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Scientific research is not always accessible to the public, and popular media articles on research often sensationalize findings and fail to explain limitations. One of the aims of the Neurocognitive Disorders Lab is to make research clear, understandable, and accessible to the community. As part of this initiative, we post short critical summaries of recent research studies related to neurocognitive disorders. Check back regularly for summaries of new research:

Traumatic brain injury with loss of consciousness can lead to an earlier onset of alzheimer's disease

Summary by Morgan Schaeffer

     A recent study by Schaffert and colleagues (2018) explored whether traumatic brain injury (TBI; sometimes referred to as ‘concussion’) is associated with an earlier onset of dementia. To do this, the researchers examined the TBI history of 2153 participants from across the United States and examined their brains at autopsy. The researchers found that people who had sustained a TBI before being diagnosed with dementia had experienced dementia symptoms roughly three years earlier than those who had not sustained a TBI. These results suggest that TBI history may be a risk factor for developing dementia early.


     This study did have some limitations. First, there was no information regarding when the injury took place – it may have been during childhood or adulthood. There was also no information regarding the severity of the brain injuries or the presence of multiple injuries. This information would be valuable for determining who is most at risk for developing early onset dementia after sustaining a brain injury.

More information about this article can be found here.

depression and risk of alzheimer dementia: a longitudinal analysis to determine predictors of increased risk among older adults with depression

Summary by Baeleigh Ellement

     A study conducted by Gallagher, Kiss, Lanctot, and Herrmann (2018) explored the characteristics which place individuals with mild cognitive impairment (MCI) at a higher risk of developing Alzheimer’s Disease (AD). In this study, researchers looked at 1965 participants with MCI and depression and followed them over a period of 27 months. Over the follow-up period, 39.7% of the participants developed AD; of those who progressed to AD, 84.5% had active depression in the last two years. The researchers believe this is an essential characteristic for clinicians to keep in mind when considering the risk of developing AD. Active depression in the last two years may reflect a more aggressive development of AD and AD pathology. For such reasons, clinicians should pay particular attention to those who present with active depression in the last two years. 

     Other factors that the researchers determined to play a significant role in the development of AD included: age, the score on a neuropsychological test of cognitive function (the Mini Mental Status Examination), a specific subtype of MCI (the amnestic subtype) and finally, an allele highly implicated in the development of AD (the APOE e4 allele). The researchers noted that each of these factors should be considered as a markers of high risk of AD progression. 

     This study is not without limitations. This study was conducted using a sample of participants which was highly convenient and easily accessible. The participants were those who attended specialist memory services and thus do not represent the general population. As well, the follow-up period of 27 months is relatively short and more participants may have progressed to AD beyond that period. 

More information about this article can be found here.

cerebrospinal fluid cortisol and clinical disease progression in mci and dementia of alzheimer's type

Summary by Vivian Huang

     A study by Popp and colleagues (2015) examined whether dysfunction of the stress system among patients with mild cognitive impairment (MCI; i.e., a transitional stage between healthy cognition and dementia) and whether cortisol levels found in blood and cerebral spinal fluid (CSF) are associated with cognitive decline over time among patients with MCI and Alzheimer’s disease (AD). A total of 147 individuals with MCI, 105 AD patients, and 35 individuals with normal cognition participated in the study. Participants completed tasks that assessed different aspects of their cognitive function. Participants also provided blood and CSF samples to assess their stress system function via cortisol, a stress hormone. It was found that participants with MCI due to AD and participants with AD have higher CSF cortisol levels compared to participants with normal cognition and participants with MCI due to other causes. Further, higher CSF cortisol levels at the first visit were associated with significant cognitive decline approximately 2 years later for participants with MCI due to AD and participants with MCI due to other causes. There was no significant association between cortisol levels at first visit and later cognitive decline among participants with AD. 


     It is important to note that CSF cortisol extraction was done via spinal puncture. Such extraction method is highly invasive and stressful. Therefore, the cortisol extraction method could serve as a limitation of this study. The present findings suggest that dysfunction of the stress system could serve as a contributing factor for further cognitive decline over time at the prodromal stages of AD. 

More information about this article can be found here.

physical activity improves verbal and spatial memory in older adults with probable mild cognitive impairment: a 6-month randomized controlled trial

Summary by Azra Sorathia

     A study by Nagamatsu and colleagues (2013) explored how physical activity can improve verbal and spatial memory in older adults with probable mild cognitive impairment. The participants were 86 females, aged between 70-80 years old who all had probable mild cognitive impairment. Participants were randomly assigned to 2 exercise groups consisting of aerobic training and resistance training. Examples of aerobic training are walking, jogging, and swimming. Examples of resistance training are weight lifting, squats, and lunges.

     Results of the study show that participants who engaged in twice-weekly aerobic training for 6 months remembered significantly more items on the verbal memory test. Both types of exercises improved reaction times during the spatial memory test compared to the control group. These results suggest that pursuing a healthy lifestyle can indeed help with cognitive functioning when aging.

     This study does have limitations, namely the fact that men were excluded and only individuals between the ages of 70-80 were included. Nagamatsu and colleagues only saw results after 6 months and not 3 months, therefore the dose-response relationship of the exercises need to be clarified so that future recommendations for the most successful programs can be given to the public.

More information about this article can be found here.

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