The second "Denmark study". The conclusions appear to be based on lost data. SafeMinds re-ran their numbers, and found that autism rates and thimerosal levels were actually highly correlated.
Actual Question This Study Asked & Answered:
Q: Did the discontinuation of thimerosal use in vaccines in Denmark lead to a decrease in autism?
Did the study look at unvaccinated children?
Conflict of Interest (from the study itself):
"Author Affiliations: Danish Epidemiology Science Centre,Department of Epidemiology Research (Messrs Hviid, Wohlfahrt, and Dr Melbye) and Medical Department (Dr Stellfeld), Statens Serum Institut [a vaccine manufacturer], Copenhagen, Denmark."
Ability to Generalize:
None. As SafeMinds noted:
"A large percentage of diagnosed autism cases are lost from the Danish registry each year. In the ten years preceding 2000, 815 cases were lost, more than the 710 remaining in the registry in 2000. The vast majority of those lost cases would represent older children in the 2000 registry. Since the relative risk of the Hviid study is based on finding fewer older thimerosal-exposed children than younger unexposed children, the validity of their conclusion exonerating thimerosal in autism is questionable. More likely, the finding is a result of missing records rather than true lower incidence rates among the exposed group."
Scoring (Out of 40 possible points):
Asked the Right Question: 0
Ability to Generalize: 0
Conflict of Interest: 0
Post-Publication Criticism: 1
Total Score: 1
Choice Excerpt from the Study:
"As shown in Figure 2, the incidence of autism diagnosed among Swedish inpatients aged 2 to 10 years old began to increase in the mid to late 1980s, rising from a rate of 5 to 6 inpatient-diagnosed cases per 100,000 person-years before 1985 to a peak rate of 9.2/100,000 in 1993."
The authors are saying that Sweden has an autism rate of 1 in 10,000, which is SIXTY times lower than the U.S. rate of 1 in 110, which the authors donít appear to consider or discuss. Isnít anyone curious why Swedenís autism rate is SIXTY times lower that ours?
Guest Critic #1: SafeMinds
Safe Minds Analysis of Denmark Data Finds Dramatic Drop in Autism Rates After Thimerosal Removal from Vaccines, Finds Flaw in Study Appearing in JAMA, Invalidating its Conclusions
Analysis provides further substantiation of role of thimerosal in autism, sheds more light on vaccine conflicts of interest A newly released analysis of autism registry data from Denmark by Safe Minds, a non-profit autism organization, shows that the rate of autism declined from an incidence of 1 in 500 prior to 1992 to 1 in 1,500 today. This decline in the incidence of autism follows the removal of thimerosal from infant vaccines in that country in 1992. The analysis also uncovered a flaw in the methodology of Danish investigators publishing in the October issue of JAMA (Hviid et al), who utilized the same Danish registry data and concluded that autism rates in Denmark rose after thimerosal removal from vaccines.
"In our review of the Danish data we identified a flaw which resulted in a substantial loss of autism case records from the registry which essentially renders the findings from the JAMA study by Hviid and colleagues invalid", said Sallie Bernard, executive director of Safe Minds. "The registry allows 10-25% of diagnosed autism cases to be lost from its records each year. The effect of this loss is such that the records will disappear from older age groups to a much greater degree than from younger age groups in any given registry year."
The Hviid findings are based on finding fewer older children in their 2000 registry cohort than younger ones. Since the older children received thimerosal vaccines and the younger ones did not, Hviid falsely concluded that thimerosal is not a factor in autism. The Safe Minds analysis shows instead that the decline is likely due to the loss of records of older children from the registry records, rather than a true decline in autism rates in the older group.
Safe Minds reanalyzed the Denmark registry data and used an alternative method to avoid the record removal bias. The analysis looked at same-age children - 5-9 year olds - but from different registry years: 1992, when all of the children received thimerosal-containing vaccines, and 2002, when none of the children received vaccines with thimerosal. After adjusting for the lack of outpatient records in the 1992 registry, the analysis found a 2.3 higher number of autism cases among the 1992 thimerosal-exposed group relative to the 2002 non-exposed group.
The analysis then determined an autism incidence rate for the non-thimerosal group of 1 in 1,500, while the thimerosal-exposed group had an incidence of 1 in 500, a 3-fold increase. The higher figure is comparable to the 1 in 500 incidence level for core autism recently found in England and the 1 in 250 incidence level recently calculated for the US. The thimerosal exposure level and timing in pre-1992 Denmark was comparable to that in England, while that for the US was somewhat more aggressive.
The Safe Minds analysis also revealed how small shifts in study design using the Denmark data can result in large changes to the results. The volatility stems from the many changes that the data set has gone through in the past decade. This makes the data set especially prone to possible bias.
"In the Hviid study in JAMA we can clearly see how the data was misinterpreted so a conclusion could be drawn to clear thimerosal from any role in autism," said Lyn Redwood, president of Safe Minds. "This misinterpretation is not surprising given the authors' employment with the manufacturer and promoter of vaccines in Denmark, Statens Serum Institut. This conflict of interest should have been stated by JAMA."
Safe Minds is calling for a complete analysis of the Denmark autism registry data set by independent, unbiased epidemiologists who have no involvement in vaccine development, production, promotion, or administration.
Click HERE fo Safe Minds analysis.
Guest Critic #2: Bernard Rimland, Autism Research Institute
To the Editor: In their article on the association between thimerosal-containing vaccines and autism, Dr Hviid and colleagues1 acknowledged their affiliations with Statens Serum Institut, Copenhagen, Denmark, but did not disclose that the institute is a for-profit, state-owned enterprise with roughly $120 million in annual revenue. According to its 2002 Annual Report,2 vaccines represent approximately one half of Statens Serum Institut's revenues and more than 80% of its profits. Furthermore, Statens Serum Institut manufactured the now discontinued monocomponent pertussis vaccine that contained thimerosal under investigation in their study. They were also the providers of diphtheria and tetanus components of a major thimerosal-containing diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP) vaccine sold in the United States.3
Bernard Rimland, PhD
Autism Research Institute
San Diego, Calif