Thimerosal and the occurrence of autism: negative ecological evidence from Danish population-based data.
OBJECTIVE
It has been suggested that thimerosal, a mercury-containing preservative in vaccines, is a risk factor for the development of autism. We examined whether discontinuing the use of thimerosal-containing vaccines in Denmark led to a decrease in the incidence of autism.


METHODS
Analysis of data from the Danish Psychiatric Central Research Register recording all psychiatric admissions since 1971, and all outpatient contacts in psychiatric departments in Denmark since 1995.


METHODS
All children between 2 and 10 years old who were diagnosed with autism during the period from 1971-2000.


METHODS
Annual and age-specific incidence for first day of first recorded admission with a diagnosis of autism in children between 2 and 10 years old.


RESULTS
A total of 956 children with a male-to-female ratio of 3.5:1 had been diagnosed with autism during the period from 1971-2000. There was no trend toward an increase in the incidence of autism during that period when thimerosal was used in Denmark, up through 1990. From 1991 until 2000 the incidence increased and continued to rise after the removal of thimerosal from vaccines, including increases among children born after the discontinuation of thimerosal.


CONCLUSIONS
The discontinuation of thimerosal-containing vaccines in Denmark in 1992 was followed by an increase in the incidence of autism. Our ecological data do not support a correlation between thimerosal-containing vaccines and the incidence of autism.
Madsen
Kreesten M
KM
Danish Epidemiology Science Centre, Department of Epidemiology and Social Medicine, University of Aarhus, Denmark. kmm@dadlnet.dk
Lauritsen
Marlene B
MB
Pedersen
Carsten B
CB
Thorsen
Poul
P
Plesner
Anne-Marie
AM
Andersen
Peter H
PH
Mortensen
Preben B
PB
D001321:Autistic Disorder / Q000139:chemically induced* / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects; D012042:Registries / Q000706:statistics & numerical data; D018570:Risk Assessment; D013849:Thimerosal / Q000009:adverse effects* / Q000737:chemistry; D014612:Vaccines / Q000009:adverse effects
D011310:Preservatives, Pharmaceutical; D014612:Vaccines; D013849:Thimerosal