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An international collaboration led by researchers from UNSW Sydney’s Centre for Healthy Brain Ageing (CHeBA) has offered new insights into what happens to cognitive function following a stroke and which risk factors lead to faster cognitive decline.
It is currently estimated that one in four people globally will have a stroke in their lifetime1, with more than 445,087 Australians currently living with the effects of stroke2.
Although post stroke loss of cognitive ability is common, the trajectory and full extent of brain changes after stroke remains unclear.
Lead author and Study Coordinator of the Stroke and Cognition Consortium (STROKOG), Jess Lo, said the researchers wanted to find out how the cognitive performance of stroke survivors changes over time.
“STROKOG is an international collaboration which brings together post-stroke cohort studies. By performing analyses on combined datasets, this collaboration sets out to better understand the determinants of cognitive decline and dementia after stroke, as well as improve the diagnosis and treatment of post-stroke cognitive disorders,” said Lo.
“In this study we wanted to learn whether brain function declines rapidly at a steady state soon after having a stroke.”
The researchers also set out to determine the risk factors for cognitive decline after stroke.
The analysis, published in Stroke, included 9 studies from STROKOG across 7 countries, including Australia, Asia, Europe and the United States. 1488 stroke patients with ischaemic stroke and a mean age of 66 years were included in the study. The patients were followed up for a median of 3 years.
We discovered that the cognitive function of stroke survivors improves for a short period soon after a stroke and then decreases – beginning from around one-year poststroke.
“The decline in stroke patients was small, but faster than that of individuals without stroke, and those with a second stroke during follow up had a much faster rate of cognitive decline.”
“We also found that the decline in older stroke patients, compared with younger stroke patients, happened more quickly,” said Lo.
According to Lo this research is significant because the results have implications for the design of clinical trials of therapies to prevent or slow poststroke cognitive decline, which should take into consideration the trajectory of initial improvement and subsequent decline in cognition after stroke. Our results could also help clinicians better understand and plan for the long-term needs of patients with stroke.
The limitations of the study include the relatively short follow-up period in some studies that limited our estimation of the course of cognitive function to 3 years and individuals with poorer baseline cognitive function dropping out of the study.
The initial period of improvement was likely to have been the result of a combination of genuine recovery as well as practice effects, which means that participants may achieve higher test scores in the follow up assessments since they completed the same tests at least once prior. While it is out of scope to address this initial period of improvement in this paper, it is the focus of our next research.
Co-Director of the Centre for Healthy Brain Ageing and co-author on the research, Professor Perminder Sachdev, said that the research justified further research to develop strategies to decrease cognitive decline following stroke.
“The traditional focus in stroke rehabilitation has been on physical recovery and speech therapy, and cognitive function has been relatively neglected. This work provides additional evidence that cognitive assessment of stroke patients is important and their cognitive complaints should not be ignored,” said Professor Sachdev.
1GBD 2016 Lifetime Risk of Stroke Collaborators, Feigin VL et al. Global, Regional, and Country-Specific Lifetime Risks of Stroke, 1990 and 2016. N Engl J Med. 2018; 379(25):2429-2437
2 Deloitte Access Economics. 2020. No postcode untouched, Stroke in Australia 2020