Academic journal article Issues in Law & Medicine

Sociological Environmental Causes Are Insufficient to Explain Autism Changepoints of Incidence

Academic journal article Issues in Law & Medicine

Sociological Environmental Causes Are Insufficient to Explain Autism Changepoints of Incidence

Article excerpt

In the U.S. and many other countries, autism spectrum disorder prevalence has been increasing over the past three decades.'1,2,3,4,5,6,7,8,9,10' Recent publications suggest that some portion of the rise is due to sociologie factors (improved detection, increased awareness, increased services and funding), while another portion must be explained by biologic factors.11,2,4,11421 Recently, the Environmental Protection Agency (EPA) published a study that calculated changepoint years in the cumulative incidence of autistic disorder (AD), a more diagnostically stable subset of autism spectrum disorders.1131

Changepoint analysis assumes that time series data can be fit with multiple lines with significantly different slopes; the "changepoint" is the point where the slope changes from one value to another value. Changepoint analyses have been used to detect ecosystem response to environmental changes, and resulting estimated thresholds have been used as basis for setting environmental policy.114' For example, changepoint analysis led to the measurement of the phosphorus threshold from agricultural runoff that resulted in ecological imbalances in the Everglades.115' These types of analyses are instrumental in setting the EPAs national nutrient policy.'14' The EPAs autism study concluded that for California, Denmark, and combined worldwide autistic disorder data, there is a changepoint near birth year 1988. Their analysis demonstrates that AD was diagnosed at a higher rate in children born after 1988. Their analysis also indicates that there should be a universal environmental, sociologie or physiologic factor (prenatal or postnatal), whose introduction or change significantly affected children born in 1988 or later.

Many studies have been published that have tried to measure the effects of sociologie factors on autism rates. The impact of diagnostic substitution has been measured using California data,'9' selected U.S. data,116' as well as Canadian data." '1 However, there has been no consensus among these studies about the effect of diagnostic substitution. None of these studies has attempted to calculate changepoints for these sociologie factors. Other sociologie factors that have been considered include age at diagnosis,'11,12,18' proximity to other autistic children,"9' and legislative approval of special autism sendees.'4' One study, using CA data, has suggested that as much as 12% of the CA autism rate could be due to earlier age of diagnosis."11 Another study, using CA data for birth cohorts born after 2000, recently concluded that 4% of autism diagnoses may be linked to physical proximity to another family whose child has been diagnosed with autism."9' Regrettably, this study did not distinguish between purely social effects, such as communication, or the presence of some shared environmental factor due to physical proximity. A different study, using West Australian data, published that increased autism diagnosis rates in younger children can be correlated to the approval of special services for younger autistic children, as well as to the occasion of a meeting of professionals that discussed various criteria to be used for autism diagnosis.112' Unfortunately, this publication did not mention timing of the actual disbursement of newly approved services nor did the authors include information about when the agreed upon autism diagnostic criteria was published or disseminated.

Based on the 2010 EPA changepoint publication, we have examined the potential impact of various sociologie and environmental factors proposed to be responsible for the current autism rates. Because of the known difficulties with autism ascertainment, 120,211 no attempt is made in this work to quantify these sociologie factors relative to autism trends. Rather, we have focused on the question of whether changepoints can be identified for these sociologie factors and whether any identifiable changepoints can be temporally associated with autism disorder changepoints. …

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