What's Going on? The Question of Time Trends in Autism

Abstract

Increases in the reported prevalence of autism and autistic spectrum disorders in recent years have fueled concern over possible environmental causes. The author reviews the available survey literature and finds evidence of large increases in prevalence in both the United States and the United Kingdom that cannot be explained by changes in diagnostic criteria or improvements in case ascertainment. Incomplete ascertainment of autism cases in young child populations is the largest source of predictable bias in prevalence surveys; however, this bias has, if anything, worked against the detection of an upward trend in recent surveys. Comparison of autism rates by year of birth for specific geographies provides the strongest basis for trend assessment. Such comparisons show large recent increases in rates of autism and autistic spectrum disorders in both the U.S. and the U.K. Reported rates of autism in the United States increased from <3 per 10,000 children in the 1970s to >30 per 10,000 children in the 1990s, a 10-fold increase. In the United Kingdom, autism rates rose from <10 per 10,000 in the 1980s to roughly 30 per 10,000 in the 1990s. Reported rates for the full spectrum of autistic disorders rose from the 5 to 10 per 10,000 range to the 50 to 80 per 10,000 range in the two countries. A precautionary approach suggests that the rising incidence of autism should be a matter of urgent public concern.

Use of a Teacher Nomination Strategy to Screen for Autism Spectrum Disorders in General Education Classrooms: A Pilot Study

“…The apparent increase in prevalence from previous estimates of 4-5 per 10,000 could be due to the inclusion of broader diagnostic criteria, better methods for diagnosis, or an increased awareness of the disorder (Fombonne, 2003;Yeargin-Allsopp et al, 2003). Conversely, the apparent increase could be a real phenomenon, suggesting an increase in some unidentified environmental teratogen or biological vulnerability associated with the disorder (Blaxill, 2004).…”

Rehabilitation issues in autism spectrum disorders

“…In families with one child with ASD, the prevalence rate for their sibling is 20-50-times higher than that of the population base rate [9]. Whether the reported increase is a result of actual prevalence or a combination of factors such as broadening diagnostic criteria, increased awareness and changes in relevant policy is currently unknown [6][7][8]. The precise aetiology of ASD is similarly unknown; however, it is likely multifactorial, with many agents, genetic and environmental, possibly effecting the presentation of symptoms [9][10][11].…”

“…The prevalence of ASD appears to have increased substantially over several decades and may be as high as 1 in 150 children [6][7][8]. In families with one child with ASD, the prevalence rate for their sibling is 20-50-times higher than that of the population base rate [9].…”

Efectos neurotóxicos del timerosal, a dosis de vacuna, sobre el encéfalo y el desarrollo en hámsteres de 7 días de nacidos

“…Durante los últimos años, múltiples trabajos han comunicado un extraordinario aumento de casos de desórdenes del neurodesarrollo infantil ( [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Paralelamente, una creciente minoría de médicos y científicos de todo el mundo empezó a cuestionar seriamente el uso de timerosal en la vacunación infantil, relacionándolo con el aumento de la prevalencia de diversas enfermedades del neurodesarrollo, tales como los desórdenes del espectro autista (DEA) y otros problemas de la cognición ( 12,14,15,17 ).…”

“…Paralelamente, una creciente minoría de médicos y científicos de todo el mundo empezó a cuestionar seriamente el uso de timerosal en la vacunación infantil, relacionándolo con el aumento de la prevalencia de diversas enfermedades del neurodesarrollo, tales como los desórdenes del espectro autista (DEA) y otros problemas de la cognición ( 12,14,15,17 ). Debido a ello, múltiples instituciones han realizado sendos pronunciamientos relacionados al tema ( [17][18][19][20][21][22][23][24][25][26] ).…”