In a recent study published in PLOS One, researchers use Poisson regression modeling to elucidate trends in autism spectrum disorder (ASD) in Fleetwood, England. Using almost 70 years of data, the researchers demonstrated that while overall autism cases in this typical English-deprived coastal town had increased, differences between male and female autism incidences are less prominent than previously thought.
Study: Autism trends in a medium size coastal town of England. Image Credit: PeopleImages.com - Yuri A / Shutterstock.com
What is ASD?
ASD is a rare developmental disability caused by an interplay of genetic and environmental factors that lead to structural differences in the brain. ASD is characterized by difficulties in social interaction and communication, as well as restricted or repetitive behaviors and interests. Previous research estimates the global prevalence of ASD to be 0.72%, with most patients being male.
In the United Kingdom, the prevalence of ASD is higher than the global estimate at 1-1.5%. In fact, the incidence of ASD in the U.K. has been rapidly rising, with an almost eight-fold increase reported between 1998-2018.
Increased ASD awareness amongst clinicians and the general population has been postulated as the primary reason for this increase; however, anthropogenic and climatic stresses have not been ruled out.
ASD prevalence in the U.K. varies from region to region, with increased urbanization correlating with higher prevalence. However, this trend necessitates revisiting inconsistencies in the diagnostic tools and metrics used across the nation.
About the study
In the present study, researchers analyze ASD trends in small-to-medium-sized coastal towns using Fleetwood as a case study. To this end, almost 70 years of data from patients of Fleetwood primary healthcare practices were obtained between July 1952 to March 2022. Query census data from the Middle Super Output Area (MSOA) was used to estimate the annual prevalence of ASD.
The study dataset was categorized into ASD and Asperger’s syndrome. Odds ratios (ORs) were calculated for both categories to determine potential gender correlations.
Data were then analyzed within a statistical framework comprising chi-square comparisons of gender and Poisson regression assessments of the changing trends in autism reporting over the years.
Rising ASD rates in both males and females
An increasing trend of over 20-fold in ASD prevalence from 0.07 to 7.03 individuals for every 1,000 was observed in Fleetwood, especially from 2002-2022. ASD incidence in the region has increased sevenfold from 0.07 to 0.47 individuals for every 1,000 during the same time period.
Similar to global and U.K.-centric ratios, the probability of ASD was between three and 3.6 times higher for males than females in Fleetwood. One of the proposed reasons for this gender bias is the historical difficulty in screening women with the condition; however, research has not yet ruled out genetic underpinnings for this observation.
Asperger’s syndrome trends also increased over time, with its prevalence increasing from 0.04 to 1.18 patients for every 1,000 residents in the two-decade-long period. However, this data is unreliable due to limited availability and small sample sizes.
Male-to-female ratios were smaller than those observed in ASD. Increasing awareness as a consequence of public health campaigns is considered instrumental in the increasing diagnosis of these conditions and reducing discrepancies between male-female odds ratios.
Given the significance of the variable ‘time’ in our regression analyses, we suggest that the latter is to be considered as a major driver in the trends making differences between genders less significant.”
Study limitations
The small sample size was a notable limitation of the current study, as Fleetwood’s total population is approximately 30,000 individuals. In addition to the health and socio-economic concerns of the region, the study findings results may not be generalizable to even other areas in the U.K., let alone globally.
Dividing the dataset into only two classes of ASD and Asperger’s syndrome, despite the disorders representing a complex spectrum of conditions, reduces the analyses’ power to identify the drivers of gender ratios and prevalence trends.
Most importantly, due to identifiability restrictions it was not possible to associated other demographic and environmental factors that may be related to ASD diagnoses.”
Conclusions
The current study elucidated increasing trends in ASD prevalence and incidence in medium-sized coastal English towns using decades of data from Fleetwood. Poisson regression analyses of this data with time as the predictor suggest that, while the diagnosis ratio remains skewed towards the male gender, this male-female discrepancy has been reducing with time.
Both the increasing trend in ASD diagnosis and reduced gender bias has been attributed to successful public health campaigns and their consequential increased awareness of ASD among clinicians and citizens alike.
These findings provide the foundation for future research aimed at identifying the underlying mechanisms associated with ASD prevalence, risk factors, and trends. This data could help policymakers make informed decisions on apt interventions to aid individuals with ASD, many of whom remain undiagnosed to this day.
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