A longitudinal study on cognitive aging in autism

Cognitive and brain morphological deviations in middle-to-old aged autistic adults: A systematic review and meta-analysis

Cognitive challenges and brain structure variations are common in autism spectrum disorder (ASD) but are rarely explored in middle-to-old aged autistic adults. Cognitive deficits that overlap between young autistic individuals and elderlies with dementia raise an important question: does compromised cognitive ability and brain structure during early development drive autistic adults to be more vulnerable to pathological aging conditions, or does it protect them from further decline? To answer this question, we have synthesized current theoretical models of aging in ASD and conducted a systematic literature review (Jan 1, 1980 - Feb 29, 2024) and meta-analysis to summarize empirical studies on cognitive and brain deviations in middle-to-old aged autistic adults. We explored findings that support different aging theories in ASD and addressed study limitations and future directions. This review sheds light on the poorly understood consequences of aging question raised by the autism community to pave the way for future studies to identify sensitive and reliable measures that best predict the onset, progression, and prognosis of pathological aging in ASD.

Memory strategies in autistic and older adults

Memory strategies in autistic adults seem to mimic strategies at older age, as both younger autistic and older non-autistic individuals use fewer semantic features in visual memory tasks. Therefore, the current study aims to investigate whether early differences in memory strategies lead to altered age-related effects in autism, particularly whether initial difficulties in strategy use become advantageous at older age (i.e., "protective aging"). A total of 147 participants across four groups (autistic younger/older, non-autistic younger/older) completed an online assessment. This assessment included a recognition version of the Visual Patterns Test (VPT) to evaluate semantic strategy use in visual memory, the Just Noticeable Difference (JND) size task for assessing visual processing, and the Multifactorial Memory Questionnaire to evaluate subjective memory functioning and strategy use (MMQ). Unexpectedly, all groups benefited from semantic features on the VPT, although the older groups performed less accurately and slower than the younger groups. The JND Size task showed no group differences. Autistic adults rated their MMQ memory as worse than non-autistic adults, despite reporting greater strategy use. These results indicate that cognitive strategies might be more similar between younger/older and autistic/non-autistic people than previously expected, although notable discrepancies between objective and subjective measures were present. They also substantiate previously reported parallel (i.e., similar) age-related effects between autistic and non-autistic people.

Longitudinal changes in executive function in autism spectrum disorder: A systematic review and meta-analyses

Individuals with an autism spectrum disorder (ASD) diagnosis show impairment in executive function (EF). However, findings are mixed regarding differences in the age effect on EF between autistic individuals and persons with typical development (TD). Questions remain regarding whether the age-related trajectories of EF in ASD are the same as or different from those in TD. To bridge this knowledge gap, we conducted a systematic review and meta-analyses of longitudinal studies that compared age-related changes in EF between ASD and TD groups (preregistration: osf.io/j5764). A literature search was conducted using PubMed, PsycINFO, and Web of Science on January 29, 2024. After screening by two independent reviewers, 14 longitudinal studies were included. Random-effects meta-analyses of studies involving a maximum total of 518 autistic and 3558 TD children and adolescents (mean baseline ages: 5.7-12.0 years) showed that ASD had significantly poorer EF than TD at both baseline and follow-up. However, there was no significant group difference in the age-related change in EF across domains, including working memory, inhibition, shifting, and planning. Robust Bayesian meta-analyses also provided substantial evidence in favor of the null hypothesis that ASD and TD groups showed similar changes over time for most EF processes. Limitations of the literature included the limited number of longitudinal studies and a narrow range of developmental stages and EF constructs analyzed across studies. Altogether, these findings suggest that autistic children and adolescents generally can improve in EF over time similarly to their neurotypical peers. This has important implications for parents and educators, encouraging appropriate EF training and intervention for autistic children and adolescents at an early stage.

Aging Well and Autism: A Narrative Review and Recommendations for Future Research

With autism first recognized in the 1940s, the early cohorts of autistic children are beginning to enter older adulthood. Little is known about the experiences and outcomes of autistic older adults. In the general population, "successful aging" is a dominant model among gerontologists and is used to evaluate outcomes in older adulthood. This narrative review aims to provide a framework for understanding and supporting successful aging in older autistic adults. Using Fernández-Ballesteros' four-domain model of "aging well" we review knowledge on aging and autism by examining outcomes in health and functioning, cognitive and physical functioning, positive affect and control, and social participation and engagement. Findings indicate that outcomes in autistic older adults are generally poor, marked by increased medical conditions, low adaptive skills, elevated risk of cognitive decline, limited physical activity, high rates of mental health conditions, low quality of life, and reduced social or community participation. Patterns of challenges are similar across cognitive abilities and profiles of autistic traits. Challenges and next steps in aging and autism research are identified, and future directions for the field are discussed.

Associations between atypical intracortical myelin content and neuropsychological functions in middle to older aged adults with ASD

INTRODUCTION

In vivo myeloarchitectonic mapping based on Magnetic Resonance Imaging (MRI) provides a unique view of gray matter myelin content and offers information complementary to other morphological indices commonly employed in studies of autism spectrum disorder (ASD). The current study sought to determine if intracortical myelin content (MC) and its age-related trajectories differ between middle aged to older adults with ASD and age-matched typical comparison participants.

METHODS

Data from 30 individuals with ASD and 36 age-matched typical comparison participants aged 40-70 years were analyzed. Given substantial heterogeneity in both etiology and outcomes in ASD, we utilized both group-level and subject-level analysis approaches to test for signs of atypical intracortical MC as estimated by T1w/T2w ratio.

RESULTS

Group-level analyses showed no significant differences in average T1w/T2w ratio or its associations with age between groups, but revealed significant positive main effects of age bilaterally, with T1w/T2w ratio increasing with age across much of the cortex. In subject-level analyses, participants were classified into subgroups based on presence or absence of clusters of aberrant T1w/T2w ratio, and lower neuropsychological function was observed in the ASD subgroup with atypically high T1w/T2w ratio in spatially heterogeneous cortical regions. These differences were observed across several neuropsychological domains, including overall intellectual functioning, processing speed, and aspects of executive function.

CONCLUSIONS

The group-level and subject-level approaches employed here demonstrate the value of examining inter-individual variability and provide important preliminary insights into relationships between brain structure and cognition in the second half of the lifespan in ASD, suggesting shared factors contributing to atypical intracortical myelin content and poorer cognitive outcomes for a subset of middle aged to older autistic adults. These atypicalities likely reflect diverse histories of neurodevelopmental deficits, and possible compensatory changes, compounded by processes of aging, and may serve as useful markers of vulnerability to further cognitive decline in older adults with ASD.

Age, not autism, influences multisensory integration of speech stimuli among adults in a McGurk/MacDonald paradigm

Differences between autistic and non-autistic individuals in perception of the temporal relationships between sights and sounds are theorized to underlie difficulties in integrating relevant sensory information. These, in turn, are thought to contribute to problems with speech perception and higher level social behaviour. However, the literature establishing this connection often involves limited sample sizes and focuses almost entirely on children. To determine whether these differences persist into adulthood, we compared 496 autistic and 373 non-autistic adults (aged 17 to 75 years). Participants completed an online version of the McGurk/MacDonald paradigm, a multisensory illusion indicative of the ability to integrate audiovisual speech stimuli. Audiovisual asynchrony was manipulated, and participants responded both to the syllable they perceived (revealing their susceptibility to the illusion) and to whether or not the audio and video were synchronized (allowing insight into temporal processing). In contrast with prior research with smaller, younger samples, we detected no evidence of impaired temporal or multisensory processing in autistic adults. Instead, we found that in both groups, multisensory integration correlated strongly with age. This contradicts prior presumptions that differences in multisensory perception persist and even increase in magnitude over the lifespan of autistic individuals. It also suggests that the compensatory role multisensory integration may play as the individual senses decline with age is intact. These findings challenge existing theories and provide an optimistic perspective on autistic development. They also underline the importance of expanding autism research to better reflect the age range of the autistic population.

Increased anticholinergic medication use in middle-aged and older autistic adults and its associations with self-reported memory difficulties and cognitive decline

Many commonly used prescription and over-the-counter medicines have potent anticholinergic (AC) effects. Among older adults, AC medications are associated with cognitive impairment and risk for cognitive disorders, including Alzheimer's disease. Collectively, the impact of AC medications is known as anticholinergic cognitive burden (ACB). Because of the high rates of co-occurring medical and psychiatric conditions, autistic adults may have high AC exposure and, thus, may experience elevated ACB. However, no research has characterized AC exposure or examined its associations with cognitive outcomes in autistic adults. Autistic adults (40-83 years) recruited via Simons Powering Autism Research's (SPARK) Research Match service self-reported their medication use (N = 415) and memory complaints (N = 382) at Time (T)1. At T2, 2 years later, a subset of T1 participants (N = 197) self-reported on decline in cognition. Medications were coded using two scales of AC potency. A high proportion (48.2%-62.9%, depending upon the AC potency scale) of autistic adults reported taking at least one medication with AC effects, and 20.5% to 26.5% of autistic adults reported clinically-relevant levels of AC medication (potency ≥3). After controlling for birth-sex, and age, hierarchical linear regression models showed total ACB scores and AC potency values of ≥3 predicted greater memory complaints. Logistic regression models showed that AC medicines at T1 were associated with self-reported cognitive decline at follow-up 2 years later. Understanding AC medications-including potentially earlier AC polypharmacy-and their impacts on cognition (e.g., dementia risk) in autistic adults is warranted.

The Autism Constellation and Neurodiversity: Long-Term and Adult Outcomes in Autism Spectrum Disorder

Research on autistic adults suggests significant heterogeneity in outcomes. A significant proportion of individuals struggle with intellectual disability and limited communication skills. Of the 67% who have age-appropriate cognitive skills, around half are expected to attain a college education, and 25% are likely to hold a full-time job. Outcomes have been improving over time, in part because of earlier diagnosis and earlier intervention. Indeed, an estimated 10% to 20% are expected to lose all symptoms of autism by adolescence.

When mind and measurement diverge; the interplay between subjective cognitive complaints (SCCs), objective cognition, age, and depression in autistic adults

While the increased incidence of dementia and subjective cognitive complaints (SCCs) suggests that autistic adults may face cognitive challenges at older age, the extent to which SCCs predict (future) cognitive functioning remains uncertain. This uncertainty is complicated by associations with variables like depression. The current study aims to unravel the interplay of age, depression, cognitive performance, and SCCs in autism. Using a large cross-sectional cohort of autistic (n=202) and non-autistic adults (n=247), we analyzed associations of SCCs with age, depression, and cognitive performance across three domains (visual memory, verbal memory, and fluency). Results showed a strong significant association between depression and SCCs in both autistic and non-autistic adults. Cognitive performance was not significantly associated with SCCs, except for a (modest) association between visual memory performance and SCCs in autistic adults only. Follow-up regression tree analysis indicated that depression and being autistic were considerably more predictive of SCCs than objective cognitive performance. Age nor sex was significantly associated with SCCs. These findings indicate that self-reported cognitive functioning does not equal cognitive performance, and should be interpreted with care, especially in individuals with high rates of depression. Longitudinal investigations are needed to understand SCCs' role in dementia and cognitive health in autism.

Prepotent response inhibition in autism: Not an inhibitory deficit?

Research outcomes on prepotent response inhibition in neurodevelopmental conditions during adulthood seem inconsistent, especially in autism. To gain further insight in these inconsistencies, the current study investigates inhibitory performance, as well as task strategies such as adaptive behavior during inhibitory tasks in autistic adults. As Attention-Deficit/Hyperactivity Disorder (ADHD) is often co-occurring in autism and associated with differences in both inhibition and adaptation, the role of ADHD symptoms is explored. Additionally, prior research is extended to middle- and late-adulthood, and the role of cognitive aging is assessed. Hundred-and-five autistic adults and 139 non-autistic adults (age: 20-80 yrs) were compared on a Go-NoGo task. No significant group differences in inhibitory difficulties (commission errors) or adaptation (post error slowing) were observed, and both did not relate significantly to ADHD symptoms. However, when controlling for reaction time autistic individuals made significantly more inhibitory errors than non-autistic individuals, yet the effect size was modest (Cohen's d = .27). Exploratory analyses showed that adaption significantly related to inhibition in non-autistic individuals only, possibly hinting at altered adaptive behavior during inhibitory tasks in autistic adults. ADHD symptoms related to response variability in the autism group only. Furthermore, task strategy changed with older age in both groups, with slower and more cautious responses at older age. Taken together, although minor differences may exist, autistic and non-autistic people show largely similar patterns of inhibitory behavior throughout adulthood. Differences in task timing and strategy seem relevant for future longitudinal studies on cognitive aging across neurodevelopmental conditions.

Neural reinstatement of context memory in adults with autism spectrum disorder

Autism spectrum disorder (ASD) is associated with episodic memory impairment. However, episodic memories include a variety of contextual details, and it is difficult to solely rely on behavioral data to assess how specifically (i.e. event-specific reinstatement) an event is remembered. We applied encoding-retrieval representational similarity (ERS) analysis to EEG data to assess event-specific ERS for object-context associations in a sample of 34 adults (17 with, 17 without ASD). Participants studied objects presented alongside 2 contextual features: scene/color, and attention was directed toward one object-context relationship. At retrieval, memory was assessed for the object and both contexts. Behavioral results revealed no group differences in item or context memory performance. ERS results revealed group temporal differences in reinstatement. Results may indicate differences in both encoding (i.e. fewer perceptual details) and retrieval (i.e. ineffectively skipping through memory fragments) in ASD and should be further investigated in studies modulating the perceptual detail required for memory decisions. Results highlight the utility of ERS as a methodology used to evaluate episodic reinstatement even in the absence of behavioral differences in memory performance.