An evaluation of methods for measuring cognitive change in older adults
Date
2018-11-16
Authors
Frerichs, Robert John
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Abstract
Serial neuropsychological assessment of older adults requires well-researched statistical methods to guide clinicians in determining the significance of test score changes at the individual level. This study examined the standard deviation (SD) method, various reliable change indices (RCIs), and three standardized regression-based (SRB) methods in older adults who participated in one or more waves of the Canadian Study of Health and Aging (CSHA). Changes in test scores were examined in cognitively healthy older adults over a short test-retest interval of a few months and a longer interval spanning approximately 5 years. Test score changes were also compared to clinically significant indices including change in diagnostic status, subjective report of loss, informants' ratings of loss, and clinicians' rating of loss. The findings indicated that practice effects were not a prominent feature of older adults' performance. Mean decline was shown on neuropsychological tests of memory and psychomotor speed over a test-retest interval of approximately 5 years. At the individual level, normal variability in the test performance of cognitively healthy adults could be accurately classified using several methods over a short interval but only select methods over the longer interval. Two RCIs and three SRB methods were relatively accurate in classifying change among persons who remained cognitively intact and in those who had progressed to a dementia by follow-up 5 years later. A combination of memory measures and these change score methods resulted in diagnostic classification accuracy of approximately 89% in this sample. Diagnostic accuracy was also significantly associated with the sum of reliable test score changes using different change score methods. Reliable deterioration was moderately associated with clinicians' and informants' ratings of cognitive loss and weakly associated with subjective ratings of memory loss. These findings have implications for clinicians who seek to determine the meaning of neuropsychological test-retest score changes.
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Keywords
Cognition, Age factors, Memory