Have Secular Changes in Perinatal Risk Factors Contributed to the Recent Autism Prevalence Increase? Development and Application of a Mathematical Assessment Model

National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
Annals of epidemiology (Impact Factor: 2). 12/2011; 21(12):930-45. DOI: 10.1016/j.annepidem.2011.08.009
Source: PubMed

ABSTRACT A 57% increase in the U.S. prevalence of autism spectrum disorders (ASD) for 8-year-old children born in 1994 versus 1998 was recently reported.
To quantify the possible contributions of given risk/predictive factors on the recent ASD prevalence increase, we formulated a mathematical model based on the baseline risk factor prevalence (RFP), the proportionate change in RFP (cRFP), and the magnitude of the association between the risk factor and ASD [estimated relative risk (RR)]. We applied this model to several pregnancy-related factors (preterm, very preterm, low and very low birth weight, multiple birth, cesarean delivery, breech presentation, and assisted reproductive technology use). RFP and cRFP estimates for each factor were obtained from U.S. population-based surveillance datasets. Estimated RRs were obtained from a series of systematic literature reviews.
We estimate that each risk factor examined, alone or in various combinations, accounted for a very small proportion (<1%) of the ASD increase. Additionally, hypothetical scenarios indicate RFP, cRFP, and RR all need to be sizable for a risk factor to appreciably influence ASD prevalence.
Thus, although various pregnancy factors have been found to be associated with ASDs, the contribution of many of these factors to the recently observed ASD increase is likely minimal.

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    • "ogel , 2006 ] . The reported increase in prevalence of preterm birth could be a contributing fac - tor to the increase in ASD prevalence . However , Schieve et al . reported in 2011 that perinatal risk factors ( including preterm birth ) accounted for only a very small proportion ( <1% ) of the ASD increase in children born between 1994 and 1998 [ Schieve et al . , 2011 ] ."
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    ABSTRACT: Autism Spectrum Disorder (ASD) is a serious neurodevelopmental disorder. Several previous studies have identified preterm birth as a risk factor for ASD but none has studied whether the association between gestational age and ASD has changed over time. This is a Danish population-based follow-up study including live-born singletons born in Denmark between 1980 and 2009, identified in the Danish Medical Birth Registry, a study population of 1,775,397 children. We used a Cox regression model combined with spline to study the risk for ASD by gestational age across three decades of birth cohorts. We included 19,020 children diagnosed with ASD. Across all birth year cohorts, we found that the risk of being diagnosed with ASD increased with lower gestational age (P-value: <0.01). Across all gestational weeks, we found a statistically significant higher risk estimates in birth cohort 1980 to 1989, compared to birth cohorts 1990 to 1999 and 2000 to 2009, respectively. No statistically significant difference in risk estimates was observed between birth cohort 1990 to 1999 and 2000 to 2009. The observed time trend in risk of ASD after preterm birth may reflect: (1) a change in the risk profile of persons with ASD due to the broadening of ASD diagnostic criteria over time; or (2) improved neonatal care for low GA infants, which has reduced risk of adverse outcomes like ASD in preterm children. Autism Res 2015. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.
    Autism Research 09/2015; DOI:10.1002/aur.1525 · 4.33 Impact Factor
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    • "A meta-analysis of seven retrospective epidemiologic studies, representing five different geographic locations concluded that the following factors were associated with an increased risk of ASD; low birth weight, reduced gestational age at birth, birth asphyxia, and advanced maternal age (>35 years), along with a maternal place of birth outside Europe/North America (Kolevzon et al., 2007). A further five epidemiological studies published after 2007 found similar associations (Schendel and Bhasin, 2008; Williams et al., 2008a; Buchmayer et al., 2009; Schieve et al., 2011; Guinchat et al., 2012; Lampi et al., 2012; Movsas and Paneth, 2012), with the exception of Schieve et al. (2011), who found that prematurity did not account for a significant proportion of the increase in ASD prevalence. Yet this study addressed the predictive factors associated with the recent increase in ASD prevalence, rather than ASD diagnosis per se. "
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    ABSTRACT: Autism Spectrum Disorder (ASD) is the collective term for neurodevelopmental disorders characterized by qualitative impairments in social interaction, communication, and a restricted range of activities and interests. Many countries, including Australia, have reported a dramatic increase in the number of diagnoses over the past three decades, with current prevalence of ASD at 1 in every 110 individuals (~1%). The potential role for an immune-mediated mechanism in ASD has been implicated by several studies, and some evidence suggests a potential link between prenatal infection-driven inflammation and subsequent development of ASD. Furthermore, a modest number of contemporary studies have reported a markedly increased prevalence of ASD in children born preterm, who are at highest risk of exposure to perinatal inflammation. However, the mechanisms that underpin the susceptibility to infection-driven inflammation during pregnancy and risk of preterm birth, and how these intersect with the subsequent development of ASD in the offspring, is not understood. This review aims to summarize and discuss the potential mechanisms and evidence for the role of prenatal infection on the central nervous system, and how it may increase the susceptibility for ASD pathogenesis in children born preterm.
    Frontiers in Neuroscience 07/2013; 7(7):123. DOI:10.3389/fnins.2013.00123 · 3.66 Impact Factor
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    • "For Johnson et al. Genomics and ASD example, although changes in perinatal risk factors (i.e., low birth weight, preterm, breech, multiple, and cesarean births, and use of assisted reproductive technology) have been found to be associated with ASDs, the contribution of many of these factors to the recently observed ASD increase is unknown (Schieve et al., 2011). "
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    ABSTRACT: Purpose: To present the current state of the evidence regarding translation of genetics (the study of single genes) and genomics (the study of all genes and gene-gene or gene-environment interactions) into health care of children with autism spectrum disorder (ASD). Methods: This article presents an overview of ASD as an international health challenge, the emerging science related to broad diagnostic criteria, and the role of the nurse in research, education, and practice. Findings: Much progress is being made in the understanding of genetics and genomics of ASD. Environmental factors are thought to contribute to the risk of developing ASD by interacting with a number of genes in different ways, thus suggesting causal heterogeneity. The rising identified prevalence of ASD, the changing diagnostic criteria for ASD, and the complexity of the core and associated features have made it difficult to define the ASD phenotype (observable behaviors that result from gene-environment interaction). Because early identification improves opportunities for intervention, researchers are looking for a useful biomarker to detect ASD. This search is complicated by the likelihood that there are multiple causes for multiple expressions that are defined as the autism spectrum. Conclusions: To date, genetic and genomic research on ASD have underscored the complexity of the causes of ASD indicating that there are very complex genetic processes involved that are still not well understood. Clinical Relevance: Nurses will benefit from new knowledge related to early identification, diagnosis, and implications for the family to promote early intervention. Families who have a child with ASD will require nursing support for advocacy for optimal health outcomes.
    Journal of Nursing Scholarship 01/2013; 45(1). DOI:10.1111/j.1547-5069.2012.01483.x · 1.64 Impact Factor
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