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Mom's anemia may raise schizophrenia risk in offspring
NEW YORK |
NEW YORK (Reuters Health) - Doctors have long recommended iron supplements for the support of a healthy pregnancy, but new research adds even more weight to the sage advice: By increasing her iron intake, a pregnant woman may also decrease her baby's risk of schizophrenia later in life.
Children of mothers who had been diagnosed with anemia during pregnancy, most likely due to iron deficiency, had a significantly elevated risk of developing the mental disorder, the study's lead researcher Dr. Holger Srensen of the University Hospital of Copenhagen in Demark, told Reuters Health by email.
Iron is necessary for the production of hemoglobin, a protein that distributes oxygen throughout the body. Because a pregnant woman carries an additional set of organs and tissues -- and almost 50 percent more blood -- she needs extra iron to ensure that enough oxygen gets around.
"We speculate that maternal iron deficiency may disrupt essential pathways that affect the delivery of oxygen and nutrients to the fetus," Srensen said. Earlier research has suggested that a failure to meet the iron demands of a developing brain might heighten a child's vulnerability to disorders such as schizophrenia.
To further investigate this potential link, Srensen and colleagues analyzed the psychiatric outcomes of a large group of Danish children born between 1978 and 1998 -- the biggest cohort in which the relationship has been examined. Each child was followed from age 10 until the onset of schizophrenia, death or the study's closure on December 31, 2008.
Among 1,115,752 newborns, 17,940 (1.6 percent) were exposed to anemia in the womb. A total of 3,422 -- including 41 from the exposed group -- went on to develop schizophrenia, according to the report published in the journal Schizophrenia Bulletin.
After accounting for differences between the two groups and other relevant factors, including the parents' ages and history of mental illness, exposure to anemia in the womb was associated with a 60 percent increased risk of schizophrenia in offspring during the 20 years of the study.
The researchers further concluded that 0.58 percent of schizophrenia cases (a total of about 20 diagnoses) could have been prevented had there been no cases of anemia among the mothers.
These figures may be underestimates of anemia's true impact, according to Srensen and colleagues. It is possible that some pregnant women received anemia diagnoses and treatment from general practitioners outside the hospital, and therefore outside of the Danish registry used for the study.
Schizophrenia diagnoses may have been underreported as well. Even the oldest cohort members were only followed until age 30. Rates of schizophrenia peak around age 22 or 23, noted Srensen, so the study "may have missed around 50 percent of cases with a later onset."
The researchers also lacked access to the women's precise hemoglobin levels, which prevented assessment of the relative severity of anemia.
As reported previously by Reuters Health, Dr. Alan S. Brown of Columbia University in New York and colleagues found that exposure to particularly serious cases of anemia increased an offspring's risk of schizophrenia about four-fold. "We showed that the lower the hemoglobin level, the greater the risk of schizophrenia," Brown told Reuters Health in an email. It could be that the inclusion of especially minor cases diluted anemia's effect in the new study.
Despite its unresolved relationship with schizophrenia, prevention and treatment of maternal anemia remains straightforward. "Checking for iron-deficiency anemia (or anemia from other causes), and correcting a deficit," Srensen said, "is relatively simple in a clinical setting."
SOURCE: Schizophrenia Bulletin, January 21, 2010
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