Duration of the Assessment
Some formal neuropsychological assessment batteries can take 6 to 12 hours or more to complete. Duration of the assessment is generally correlated with level of detail, but an assessment of episodic memory can take an hour itself while an abbreviated but wide-ranging assessment of cognition often used in clinical trials can take as little as 20 minutes (Keefe et al., 2004). It depends on the measures selected for the assessment.
Longer assessments pose challenges from two directions. If an intervention trial has multiple assessments other than cognition, then a cognitive assessment with a long duration may increase the length of a study visit to the point that it is not practical. The other point is that some populations are challenged by long assessments. For instance, it is not a surprise to see that children who have difficulty sustaining their attention in school have similar problems tolerating long psychological assessments, which can lead to misleading results. Older adults can also become fatigued. In general, however, even patient populations such as those with schizophrenia can provide valid data with cognitive batteries requiring approximately 75 minutes of assessment time (Keefe et al., 2011; Neuchterlein et al., 2008).
The take-home principles from this discussion are that the shortest possible assessment that evaluates important aspects of cognition is the best strategy; however, attention must be paid to important psychometric characteristics of the data collected, such as the psychometric qualities of the assessment (see Chapter 14) and most importantly whether enough information is being collected to allow meaningful conclusions about the impact of an intervention. There are no generic answers for how long and how broad the assessment should be. It depends on the nature of the intervention strategies, targeted outcomes, and target populations.