Repeated Cognitive Testing Can Obscure Early Signs of Dementia

A study published in Alzheimer's & Dementia: Diagnosis, Assessment, & Disease Monitoring found repeated testing of middle-age men generates a "practice effect" which obscured true cognitive decline and delayed detection of mild cognitive impairment, reports UC San Diego Health . Researchers re-tested 995 men in a six-year follow-up of an earlier study, while a second cohort of 170 age-matched males were tested for the first time. The team noticed significant practice effects in most cognitive domains, and diagnoses of MCI rose from 4.5 percent to 9 percent after correcting for practice effects. "In other words, some men would have declined to levels indicating impairment on follow-up testing had they not been exposed to the tests before," says UCSD Professor William S. Kremen. The researchers note the clinical significance is that Alzheimer's treatment is shifting increasingly toward prevention strategies that are dependent on early identification. They say their findings strongly hint at the value of correcting for practice effects in longitudinal studies of older adults, such as using similar replacement persons taking the test for the first time.