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Researchers are uncovering important patterns in post-stroke cognitive impairment which suggest that factors outside stroke location contribute to the specific combination of deficits expressed in individuals.
Having a stroke leaves many stroke survivors with cognitive impairments in core domains such as memory, attention, and language. However, the pattern of cognitive problems varies dramatically across individuals, and it’s not yet well understood why this is.
Post-stroke cognitive impairment (PSCI) is the single most reported unmet care need in stroke survivors and is a key contributor to poor long-term outcomes in stroke. To improve PSCI care, it is first important to understand the specific causes of different PSCI types.
Traditionally, PSCI is thought to be a direct consequence of the specific brain areas damaged by stroke. However, recent research has identified many other factors outside of stroke location which may contribute to differences in PSCI profiles across individuals.
One key challenge is that the specific pattern of PSCI deficits varies dramatically across individuals. PSCI can affect different cognitive domains, but each domain encompasses many separate skills which may be impaired in some, but not all patients. To add to this complexity, individual PSCI deficits rarely occur in isolation.
Our research provides novel insight into why different stroke survivors exhibit different patterns of PSCI and proposes a new way of thinking about PSCI variability.
Exploring PSCI profiles
Our global, collaborative research team set out to investigate individual variability in PSCI in the largest and most detailed study to date. We recruited more than 2 000 stroke survivors across the UK, Italy, and Belgium to complete the Oxford Cognitive Screen, a standard multi-domain PSCI screening tool.
We used this data to group participants who had similar patterns of cognitive impairment into different ‘PSCI Profiles’, and to identify factors which determined individual’s PSCI profiles.
We identified 13 different PSCI profiles in stroke survivors. Some of these patterns align with classical PSCI deficits, such as neglect after right hemisphere strokes. However, other profiles weren’t linked to lesion location.
For example, one profile captured individuals with memory and executive dysfunction deficits which were more closely related to age-related cognitive decline than stroke. Other profiles captured people with no cognitive impairment and/or less classical PSCI deficits like neglect after left hemisphere lesions.
Lesion location alone isn’t enough to explain PSCI
Our analyses revealed that stroke lesion location isn’t enough to explain why individuals have different PSCI impairments. Lesion location (and the associated disconnection pattern) was related to PSCI profile for some, but not all types of PSCI impairment.
Additionally, the relationship between lesion location and PSCI profile weakened as the time between stroke and testing increased. As time between stroke onset and PSCI testing increased, overall measures of brain health (eg, atrophy severity) and education level were stronger predictors of PSCI profiles.
This indicates that brain health and education are strong predictors of PSCI Profiles. In our study, people with poor brain health and low education levels were more likely to have severe cognitive problems after stroke, even if their strokes weren’t more severe.
Our results suggest that “cognitive reserve” — the brain’s resilience to resist or delay declining cognitive function — is closely linked to cognitive problems in stroke. Many lifestyle factors help improve cognitive reserve, such as a healthy diet, regular exercise, good sleep, low stress levels, and strong social connections. Our finding is important because it indicates that improving cognitive reserve may lessen the cognitive impact of stroke.
Overall, our research represents a fundamental change in how cognitive problems are understood. Individual PSCI deficits are often researched and treated in isolation, and this research presents a novel approach for considering multiple different types simultaneously.
Big data and collaborative work is the future of PSCI research
Our research lays theoretical groundwork which can be built upon to improve PSCI support and care. It is likely that the PSCI profiles identified in this study can be applied to help predict long-term cognitive recovery outcomes and therefore guide targeted cognitive interventions.
Clear and compassionate communication about cognitive problems is essential for stroke survivors. The results of this study could be translated to create clinical tools supporting more effective communication and education about PSCI.
At a broader level, this research illustrates the importance of large-scale collaborative PSCI research. Our research would not have been possible in any single stroke cohort or research group alone as very large numbers and sample diversity were key factors enabling our detailed analyses.
Additionally, this study was conducted using entirely cognitive screening and imaging data collected as a component of routine clinical care. This type of data is widely available and often represents a key untapped research resource. It is therefore critically important for researchers and clinicians to explore avenues of large-scale collaboration and data sharing, to facilitate high-quality research into critical PSCI knowledge gaps.
PSCI has recently been identified as a key research priority, and collaborative, interdisciplinary, and large-scale research efforts are needed to meet this need and generate meaningful improvements in clinical PSCI care.
This research was conducted in collaboration with researchers at KU Leuven, the University of Oxford, the University of Queensland, NHS USL South-East Tuscany, and the Tuscany Rehabilitation Clinic.
Dr Margaret Moore is a Queensland Brain Institute researcher at The University of Queensland. She is an expert in stroke research, cognitive neuroscience and neuropsychology
The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated.
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