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

Abstract

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.

Figure 1

Total NINL scores for all sessions. In dropouts and finishers, there was a genotype × session interaction. * indicates that a score was significantly lower in the baseline session at P < 0.05. n =114

Figure 2

Change in total NINL scores of non-ε4 and ε4 dropouts and finishers (non-ε4 n = 72; ε4 n = 16) between the baseline and the follow-up sessions. In finishers, there was a genotype × session interaction. Decreased scores resulted in a negative change value (−). n = 114

Figure 3

Incorrect ‘no change’ (NC) responses. In the baseline session, ε4 dropouts had significantly more incorrect ‘NC’ responses than non-ε4 dropouts, non-ε4 and ε4 finishers. * indicates significance in the baseline session at P < 0.05 n = 114

Figure 4

A. Inset shows average ‘novel location’ (NL) sub-scores over all three sessions. B. Total novel location (NL) sub-scores in the 3 individual sessions. In dropouts and finishers, there was a genotype × session interaction. * indicates a significantly lower collapsed score over time at P < 0.05. n = 114

Figure 5

Salivary cortisol levels in dropouts and finishers. In dropouts and finishers, there was a significant decrease in hormone levels over the sessions P < 0.05. n = 107

Figure 6

Salivary testosterone levels in dropouts and finishers. In dropouts and finishers, there was a significant decrease in hormone levels over the sessions P < 0.05. n = 105