Effects of epsilon4 on object recognition in the non-demented elderly.

Previously we reported that apolipoprotein E (ApoE) epsilon4 negatively affects performance in the novel-image-novel-location (NINL) object recognition test in healthy non-demented elderly human study participants. In this study, the participants were invited to return for testing sessions 6 and 18 months after the baseline session. Using a longitudinal study design, effects of epsilon4 on NINL test performance were assessed in study "dropouts", participants that did not return for the second and/or third session(s), and "finishers", participants that returned for all sessions. There were effects of epsilon4 on dropout rates and NINL total scores as well as sub-scores in both dropouts and finishers. NINL total score was a predictor of epsilon4 participant dropout. Compared to non-epsilon4 dropouts, epsilon4 dropouts had lower NINL scores. In contrast, epsilon4 finishers had higher NINL scores than non-epsilon4 finishers. Thus, the NINL test could be a valuable tool in detecting pre-clinical signs of age-related cognitive impairments, particularly those associated with epsilon4 risk.