Association between long‐term Environmental Enrichment and Memory‐Related Functional Brain Activity in the DELCODE cohort

Abstract Background Environmental factors account for a considerable percentage of dementia cases. Studies in animal models have shown that environmental enrichment (EE; i.e., stimuli‐rich housing conditions) has positive effects on brain structure, including the memory system. In humans, EE as measured by the engagement in a variety of leisure activities has been associated with better fornix structure and memory (Klimecki et al., 2023). We assessed whether long‐term EE (in terms of engagement in diverse leisure activities) is related to functional brain activity in the memory system of older adults. Methods We operationalized individual EE in 372 older participants aged between 60 and 87 years of the DZNE Longitudinal Study on Cognitive Impairment and Dementia (DELCODE) study. We used subscales of the Lifetime of Experiences Questionnaire (LEQ; Valenzuela & Sachdev, 2007) that capture the frequency of engagement in diverse leisure activities in young adulthood and middle life (13‐30 and 30‐65 years). Memory‐related brain activity was assessed using individual FADE‐SAME scores in a functional magnetic resonance imaging (fMRI) paradigm on visual memory encoding and recognition. The scores capture the similarity of older adults’ brain activity patterns with typical activations of younger adults’ (Soch et al., 2021). We performed multiple regression analyses between long‐term EE as independent variable and FADE‐SAME scores related to novelty processing and subsequent memory as dependent variables. Result Long‐term EE was significantly associated with novelty‐based SAME scores. More specifically, older participants with higher EE in early and middle life showed a higher similarity of functional brain activity patterns during novelty processing with the patterns seen in younger adults (see Figure 1). Exploratory subgroup analysis showed that this association was predominantly found in participants with Subjective Cognitive Decline (SCD, n = 199). No other significant findings were obtained. Conclusion Engagement in a variety of leisure activities during early and middle life is related to more “youth‐like” memory‐related brain activity patterns in older adults, including older individuals at increased risk of AD. Higher EE during early life might contribute to preservation or promotion of memory functions in later life.