Asthma seven times more likely in SCD children than in unaffected siblings
Study findings highlight importance of more frequent screening
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Children with sickle cell disease (SCD) are about seven times more likely to have asthma than their unaffected siblings, with odds increasing with age, according to a study in the U.S.
These findings highlight the importance of more frequent screening to protect the lungs and prevent asthma-related complications in children with SCD.
“Interval screening [between routine visits] should be implemented to capture cases at all ages,” researchers wrote.
The study, “Sickle Cell Disease Is an Inherent Risk for Asthma in a Sibling Comparison Study,” was published in Pediatric Blood & Cancer.
Researchers’ question: Does SCD increase risk of asthma?
SCD occurs due to the production of a faulty version of hemoglobin, the protein in red blood cells that carries oxygen. This faulty protein causes red blood cells to take on a sickle-like shape, making them more prone to breakage and blocking blood flow in small vessels, reducing the amount of oxygen delivered to tissues.
Asthma, which is thought to be driven by complex genetic and environmental interactions, causes the airways to become inflamed and narrowed, making breathing difficult. Some of its manifestations overlap with SCD symptoms, which can also cause shortness of breath.
“Asthma is a clinical diagnosis with poorly defined objective criteria,” and “it remains unclear whether a subjective physician’s diagnosis of asthma in children with SCD reflects the same constellations of clinical features observed in children without SCD,” the researchers wrote.
In addition, it remains unclear whether children with SCD have asthma as often as, or more often than, the general population.
In this study, a team of researchers in the U.S. set out to determine whether SCD increases the risk of asthma, while controlling for potential influencing factors such as genetics and the environment. They used a sibling case-control study design, meaning each child with SCD was compared with full- and half-siblings who did not have SCD.
The study included 248 children with SCD (57.7% boys), ages 2 to 18 years, and 328 unaffected siblings (55.5% males), ages 0 months to 33 years. Among the siblings, 240 were between 2 and 18 years old.
Asthma much more common in children with SCD than in their siblings
On average, children with SCD were significantly younger compared with their siblings (9.4 vs. 11.8 years). When only children ages 2 to 18 were compared between the groups, the average ages were similar, making the comparison reliable.
“Most siblings lived in the same household as their respective SCD cases,” the team wrote.
A pediatric lung specialist diagnosed asthma, and it was significantly more common in children with SCD than in their siblings (28.6% vs. 7.6%), including those ages 2 to 18, in which the frequency of asthma was 8.8%. This means asthma was more than three times more common in children with SCD than in their unaffected brothers and sisters.
Statistical analyses adjusted for age and sex showed that children with SCD were about 7.5 times as likely as their siblings to develop asthma. The odds remained higher, by nearly seven times, even when the analysis compared SCD children with siblings ages 2 to 18.
SCD “independently increases the odds for the development of asthma by up to [sevenfold],” the researchers wrote.
Within the group of children with SCD, the odds of developing asthma increased steadily with age, with each additional year of age increasing the odds by about 20%. This explains why asthma became much more common in older children and adolescents with SCD. In contrast, asthma rates in the sibling group remained stable over time.
SCD increases the risk for asthma, independent of familial and environmental factors.
Sex also influenced the odds, with boys with SCD being about twice as likely as girls with SCD to be diagnosed with asthma. Similarly, asthma in siblings ages 2-18 years was more than three times more common among boys than girls.
Children with SCD who had a family history of asthma had nearly sixfold higher odds of developing asthma compared with those without such a family history. In siblings ages 2-18 years, having a family history was linked to a more than 2.5 times higher chance of asthma.
The use of hydroxyurea, an oral medication approved to treat SCD, also increased the odds of asthma in children with SCD by more than twofold.
“SCD increases the risk for asthma, independent of familial and environmental factors,” the researchers wrote. “This effect is particularly pronounced in individuals with predisposing risk factors, also commonly observed in the general population.”
Further research is needed “to better understand how SCD contributes to asthma development and informs clinical management,” they concluded.
