Episodic memory functioning in very old age : individual differences and utilization of cognitive support

Abstract

The general aim of the present doctoral thesis was to examine potential age-related differences in episodic memory performance and utilization of cognitive support in very old age. An additional objective was to investigate the influence of individual difference variables within demographic (e.g. education, gender), psychometric (e.g. general cognitive status; MMSE, fluid intelligence), lifestyle (e.g. social activity), and biological (e.g. serum vitamin B 12) domains on episodic memory functioning in late life. A population-based sample of normal adults between 75 and 96 years served as subjects. Across all five studies, participants were carefully screened for health, using a variety of exclusion criteria (e.g., depression, dementia, sensory loss).

In Study I, II, and III the aims were addressed employing several episodic memory tasks, including verbal and non-verbal materials, and examining utilization of cognitive support in the form of task-relevant prior knowledge, extended study time, copy cues at retrieval (recognition), organizability of the to-be-remembered materials as well as category cuing at retrieval. In these studies, the age-related deterioration of episodic memory performance was found to be slight, albeit reliable. Furthermore, the ability to utilize cognitive support appeared to remain unaffected by advancing age. Several individual difference variables including age, MMSE score, fluid intelligence, and level of formal education, were generally and positively related to memory performance. Study IV examined the impact of demographic and lifestyle factors on episodic memory and performance benefits due to the provision of cognitive support.

Results indicated that age was negatively related to performance, whereas education and participation in social activities exerted a positive influence. Exercise was also positively related to performance, but only in the least supported tasks. With regard to performance benefits due to cognitive support, education was positively related to benefits from more study time and item organizability, age was negatively related to the effect of item organizability, and social activity was positively associated with the ability to benefit from retrieval cues.

Study V explored the impact of low serum vitamin B12 and folic acid on episodic memory performance and utilization of cognitive support. It was found that participants with low levels of serum folic acid performed significantly worse than controls in both free recall and recognition of verbal materials, and that this deterioration was most pronounced in participants with low levels of both folic acid and vitamin B 12. However, vitamin status did not affect utilization of more study time or copy cues(recognition).

Overall, the five studies indicated that the well-known age-related deficit in episodic memory performance continues into very old age, although the ability to utilize the studied forms of cognitive support is less affected by advancing age. In addition to age, several individual-difference factors contributed to the amount of explained variance in both episodic memory performance and utilization of cognitive support, such that advantaged older persons (e.g. in terms of education and social activity) remembered more and benefited more from cognitive support. The results also indicate the relevance of including serum vitamin status as a health screening factor in research concerning age-related differences in episodic memory performance.