Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made.  (Formerly, these situations were captured under a "C Recommendation".)  This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade.  For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.

Preventive Health Care, 2001 update: Screening for cognitive impairment and dementia in the elderly

Structured Abstract

Prepared by Christopher J.S. Patterson, MD, FRCPC, Professor, Division of Geriatric Medicine, McMaster University, Hamilton, Ontario and David A. Gass, MD, Department of Family Medicine, Dalhousie University, Halifax, Nova Scotia, with the Canadian Task Force on Preventive Health Care.

These recommendations were finalized by the Task Force in 1999.

Objective

To make recommendations about screening for cognitive impairment and dementia in the elderly by primary care practitioners. A previous review by the Canadian Task Force on Preventive Health Care in 1994 had concluded that there was insufficient evidence to recommend for or against screening with short mental status instruments but that physicians should remain alert for any symptoms suggestive of cognitive impairment and conduct an appropriate assessment.

Burden of Suffering

The overall incidence of dementia among Canadians over age 65 years is about 19 per 1,000 persons per year. While the total prevalence of dementia rises sharply above age 75, for those living in the community, and who are most likely to be the target for screening, the prevalence remains quite low. The community prevalence of dementia in Canada increases from 1.6% of those age 65-74 years to 17.8% of elderly aged 85 or older. Risks to the individual (e.g. accidental injury) and stress to the caregivers increase significantly as the disease progresses. The financial burden including medications, care giving and institutional care, increases with the severity. Individuals with dementia have reduced survival.

It is difficult to estimate incidence of cognitive impairment as there are different definitions and individuals are often not aware of their impairment. The prevalence of cognitive impairment has been estimated between 11% (cognitive impairment- no dementia: ages 65-74) and 98% (memory impairment on at least one objective test). While dementia is progressive, the natural history of cognitive impairment is less clear. Estimates of the rate of progression from cognitive impairment to dementia range widely from less than 1% to 16% per annum. It is possible to predict which individuals have a higher risk of progression to dementia through various neuropsychological tests. Individuals with specific alleles of the ApoE gene are more likely to progress to Alzheimer’s type dementia. There is an established relationship between the risk of dementia and lower levels of education.

In Canada, Alzheimer’s disease accounts for 60 or 70% of dementia cases. The second most common type is mixed dementia, the presence of cerebrovascular disease superimposed on Alzheimer’s pathology. Other causes include: degenerative neurological conditions such as Parkinson’s disease, progressive supranuclear palsy, Huntington’s disease and the late results of exposure to head injuries or neurotoxins such as alcohol and heavy metals.

Options

Outcomes

Evidence

Recommendations were graded as:

A	Good evidence to support the recommendation that the condition be specifically considered in a PHE.
B	Fair evidence to support the recommendation that the condition be specifically considered in a PHE.
C	Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.
D	Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.
E	Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

Quality of evidence was rated according to 5 levels:

I	Evidence from at least 1 properly randomized controlled trial (RCT).
II-1	Evidence from well-designed controlled trials without randomization.
II-2	Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.
II-3	Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.
III	Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.

Values

The 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions.  Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the authors were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 3 meetings from Jan. 1998 to Oct. 1998. Consensus was reached on final recommendations.

Benefits, Harms, and Costs

The Mini Mental State examination (MMSE) has average sensitivity of 83% and average specificity of 82% and is brief and easily applied in a primary care setting. However the rate of false positive findings must be considered. Screening populations with mental status questionnaires can identify groups at risk for progression to dementia. Follow-up investigation is necessary to distinguish those who have mild impairment due to physical illness or medication, depression, mental retardation, early dementia, or who are cognitively normal.

There are effective strategies for managing individuals with established dementia with both supportive and drug therapies. Some drug therapies have produced modest clinical improvements. However the value of these interventions in individuals with cognitive impairment who are not demented, or in those with dementia discovered by screening is not yet known.

Potential benefits of early detection include providing the chance for individuals and their caregivers to plan ahead, to find social support, housing, power of attorney, etc., but have not been systematically studied. The positive effects must be weighed against potential negative effects of mislabeling a significant number of older individuals with an unpleasant diagnosis, and possibly subjecting them to further unnecessary investigations.

Recommendations

• There is insufficient evidence to recommend for, or against, screening for cognitive impairment in the absence of dementia [C, II-2].
  
• Memory complaints should be evaluated and the individual followed to assess progression [B, II-2].
  
• When caregivers or informants describe cognitive decline in an individual, these observations should be taken very seriously: cognitive assessment and careful follow-up are indicated [A, II-2].

Validation

This paper was peer reviewed as part of the journal publication process. The Canadian Consensus Conference on Dementia also reviewed this evidence and concurred with the recommendations.

Sponsors

Selected References

Patterson CJS, Gass DA. Screening for cognitive impairment and dementia in the elderly. Can J Neurol Sci 2001; 28(Suppl 1):S42-51.