Benefits of Dementia Screening Still Unclear

Pauline Anderson

October 24, 2013

Dementia screening instruments, such as the Mini-Mental State Examination (MMSE), can adequately pick up cognitive impairment in the primary care setting, but many of these tools have not been extensively studied, and there's no empirical evidence that using them improves decision-making or important outcomes, according to a new literature review.

The review authors also suggest that despite decades of research, it's still unclear whether cognitive or exercise interventions have a clinically significant effect.

The review was published online October 21 in the Annals of Internal Medicine.

No Basis for Routine Screening

Primary care clinicians may fail to recognize cognitive impairment using routine history and physical examination, according to the study authors. Most patients aren't diagnosed until at least the moderate stage of the disease, they note.

In 2003, the US Preventive Services Task Force (USPSTF) concluded that there was insufficient evidence to recommend for or against routine screening for dementia in older adults. The current review was conducted in an effort to update these recommendations.

The review included 5 key questions:

  1. Does screening for cognitive impairment in community-dwelling older adults in primary care settings improve decision making or patient, family, caregiver or societal outcomes?

  2. What is the test performance of screening instruments to detect cognitive impairment in these elderly patients?

  3. What are the harms of screening?

  4. Do interventions for mild cognitive impairment (MCI) or mild to moderate dementia improve decision-making or outcomes?

  5. What are the harms of interventions for cognitive impairment?

An extensive review of the literature turned up no studies to answer the first question and only 1 study that addressed the third question. The review therefore concentrated on questions 2 (with 55 fair- to good-quality studies), 4 (131 studies), and 5 (66 studies).

Although the new review included twice the number of studies than existing reviews, its findings were generally consistent with previous findings.

Only 12 brief instruments have been assessed more than once in well-designed studies evaluating their ability to detect dementia in primary care–relevant populations. Only 4 studies were of good quality, with the rest having fair quality and various risks of bias.

In this analysis, the MMSE was the best-studied instrument, with pooled estimates across 14 studies resulting in a sensitivity of 88.3% and a specificity of 86.2% for the most commonly reported cut points. But the MMSE has the longest administration time and is not available for public use without cost, said the authors.

The Clock Drawing Test, Mini-Cog, Memory Impairment Screen, Abbreviated Mental Test, Short Portable Mental Status Questionnaire, Free and Cued Selective Reminding Test, 7-Minute Screen, and Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) are available for public use in primary care settings but have been studied only in English.

Most of these instruments can have an acceptable test performance, but not much evidence supported their use, with reproducibility in primary care populations limited and optimum cut-points unknown, according to the authors.

Only 6 instruments were used in more than 1 study assessing diagnostic accuracy to detect MCI in primary care populations. Overall, the sensitivity for detecting MCI for each of these instruments, except for the IQCODE, was lower than that for detecting dementia.

Screening Harmful?

The reviewers identified 1 systematic review and 118 trials that addressed the benefits of the treatment or management of mild to moderate dementia, MCI, or both. Most trials (90%) were of fair quality. Medication trials were exclusively or partially industry funded.

The review included a well-conducted systematic review of US Food and Drug Administration–approved medications for the treatment of Alzheimer's disease that included 39 randomized controlled trials of acetylcholinesterase inhibitors (AchEIs), as well as 9 additional randomized controlled trials.

Overall, on the basis of these fair- to good-quality trials, AchEIs can improve cognitive function and global functioning in the short term, but the pooled magnitude of these changes is small, with a change of about 1 to 3 points on the Alzheimer`s Disease Assessment Scale-Cognitive Subscale (ADAS-cog).

"The average effect of these changes may not be clinically meaningful as defined using commonly accepted values," the authors write.

It's still unclear whether AchEIs can improve physical functioning "given the inconsistent and sparsely reported findings," they add.

On the basis of 10 fair- to good-quality trials of memantine, a drug approved for moderate to severe AD that has also been evaluated in patients with mild to moderate dementia or MCI, this agent had a benefit similar to that seen with AchEIs on global cognitive functioning in patients with moderate dementia.

These small average effects of change in cognitive function with AchEIs and memantine must be balanced by common adverse effects associated with them, the authors note.

None of the trials of other medications or dietary supplements, including low-dose aspirin, nonsteroidal anti-inflammatory drugs, and vitamins, found a benefit on cognitive or physical function in people with mild to moderate dementia or MCI.

The review found no studies to substantiate or refute concerns about harms of screening. However, the authors said that the harms of screening are poorly studied.

"Some have argued that these harms are minimal, whereas others have argued that the harms of screening and mislabeling persons with dementia are real given the variation in practice of diagnostic confirmation of disease. If broader adoption of screening for cognitive impairment is implemented, it would be wise to better understand these tradeoffs."

Caregiver Burden

Overall, in trials of interventions targeting caregivers, there was generally a consistent finding of small benefit on caregiver burden and caregiver depression outcomes.

Pooled analyses of 24 trials showed a small but statistically significant effect (standardized mean difference, –0.23 [95% confidence interval (CI)], –0.35 to –0.12l) on caregiver burden. And pooled analyses of 30 trials showed a small but statistically significant effect (standardized mean difference of 0.21 [95% CI, –0.30 to –0.13]) on caregiver depression.

"The clinical meaning of these changes in caregiver burden and depression are, on average, probably small at best," the authors write.

As well, the authors pointed out that many of the studies of complex interventions for caregivers were conducted outside the United States and may not be freely available.

There was limited reporting of findings for outcomes such as global stress or distress, anxiety, and health-related quality of life for caregivers.

Although evidence is limited and findings inconsistent, cognitive stimulation with or without cognitive training seemed to improve global cognitive function at 6 to 12 months for patients with MCI or dementia. However, the authors add, "the certainty and magnitude of effect of cognitive stimulation is still unclear."

Exercise interventions also have limited evidence to support their use in patients with MCI or mild or moderate dementia. However, 3 of the better-conducted trials did suggest a benefit of exercise in global cognitive function or physical functioning and health-related quality of life.

The review did not address several important aspects of screening test performance, including the psychometric properties of testing other than sensitivity and specificity.

According to expert consensus guidelines, early detection of cognitive decline may lead to optimal medical management and ultimately lead to improved patient outcomes and reduced costs, but there is little or no empirical evidence to support this, the authors concluded.

"How and whether clinician decision-making and patient and family decision-making are affected by earlier identification of cognitive impairment or earlier management of patients with dementia and their caregivers are important aspects to understand in order to better manage this rapidly growing health care problem," they write.

Research comparing which criteria — for example, age, comorbid conditions, or functional status — should lead primary care clinicians to perform cognitive assessment is much needed, the authors add. Additional evaluation of brief instruments in more representative populations is also needed.

Right Decision

Commenting on the review for Medscape Medical News was Malaz Boustani, MD, chief operating officer, Indiana University Center for Innovation and Implementation Science and chief innovation and implementation officer, Indiana University Health, Indianapolis.

Dr. Boustani's research team, with support from the National Institute on Aging, is conducting the first randomized controlled trial to evaluate the benefit and harm of dementia screening in primary care. The trial has now enrolled more than 500 patients (of an eventual target of 4000) and final results are expected in 2017.

According to Dr. Boustani, the USPSTF decision not to recommend routine screening for dementia in primary care was the right one.

"The required data to make such an important and vital decision is not there yet," he said.

J. Riley McCarten, MD, associate professor, Department of Neurology, University of Minnesota Medical School, medical director, Geriatric Research, Education and Clinical Center (GRECC), and medical director, The Memory Clinic, University of Minnesota Medical Center, Minneapolis, believes that the time for screening has arrived.

"We have the tools to identify dementia and to intervene" in what is a costly and rapidly growing major health care problem, said Dr. McCarten. "To successfully address this tragedy, we must first make diagnosing it a priority."

Dr. McCarten took issue with the study authors' conclusion that although screening can identify people with dementia, no empirical evidence exists to determine whether interventions affect decision-making. "Pretending that knowing whether someone has dementia has no effect on decision-making is illogical—and dangerous," he said.

It's impossible to "uncouple" identifying dementia—in this case, through screening—from decision-making about dementia, said Dr. McCarten. "Once dementia is identified, decisions are made based on that knowledge."

Screening identifies patients for whom an intervention is needed, and the intervention necessarily involves decision-making specific to each patient, provider, and family, added Dr. McCarten. "We end up comparing a variety of interventions based on decisions made by and for persons with known dementia."

Dr. Lin's has received support from the Agency for Healthcare Research and Quality. Dr. Boustani and Dr. McCarten have disclosed no relevant financial relationships.

Ann Intern Med. Published online October 21, 2013. Full text

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