The UCLA-University of Utah epidemiologic survey of autism: Recurrent infections

Childhood infections and autism spectrum disorders and/or intellectual disability: a register-based cohort study

Objective

To explore the associations between childhood infections and subsequent diagnoses of autism spectrum disorder (ASD), intellectual disability (ID), and their co-occurrence.

Methods

The association between specialized care for any infection, defined by ICD-codes, and later ASD or ID was investigated in a register-based cohort of 556,732 individuals born 1987–2010, resident in Stockholm County, followed from birth to their 18th birthday or December 31, 2016. We considered as potential confounders children’s characteristics, family socioeconomic factors, obstetric complications, and parental histories of treatment for infection and psychiatric disorders in survival analyses with extended Cox regression models. Residual confounding by shared familial factors was addressed in sibling analyses using within-strata estimation in Cox regression models. Sensitivity analyses with the exclusion of congenital causes of ASD/ID and documented risk for infections were also performed.

Results

Crude estimates indicated that infections during childhood were associated with later ASD and ID with the largest risks observed for diagnoses involving ID. Inclusion of covariates, exclusion of congenital causes of ASD/ID from the population, and sibling comparisons highlighted the potential for confounding by both heritable and non-heritable factors, though risks remained in all adjusted models. In adjusted sibling comparisons, excluding congenital causes, infections were associated with later “ASD without ID” (HR 1.24, 95%CI 1.15–1.33), “ASD with ID” (1.57, 1.35–1.82), and “ID without ASD” (2.01, 1.76–2.28). Risks associated with infections varied by age at exposure and by age at diagnosis of ASD/ID.

Conclusions

Infections during childhood may contribute to a later diagnosis of ID and ASD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11689-022-09422-4.

A Systematic Review and Meta-Analysis of Immunoglobulin G Abnormalities and the Therapeutic Use of Intravenous Immunoglobulins (IVIG) in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder affecting approximately 2% of children in the United States. Growing evidence suggests that immune dysregulation is associated with ASD. One immunomodulatory treatment that has been studied in ASD is intravenous immunoglobulins (IVIG). This systematic review and meta-analysis examined the studies which assessed immunoglobulin G (IgG) concentrations and the therapeutic use of IVIG for individuals with ASD. Twelve studies that examined IgG levels suggested abnormalities in total IgG and IgG 4 subclass concentrations, with concentrations in these IgGs related to aberrant behavior and social impairments, respectively. Meta-analysis supported possible subsets of children with ASD with low total IgG and elevated IgG 4 subclass but also found significant variability among studies. A total of 27 publications reported treating individuals with ASD using IVIG, including four prospective, controlled studies (one was a double-blind, placebo-controlled study); six prospective, uncontrolled studies; 2 retrospective, controlled studies; and 15 retrospective, uncontrolled studies. In some studies, clinical improvements were observed in communication, irritability, hyperactivity, cognition, attention, social interaction, eye contact, echolalia, speech, response to commands, drowsiness, decreased activity and in some cases, the complete resolution of ASD symptoms. Several studies reported some loss of these improvements when IVIG was stopped. Meta-analysis combining the aberrant behavior checklist outcome from two studies demonstrated that IVIG treatment was significantly associated with improvements in total aberrant behavior and irritability (with large effect sizes), and hyperactivity and social withdrawal (with medium effect sizes). Several studies reported improvements in pro-inflammatory cytokines (including TNF-alpha). Six studies reported improvements in seizures with IVIG (including patients with refractory seizures), with one study reporting a worsening of seizures when IVIG was stopped. Other studies demonstrated improvements in recurrent infections, appetite, weight gain, neuropathy, dysautonomia, and gastrointestinal symptoms. Adverse events were generally limited but included headaches, vomiting, worsening behaviors, anxiety, fever, nausea, fatigue, and rash. Many studies were limited by the lack of standardized objective outcome measures. IVIG is a promising and potentially effective treatment for symptoms in individuals with ASD; further research is needed to provide solid evidence of efficacy and determine the subset of children with ASD who may best respond to this treatment as well as to investigate biomarkers which might help identify responsive candidates.

Early environmental risk factors for neurodevelopmental disorders - a systematic review of twin and sibling studies

While neurodevelopmental disorders (NDDs) are highly heritable, several environmental risk factors have also been suggested. However, the role of familial confounding is unclear. To shed more light on this, we reviewed the evidence from twin and sibling studies. A systematic review was performed on case control and cohort studies including a twin or sibling within-pair comparison of neurodevelopmental outcomes, with environmental exposures until the sixth birthday. From 7,315 screened abstracts, 140 eligible articles were identified. After adjustment for familial confounding advanced paternal age, low birth weight, birth defects, and perinatal hypoxia and respiratory stress were associated with autism spectrum disorder (ASD), and low birth weight, gestational age and family income were associated with attention-deficit/hyperactivity disorder (ADHD), categorically and dimensionally. Several previously suspected factors, including pregnancy-related factors, were deemed due to familial confounding. Most studies were conducted in North America and Scandinavia, pointing to a global research bias. Moreover, most studies focused on ASD and ADHD. This genetically informed review showed evidence for a range of environmental factors of potential casual significance in NDDs, but also points to a critical need of more genetically informed studies of good quality in the quest of the environmental causes of NDDs.

Beyond the brain: A multi-system inflammatory subtype of autism spectrum disorder

An immune-mediated subtype of autism spectrum disorder (ASD) has long been hypothesized. This article reviews evidence from family history studies of autoimmunity, immunogenetics, maternal immune activation, neuroinflammation, and systemic inflammation, which suggests immune dysfunction in ASD. Individuals with ASD have higher rates of co-morbid medical illness than the general population. Major medical co-morbidities associated with ASD are discussed by body system. Mechanisms by which FDA-approved and emerging treatments for ASD act upon the immune system are then reviewed. We conclude by proposing the hypothesis of an immune-mediated subtype of ASD which is characterized by systemic, multi-organ inflammation or immune dysregulation with shared mechanisms that drive both the behavioral and physical illnesses associated with ASD. Although gaps in evidence supporting this hypothesis remain, benefits of this conceptualization include framing future research questions that will help define a clinically meaningful subset of patients and focusing clinical interactions on early detection and treatment of high-risk medical illnesses as well as interfering behavioral signs and symptoms across the lifespan.

Patterns of contact with hospital for children with an autism spectrum disorder: a Danish register-based study

The aim of this study was to study patterns of contact with hospital for children with autism spectrum disorder (ASD) using Danish population based register data. We included all children born in Denmark from 1994 through 2002. We found that children diagnosed with ASD had an increased rate of contact with hospital, almost regardless of the cause for the hospital contact. Given the overall association between hospital contact for various causes and ASD observed in these data, hospital data should be used cautiously in future studies searching for associations between a specific disease and ASD. If the increased rate of hospital contact overall for children with ASD is not considered, then misleading over interpretations might be made of observed associations between specific diseases and ASD.

Using maternally reported data to investigate the association between early childhood infection and autism spectrum disorder: the importance of data source

BACKGROUND

Childhood infections have been found to be associated with autism spectrum disorder (ASD) in previous studies using hospital data or medical records to identify infections. We aimed to replicate these findings using maternal reports of childhood infection.

METHODS

We used the Danish National Birth Cohort consisting of 92 583 live singletons born from 1997 to 2003 in Denmark. ASD diagnoses were retrieved from the Danish Psychiatric Central Register, and a total of 945 children from the cohort were diagnosed with ASD. Data were analysed using Cox proportional hazards regression. We studied the association between ASD and maternal reports of infectious disease in the child from birth to 19 months. Furthermore, we performed secondary analyses using hospital registers to investigate the association between ASD and hospital contact in general as well as hospital contact for various infections.

RESULTS

We did not find a general association between maternal reports of infectious illness and ASD. However, hospital contact for all causes was associated with an increased risk for an ASD diagnosis. Danish children with ASD do not appear to have a general pattern of illness from infection in early life, but do have more contact with medical specialists for infections and other indications compared with the general population.

CONCLUSION

[corrected] Hospital data should be used cautiously when studying the co-morbidity of ASD; if the increased rate of hospital contact overall for children with ASD is not considered, then misleading interpretations might be made of observed associations between specific diseases and ASD.

Tympanostomy tube placement in children with autism

OBJECTIVE

To understand rate of tympanostomy tube placement (TTP) in children with autism spectrum disorder (ASD) and, if different from rate of TTP in the general population, consider reasons underlying the difference.

METHODS

Questions pertaining to TTP were asked during caregiver interview. Totally, 2080 children with ASD were characterized through collection of demographic information; medical history; and cognitive, adaptive, and behavioral assessments. Frequencies of TTP in the ASD sample were compared with general population rates according to the most recent literature. Relationships between TTP and factors that may impact the rate of TTP were investigated.

RESULTS

Totally, 15.5% of children with ASD received TTP. The older the age, the higher the rate of TTP, with 17.0% of children aged 13 to 17 years having received TTP. Chi-square results comparing general population TTP rates to the sample indicated significantly higher rates among the ASD population. Logistic regression indicated 2 significant predictors for TTP: otitis media frequency and race. Furthermore, irritability rates in children approached predictive significance (β = 0.015, p < .10).

CONCLUSIONS

The authors found that approximately 1 in 6 children with ASD underwent TTP, more than double the rate in the general population. The rate may simply be higher because physicians are swift to perform TTP in children at risk for speech delay. At this time, there exists a lack of data on the outcomes of TTP in children with ASD. More evidence is needed to understand the usefulness of TTP in children with ASD given the high rate of procedures being performed.

Development and Validation of an Inventory to Assess Mealtime Behavior Problems in Children with Autism

To date, no standardized measures have been developed to evaluate the mealtime behavior of children with autism. The Brief Autism Mealtime Behavior Inventory (BAMBI) was designed to measure mealtime behavior problems observed in children with autism. Caregivers of 40 typically developing children and 68 children with autism completed the BAMBI, the Behavioral Pediatric Feeding Assessment Scale (BPFAS), the Gilliam Autism Rating Scale (GARS), the Youth/Adolescent Questionnaire (YAQ), and a 24-hour recall interview. The BAMBI demonstrated good internal consistency, high test-retest reliability, a clear factor structure, and strong construct and criterion-related validity in the measurement of mealtime behavior problems in children with autism.

Autism and medical disorders: a review of the literature

The authors reviewed all the population studies on autism published in the English language with particular reference to the rate of medical disorders. Seven studies met criteria for inclusion in the survey. The mean of possibly autism-related medical disorders in persons with autism across these studies was 24.4%. There was a trend for higher rates of medical disorders among subjects with severe mental retardation. The evidence in respect of atypical autism was equivocal, and the overall prevalence of medical disorders in this group was similar to that found in typical autism.