Measuring cognitive change in older adults: reliable change indices for the SIDAM.
BACKGROUND
In clinical settings, neuropsychological tests and screening instruments are often used to measure cognitive change over time. However, the interpretation of changes in test scores is often difficult. For most instruments there is no information how much change occurs normally in cognitively healthy individuals.


OBJECTIVE
To examine what is a reliable change for a widely used screening instrument for cognitive impairment and dementia.


METHODS
A Sample of 119 cognitively normal elderly individuals aged 75 and over participated in the Leipzig Longitudinal Study of the Aged (LEILA 75+). All participants have been tested six times at 1.5 year intervals with the test part of the SIDAM over a mean period of 7.1 years. Reliable change indices (RCI) were computed for a common confidence interval (90%). It is demonstrated how to compute RCI for individual patients.


RESULTS
In repeated assessments with 1.5 year intervals, a change in SIDAM score of at least 4 to 7 points (dependent on which of the six assessments were compared) indicates a reliable change at the 90% confidence level. Smaller changes can be interpreted only with high uncertainty.


CONCLUSIONS
The interpretation of changes in test scores in older adults should account for potential practice effect, normal decline and regression to the mean.
Hensel
Anke
A
Dept. of Psychiatry, Research Department of Evaluation and Epidemiology, University of Leipzig, Johannisallee 20, 04317, Leipzig, Germany. Anke.Hensel@medizin.uni-leipzig.de
Angermeyer
Matthias C
MC
Zaudig
Michael
M
Riedel-Heller
Steffi G
SG
D000368:Aged; D000369:Aged, 80 and over; D003071:Cognition / Q000502:physiology*; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D009483:Neuropsychological Tests; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013997:Time Factors