Practice effects in the prediction of long-term cognitive outcome in three patient samples: A novel prognostic index

Abstract

Practice effects, defined as improvements in cognitive test performance due to repeated exposure to the test materials, have traditionally been viewed as sources of error. However, they might provide useful information for predicting cognitive outcome. The current study used three separate patient samples (older adults with mild cognitive impairments, individuals who were HIV+, individuals with Huntington's disease) to examine the relationship between practice effects and cognitive functioning at a later point. Across all three samples, practice effects accounted for as much as 31-83% of the variance in the follow-up cognitive scores, after controlling for baseline cognitive functioning. If these findings can be replicated in other patients with neurodegenerative disorders, clinicians and researchers may be able to develop predictive models to identify the individuals who are most likely to demonstrate continued cognitive decline across time. The ability to utilize practice effects data would add a simple, convenient, and non-invasive marker for monitoring an individual patient's cognitive status. Additionally, this prognostic index could be used to offer interventions to patients who are in the earliest stages of progressive neurodegenerative disorders.

Short-term practice effects in amnestic mild cognitive impairment: implications for diagnosis and treatment

“…Conversely, individuals with amnestic MCI have been reported to demonstrate practice effects on cognitive and motor tests across brief retest periods (Yan and Dick, 2006;Duff et al, 2007). The equivocal findings in the literature could be attributed to several factors, including small sample sizes (Duff et al, 2007), limited assessment batteries (Cooper et al, 2004;Schrijnemaekers et al, 2006;Yan and Dick, 2006), or long retest periods (Galvin et al, 2005;Schrijnemaekers et al, 2006).…”

“…Using only one-week data, nearly half of our MCI participants improved so much that they were reclassified as "intact" after one week, whereas the other half retained their MCI status. We have previously suggested that these two subgroups might have differential courses and outcomes (Duff et al, 2007), but this needs further investigation.…”

“…The equivocal findings in the literature could be attributed to several factors, including small sample sizes (Duff et al, 2007), limited assessment batteries (Cooper et al, 2004;Schrijnemaekers et al, 2006;Yan and Dick, 2006), or long retest periods (Galvin et al, 2005;Schrijnemaekers et al, 2006). Given these discrepancies in the literature, the current study sought to compare practice effects in older adults with amnestic MCI with peers with intact cognition.…”

“…For example, it is necessary to know whether some degree of practice effects are expected in amnestic MCI participants before initiation of a drug. Second, practice effects could provide clinically useful information about progression of the illness (Duff et al, 2007). Third, it is likely that some tests are more susceptible to practice effects, whereas others are not, and a more comprehensive examination of practice effects across multiple cognitive domains could be fruitful.…”

Mood, Cognitive Function and Quality of Life Improvements in Middle Aged Women Following Supplementation with Polygonum minus Extract

“…However, the following administration did not show any improvement in the test performance. Although practice effect has been linked as a source of error, earlier study has suggested that it can be a beneficial tool to monitor cognitive status specifically among patients with neurodegenerative disorders at earlier stage (Duff et al 2007). …”