gets sickle cell anemia by inheriting two copies of a defective gene, one from each parent. The mutations cause red blood cells to collapse and form a crescent moon-like shape. These so-called sickle cells clump together and can't carry oxygen throughout the body.
"Because the red blood cells are sickling, they cause blockages of blood vessels all across the body," says Fred Piel, an evolutionary biologist at the University of Oxford, who led the study. The lack of oxygen and blood flow causes chronic pain and makes patients more susceptible to many infections.
In developed countries, like the U.S., babies are routinely screened for the disorder, and with the right care they can live well into adulthood. But the vast majority of kids in developing countries don't get diagnosed or treated for sickle cell anemia. "Up to 90 percent of these children will die in the first five years of their life," Piel says. The World Health Organization has long recognized the importance of sickle cell anemia as a global health issue. In 2006, the World Health Assembly called on countries to tackle the disease.
To get a handle on the global scale of the problem, Piel and his colleagues used population data and information about the frequency of the sickle cell gene within different populations.
"We estimate that it's about 300,000 births affected with sickle cell anemia per year," Piel says. He reported those numbers in a study earlier this year in the journal Lancet.
In the latest study, Piel calculated how that number will change in the future. To do that, he used estimates in population growth from the United Nations. Piel and his colleagues project that there will be about 400,000 babies born each year with sickle cell anemia by 2050.
The two countries hardest hit will be Nigeria and the Democratic Republic of Congo, Piel says. Both countries already have high numbers of sickle cell cases. In Nigeria, an estimated 91,000 babies are born with the disorder each year. In the Congo, it's about 40,000. By 2050, those numbers are expected to rise to nearly about 140,000 and 45,000, respectively.
But other, less populous countries won't be spared either. As more people from poorer countries migrate to developed countries, the cases of the disease will increase globally.
There's no cure for sickle cell anemia. But screening newborn babies, followed by vaccines and antibiotics, can prevent deadly complications, Piel says. Many countries, however, don't have the resources to do such screening or provide the necessary lifelong care needed to keep people with sickle cell anemia healthy.
"In the long term you have to find other ways to reduce the number of children affected before birth," Piel says. For instance, genetic counseling for parents who carry the sickle cell gene could help reduce the number of babies who inherit the disorder, he says.
DAVID GREENE, HOST:
It's MORNING EDITION from NPR News. I'm David Greene.
RENEE MONTAGNE, HOST:
And I'm Renee Montagne. Every year hundreds of thousands of babies all over the world are born with sickle cell anemia. It's an inherited disorder that, without treatment, is usually fatal early in life. And a study out this week finds the disease will become more common in the coming decades. As NPR's Rhitu Chatterjee reports, global health experts hope that knowledge will raise awareness about sickle cell anemia, especially in developing countries.
RHITU CHATTERJEE, BYLINE: Patients with the disease have red blood cells that are bent, like sickles. It's easy to see them under a microscope. These misshapen blood cells clog up blood vessels and prevent oxygen from reaching different parts of the body. Patricia Kavanagh is a pediatrician at Boston Medical Center and an expert on sickle cell disease.
PATRICIA KAVANAGH: The hallmark of this disease is severe pain, often requiring IV opioids to control it. And this is something that will continue throughout their life.
CHATTERJEE: Here in the United States, the disease is increasingly treated with a drug called hydroxyurea that boosts the body's ability to create normal shaped blood cells. Today about 90,000 to 100,000 people in this country have sickle cell anemia. And newborns have been routinely screened for the disorder since the late 1980s. Babies that test positive are treated with simple, inexpensive measures like penicillin to ward off potential infections.
KAVANAGH: Before we started using penicillin in all these babies, they often would die of overwhelming infection, often before their fifth birthday.
CHATTERJEE: But in tropical regions of the world, the vast majority of babies born with sickle cell anemia still die as infants. That's because most developing countries aren't aware of how widespread the disorder is. A few months ago, Fred Piel, an epidemiologist at the University of Oxford published the first global estimates.
FRED PIEL: We estimate that it's about 300,000 births affected by sickle cell anemia per year.
CHATTERJEE: Now, in this new study in the journal PLOS Medicine, Piel reports that the number of newborns with the disease will grow rapidly.
PIEL: We projected it would be about 400,000 by 2050.
CHATTERJEE: Global health researchers say the study could make a big difference in countries like India, Nigeria and the Democratic Republic of Congo where the numbers are among the highest. David Osrin is a pediatrician at the University College of London.
DAVID OSRIN: I think the paper's important because the first thing to do in situations like this is to put the disease on to the radar.
CHATTERJEE: He says that's the first step towards developing programs to identify and treat the disease.
OSRIN: Now to do this, you need some kind of screening program. And the likelihood of being able to implement this in the short term is quite limited. But I think it should be something we try to work towards.
CHATTERJEE: He says screening is worthwhile because it's not hard to immediately save lives. Once you identify affected babies, you can start them on antibiotics. And Patricia Kavanagh, the sickle cell expert at Boston Medical Center says the drug that boosts normal blood cells is a realistic treatment option for developing countries.
KAVANAGH: It's a generic drug, quite cheap.
CHATTERJEE: Kavanagh says all this should help persuade governments that they should add sickle cell anemia to the list of diseases that need resources. She says TB, malaria, HIV are indeed important.
KAVANAGH: But please put sickle cell disease on your radar as well when you design your public health interventions.
CHATTERJEE: Rhitu Chatterjee, NPR News.
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