Factors Related to Cognitive Reserve in Healthy Older Adults

Background. Physical and cognitive impairments are two of the most prevalent age-related conditions, with evidence that both factors interact prior to or concurrently with the earliest detectable stages of cognitive impairment. Cognitive reserve (CR) allows an individual to cope more successfully with age-related brain and functional changes and is associated with better cognitive function and reduced risk of cognitive decline. However, it remains unclear to date the specific roles of individual markers of CR, and whether or not this relationship is modified by genetic risk (ApoE-4 genotype) and/or physical function. Method. We assessed cognitive functioning (global cognition, psychomotor speed, language, verbal memory, executive function) in 130 healthy older adults (43.1% males, 56.9% females, ranging in age from 60 to 96). We measured physical function using the Physical Performance Test (PPT) & Timed Up and Go (TUG) tests. CR is represented by years of education, estimated premorbid verbal intelligence (AMNART), and occupational complexity across three levels (with Data, People, and Things). Data was analyzed using a series of hierarchical multiple regression models. Results. Estimated premorbid verbal intelligence contributed independently to global cognition, language, executive function, and verbal memory, while years of education and occupational complexity with data significantly contributed to the prediction of executive function only. Higher physical functioning enhanced the protective effect of estimated verbal intelligence on language. The presence of the ApoE-4 genotype significantly reduced the protective effects of occupational complexity with people on psychomotor speed, and marginally on global cognition. In contrast, the protective effects of occupational complexity with things on global cognition, language, and executive functioning was enhanced in individuals who are ApoE-4 carriers. Conclusion. Findings suggest that cognitive reserve represents a combination of factors that independently determine the threshold for competence within specific cognitive domains, and that these relationships may differ based on physical function and genetic risk. This investigation has the potential to shed light on various factors that can either increase or decrease risk of cognitive decline and highlight the need for cognitive and physical intervention in at-risk older adult populations