The Prevalence of Autism Spectrum Disorders in Toddlers: A Population Study of 2-Year-Old Swedish Children.

A recent study, The Prevalence of Autism Spectrum Disorders in Toddlers: A Population Study of 2-Year-Old Swedish Children, considers changes in prevalence in very young children and the effect of early screening:

Autism Spectrum Disorder (ASD) is more common than previously believed. ASD is increasingly diagnosed at very young ages. We report estimated ASD prevalence rates from a population study of 2-year-old children conducted in 2010 in Gothenburg, Sweden. Screening for ASD had been introduced at all child health centers at child age 21/2 years. All children with suspected ASD were referred for evaluation to one center, serving the whole city of Gothenburg. The prevalence for all 2-year-olds referred in 2010 and diagnosed with ASD was 0.80%. Corresponding rates for 2-year-olds referred to the center in 2000 and 2005 (when no population screening occurred) were 0.18 and 0.04%. Results suggest that early screening contributes to a large increase in diagnosed ASD cases.

The prevalence for this young age group in Gothenburg Sweden showed a dramatic rise: from 0.04% in the year 2000, to 0.18% in 2005 and a big jump to 0.80% in 2010.

I’m sure many things have changed in Gothenburg in the past 10 years. However, the implementation of an early screening program is cited as having the major impact, as this was in place in 2010, but not for 2005 or 2000.

For those who will undoubtedly ask: the vaccine schedule for Sweden did not change remarkably in that time period.

2007: A revised schedule is implemented from 2007, including a diphtheria-tetanus-pertussis booster at school entry (DTaP) and at school leaving (dTap), and also a lower age for the second MMR (6-8 years). The new schedule starts with children born from 2002. Children born 1995-2001 receive a single dose pertussis catch-up in form of DTaP instead of DT at 10 years.

2009: PCV7 was introduced into the national childhood vaccination programme and recommended at 3, 5 and 12 months of age to all children born from October 2008 onwards.

2010: HPV introduced into the national childhood vaccination programme on 1st January 2010.

The 2007 change doesn’t affect children 2 1/2 and under. The 2009 addition of PCV7 doesn’t affect the children in 2005, where the prevalence was over 4 times higher than in 2000. HPV doesn’t affect children aged 2 1/2. Thimerosal was removed from vaccines in Sweden in the early 1990’s, so that exposure was unchanged over the entire period. My guess is this won’t stop people from pointing to the PCV7 vaccine as the “toxic tipping point” for Swedish kids.

Call me biased. I’m going with the authors on this one and giving credit to the hard work of the screening program implemented.