Citing an ongoing lack of data about the benefits and harms of screening, the U.S. Preventive Services Task Force has left unchanged the recommendations of its 2003 guidelines on cognitive impairment screening in older adults, according to an update published March 24.
"The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for cognitive impairment," Dr. Virginia A. Moyer said in a report on behalf of the USPSTF.
"Evidence on the effect of screening and early detection of mild to moderate dementia on decision making, planning, or other important patient outcomes is a critical gap in the evidence," she added. Other research needs include further study of the harms of screening, new interventions that address the changing needs of patients and families, and interventions that affect the long-term clinical direction of mild to moderate dementia.
In its review, the USPSTF evaluated 55 studies on instruments that screen for cognitive impairment, of which 46 provided evidence on the sensitivity of dementia screening and 27 provided evidence on mild cognitive impairment. Screening tests included a variety of tasks to assess at least one cognitive function, such as memory, attention, language, and visuospatial/executive functioning. The USPSTF looked at studies that used the Mini-Mental State Examination (MMSE), Clock Drawing Test, verbal fluency tests, Informant Questionnaire on Cognitive Decline in the Elderly, Memory Impairment Screen, Mini-Cog Test, Abbreviated Mental Test, and Short Portable Mental Status Questionnaire.
The MMSE was the most evaluated screening tool, with 25 published studies. Mean age of participants ranged from 69 to 95 years, and the mean prevalence of dementia ranged from 1.2% to 38%. The pooled sensitivity from 14 studies for the most commonly reported cut points was 88.3% (95% confidence interval, 81.3%-92.9%), and specificity was 86.2% (CI, 81.8%-89.7%).
Other screening tools that were evaluated "were studied in far fewer studies (four to seven studies each), had limited reproducibility in primary care relevant populations, and had unknown optimum cut points," Dr. Moyer wrote.
In addition, no trials studied the "direct effect of screening" by comparing screened and unscreened patients and reporting important clinical and decision-making outcomes, the report’s authors said. And no studies reported on direct or indirect harms from false-positive or false-negative screening results, psychological harms, unnecessary diagnostic testing, or labeling.
Dementia affects about 2.4 to 5.5 million Americans. Types of dementia in older adults include Alzheimer’s disease, vascular dementia, frontotemporal dementia, dementia with Lewy bodies, Parkinson’s disease with dementia, and mixed-cause dementia. The USPSTF distinguishes between dementia and mild cognitive impairment, which is less severe and does not considerably interfere with day-to-day activities.
The prevalence of dementia is estimated to be 5% in adults aged 71-79 years of age, 24% in those aged 80-89 years, and 37% in those aged 90 years and older. The prevalence of mild cognitive impairment is more uncertain, and estimates range from 3% to 42% in adults aged 65 years and older.
Although this report differs from the 2003 recommendation because it considers screening and treatment for mild cognitive impairment in addition to dementia, and it includes additional information about the test performance of screening instruments, "the overall evidence is insufficient to make a recommendation on screening," Dr. Moyer said.
Disclosure forms from USPSTF members can be viewed here.