Every baby born in Denmark, within the first few days of life, receives a unique, 10-digit identification number. The baby’s name and number become a part of the Danish Medical Birth Registry, a comprehensive electronic record of the birth details — from birth weight and length to parents’ smoking habits — established in 1968.

“[The identification number] is nearly tattooed on your forehead, you cannot get rid of it,” says Poul Thorsen, associate professor of epidemiology at the University of Aarhus. “It’s fixed to you and anything you do for the rest of your life.”

As babies grow older, more than 200 linked electronic registries keep track of their every encounter with the nationalized medical establishment, recording every condition diagnosed and every drug prescribed. In recent years, these massive data collections have played a pivotal role in epidemiological medical research, particularly in identifying risk factors for complex psychiatric diseases such as autism and schizophrenia.

One collection, the Danish Psychiatric Central Register (DPCR), has tracked every person admitted to a psychiatric hospital since 1938, and nearly every person diagnosed with autism since 1995. Since 1982, the Statens Serum Institut in Copenhagen has stored dried blood spot samples pricked from the heel of every newborn. This biobank, called the Danish Newborn Screening Biobank (NBS-Biobank), holds more than 2 million samples, with roughly 70,000 more added each year.

Danish citizens, through their physicians, have the right to access these collections for health reasons whenever they need. For instance, doctors initially draw the blood for the NBS-Biobank so that babies can be tested for phenylketonuria (PKU), a deadly metabolic disease that can be prevented by diet.

Together, these Danish registries and biobanks hold medical information about all 5.5 million living Danish citizens, as well as many millions of others who have died since the registries’ conception. For autism, with its relatively low prevalence of about 1 in 150, the huge numbers may prove to be a godsend.

Most of the data from the registries is managed by Denmark’s National Board of Health, based in Copenhagen. For interested researchers, access to the anonymized data requires approval from the Danish Data Protection Agency, the National Board of Health and various ethical committees, depending on the type of research proposed.

For instance, researchers from Aarhus University Hospital analyzed registry samples from 444 children with autism and 444 controls and reported on 13 January that, contrary to indications from previous studies, the glutamate decarboxylase gene 1 on chromosome 2 is not associated with autism.

In December, drawing from more than 400,000 Danish registry samples, an international group of epidemiologists found that the apparent increase in autism prevalence from 1994 to 1999 is partly due to a drop in the age at which the children were diagnosed.

These registries are “a great resource for the world,” says Thorsen, an author on both reports and on dozens of other autism studies that used registry data.

…Read the rest of my article at SFARI