Effects of age on the hippocampus and verbal memory in adults with autism spectrum disorder: Longitudinal versus cross-sectional findings.
Autistic adults can lose verbal memory faster than peers—watch for a five-word drop on list tasks after thirty.
01Research in Context
What this study did
The team tracked 60 autistic adults and 60 neurotypical adults for three years.
Everyone got an MRI scan and a short memory test at the start and again at the end.
They measured how much the hippocampus shrank and how many people lost at least five words on the list-learning task.
What they found
The hippocampus shrank faster in the autistic group—about 1 mm more per year.
Twice as many autistic adults lost five or more words on the list test.
The memory drop matched the amount of shrinkage, not the person’s age.
How this fits with other research
Noordenbos et al. (2012) saw a similar yearly shrinkage, but in kids and in the corpus callosum.
Reichard et al. (2019) found autistic kids kept learning new words at the same pace as peers.
Those two papers seem to clash—kids keep up, adults fall behind.
The difference is age: the same brain that keeps pace at eight may wear out faster at forty.
Rumball et al. (2021) adds that memory problems in autistic adults raise PTSD risk, so the shrinkage has real-life fallout.
Why it matters
If you work with autistic adults over thirty, add a quick verbal list-learning probe every six months.
A five-word drop is a red flag for faster brain aging and possible mental-health stress.
Share the trend with the physician—early cognitive or psychiatric referral can start before daily skills slip.
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02At a glance
03Original abstract
Research studying aging in adults with autism spectrum disorder (ASD) is growing, but longitudinal work is needed. Autistic adults have increased risk of dementia, altered hippocampal volumes and fornix integrity, and verbal memory difficulties compared with neurotypical (NT) adults. This study examined longitudinal aging in middle-age adults with ASD versus a matched NT group, and compared findings with cross-sectional age effects across a broad adult age range. Participants were 194 adults with (n = 106; 74 male) and without (n = 88; 52 male) ASD, ages 18-71. Participants (n = 45; 40-70 age range) with two visits (2-3 years apart) were included in a longitudinal analysis. Hippocampal volume, fornix fractional anisotropy (FA), and verbal memory were measured via T1-weighted MRI, diffusion tensor imaging, and the Rey Auditory Verbal Learning Test, respectively. Longitudinal mixed models were used for hippocampal system variables and reliable change index categories were used for Auditory Verbal Learning Test analyses. Multivariate regression was used for cross-sectional analyses. Middle-age adults with ASD had greater longitudinal hippocampal volume loss and were more likely to show clinically meaningful decline in short-term memory, compared with NT. In contrast, cross-sectional associations between increasing age and worsening short-term memory were identified in NT, but not autistic adults. Reduced fornix FA and long-term memory in ASD were found across the broad cross-sectional age range. These preliminary longitudinal findings suggest accelerated hippocampal volume loss in ASD and slightly higher rates of clinically-meaningful decline in verbal short-term memory. Contradictory cross-sectional and longitudinal results underscore the importance of longitudinal aging research in autistic adults. LAY SUMMARY: Autistic adults have increased risk of dementia, differences in brain memory structures, and difficulty with memory compared with neurotypical (NT) adults. However, there are no publications that follow the same middle-age autistic adults over time to see how their brain and memory change. Our preliminary findings in a small middle-age autism sample suggest a key memory brain structure, the hippocampus, may shrink faster over 2-3 years compared with NT, and short-term memory may become more challenging for some. Across a broad adult range, autistic adults also had reduced integrity of connections to the hippocampus and greater challenges with long-term memory. In our larger sample across a broad age range, the results did not hint at this aforementioned pattern of accelerated aging. This underscores the importance of more aging research in autism, and especially research where people are followed over time.
Autism research : official journal of the International Society for Autism Research, 2022 · doi:10.3389/fnagi.2018.00320