Neonatal Jaundice Linked to Autism, Is Vitamin D the Missing Link?
Jaundice found in full-term neonates may suggest a higher risk of a late diagnosis of psychological disorder like autism, a new Danish study published in the Nov 2010 issue of Pediatrics suggests.
By definition, neonates are babies younger than 4 weeks.
The study led by Rikke Damkjær Maimburg, PhD, of Aarhus University in Denmark, and colleagues shows jaundiced newborns were 87 percent more likely to develop a psychological disorder than neonates without jaundice.
The study also shows those born at term with jaundice were 56 percent more likely to be diagnosed with autism than those without jaundice.
An early case-control study by the authors has already found neonatal jaundice associated with afourfold increased risk of autism.
For the current study, the researchers examined data from 733,826 children born between 1994 and 2004 and registered in the Danish Medical Birth Register.
They identified 35,766 children with neonatal jaundice and 1,721 diagnosed with a disorder of psychological development during childhood.
Interesting observations include the following:
1) Jaundice was more commonly found among boys, infants born preterm, infants with congenital malformations and low-birth-weight babies;
2) Babies born between Oct and March were 97 percent more likely than other babies to develop autism;
3) Mothers who had given birth before were 129 percent more likely to have an autistic child;
The researchers explained that babies born between Oct and March, or during the winter, were less likely to be exposed to daylight, which would otherwise help break down bilirubin, which causes jaundice.
They also explained why mothers who had given birth before were more likely to have an austic child - their children were likely sent home early and did not receive timely health care which would have quickly treated jaundice, thus minimizing the threat from bilirubn, which can lead to brain injury.
Biliburin is a natural metabolite subject to the detoxifying process in the liver. Newborns who do not have the capability of breaking down the chemical can experience jaundice.
So what causes high levels of biliburin in the blood of neonates? The likely cause is vitamin Ddeficiency. Exposure of neonates to daylight has been known to help jaundice. And exposure to daylight leads to production of vitamin D, thus increasing serum levels of this nutrient.
Prenatal vitamin D deficiency has been found associated with increased risk of autism, according to Dr. John Cannell, a vitamin D expert and director of the Vitamin D Council, who first proposed that prenatal vitamin D deficiency may be one of the causes of autism.
Dr. Cannell published his vitamin D and autism theory in 2008 in Med Hypotheses; his assertion is based on the following evidence:
1) Animal studies show that severe vitamin D deficiency during gestation led to dysregulation of dozens of proteins involved in brain development – additionally, rat pups born to vitamin D deficient mothers tended to have increased brain size and enlarged ventricles and other abnormalities similar to those found in autistic children.
2) Children with Williams Syndrome tend to have greatly elevated calcitriol levels in early infancy and they usually have phenotypes that are the opposite of autism.
3) Children with rickets associated with vitamin D deficiency experience symptoms that can be treated with high doses of vitamin D.
4) Estrogen and testosterone have different effects on vitamin D's metabolism, which explains why boys are more likely than girls to suffer autism. (The current study found boys were more likely to have jaundice.)
5) Calcitriol, a metabolite of vitamin D, down-regulates production of inflammatory cytokines, which are associated with autism, in the brain.
6) Eating fish containing vitamin D during pregnancy reduces autistic symptoms in children.
7) Autism is more likely found in areas exposed to less ultraviolet rays due to latitudes, urban constructions, and air pollution all of which can increase vitamin D deficiency. Autism is also more likely found in dark-skinned people who are very likely vitamin D deficient.
Maimburg's study suggests that neonatal vitamin D deficiency could be responsible for some cases of neonatal jaundice and autism. But the results of the study could also mean that prenatal vitamin D deficiency leads to an increase in the risk of autism in children with neonatal jaundice because babies who are vitamin D deficient may likely have experienced prenatal Vitamin D deficiency.
Dr. Cannell suggests that pregnant women take 5,000 IU of vitamin D per day.
Women who have neonates with jaundice should expose their to daylight to eliminate bilirubin quickly so it will not harm their infant’s brains.
David Liu and editing by Rachel Stockton