Dementia in Canada

We are going to reproduce a paper written by the Population Health Expert Panel for the Canadian government. We hope that you find these informative and helpful.

Larry W. Chambers, Christina Bancej and Ian McDowell, Editors

Variability in Cognitive Aging

There is a wide spectrum of types of cognitive impairment and dementia, and these conditions have varied causes and consequences.
In 2015, 80 years is the average age of onset of dementia (Grignon et al 2015).
According to the recent review entitled “Cognitive Aging” (Institute of Medicine 2015), cognitive aging differs in the populations of 60 year olds, 70 year olds, 80 year olds and those 90 and over.
And the increased likelihood of co-existing cardiovascular disease, diabetes and dementia with advancing aging exacerbate cognitive declines (Bunn et al 2014).
Further, studies of populations show that older people perform less well, and cognitive health differs according to educational background, health status, literacy, culture, ethnicity, skills, abilities, and life experiences.
Also, a person’s cognitive trajectory over time is dynamic with ups and downs because of environmental stressors, medications or illnesses.
Dementia is one of the main causes of disability later in life, ahead of cancer, cardiovascular disease and stroke.
On a positive note, the Institute of Medicine review points to the concept of neural plasticity and findings that older adults learn new skills and improve cognitive performance, and that they have a wealth of knowledge, skills and experience younger people may not have.

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Measurement of Cognitive Impairment and Dementia

Dementia refers to progressive impairments in memory and other cognitive functions.
A diagnosis of dementia is based on a pattern of signs & symptoms such as the ten warning signs of dementia:

  1. Memory loss that affects day-to-day abilities,
  2. Difficulty performing familiar tasks,
  3. Problems with language such as forgetting or using wrong words,
  4. Disorientation in time and space,
  5. Impaired judgment,
  6. Frequent problems with complicated tasks,
  7. Misplacing things,
  8. Sudden changes in mood and behavior,
  9. Changes in personality, and
  10. Loss of interest in doing things (Alzheimer Society of Canada 2015).

Dementia lies at the severe end of a spectrum of cognitive disorders and the level of disability and need for care rises across the spectrum.
It is difficult to set a precise threshold between cognitive impairment and dementia.

The US Preventive Services Task Force (Lin at al 2013) identified the following cognitive impairment screening tests as accurate as their psychometric properties are reported to be greater than 80 to 90 percent sensitivity and specificity:

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  • Mini-Mental State Exam
  • Clock drawing test
  • Mini-cog test
  • Memory impairment screen
  • Abbreviated mental test
  • Short Portable Mental Status Questionnaire
  • Free and cued selective reminding test
  • 7-minute screen
  • Telephone Interview for Cognitive Status
  • Information Questionnaire on Cognitive Decline in the Elderly

International population surveys of prevalence of mild cognitive impairment estimates vary from 5% to 37% (Sachdev et al 2015).
Sometimes “mild cognitive impairment”, typically identified using one or more of these screening tests, is counted as “dementia” in population prevalence estimates.
However, only about 60% of people with mild cognitive impairment progress to dementia and experience disability (Savva et al, 2009).
Changing the threshold for ‘dementia’ to Include mild cognitive impairment may create new patients (over diagnosis) and, in clinical settings, result in overtreatment (Figure 1) (Welch et al 2011, Lin et al 2013, Institute of Medicine 2015).
The Gerontology Society of America Workgroup on Cognitive Impairment Detection and Earlier Diagnosis (2015) concluded there is lack of evidence that specific medical conditions or functional limitations are inevitably linked to development of any type of dementia.
And, this Workgroup went further, choosing not to endorse any specific risk factors for dementia that would automatically trigger the need for cognitive assessment (The Gerontology Society of America Workgroup on Cognitive Impairment Detection and Earlier Diagnosis 2015).3.0 Measurement of Cognitive Impairment and Dementia

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