Cognitive reserve and everyday functioning in cognitively unimpaired older adults: evidence from the CAN-PROTECT study

BACKGROUND: Cognitive reserve (CR) is thought to buffer against the clinical manifestation of dementia, preserving cognitive function despite accumulating pathology. However, less is known about how CR relates to the capacity to independently perform activities of daily living (ADL), particularly among cognitively unimpaired (CU) older adults. Here, we investigated this association. METHODS: Baseline data from 1,571 CU participants (mean age: 64.7±7.6; 81.3% female) from the CAN-PROTECT study were analyzed. A composite CR score was derived from education, occupational complexity, and engagement in cognitively stimulating activities. Functional ability was measured using the Standard Assessment of Global Everyday Activities (SAGEA) scale, capturing cognitive, applied cognitive, instrumental, and basic ADL, and mobility. Negative binomial models examined associations between CR and global and domain-specific ADL, adjusting for age, sex, cognition, behaviour, and physical/sensory limitations. Additional models tested the independent contribution of CR components to functional outcomes. Mediation analyses assessed the effect of CR on quality of life (QoL) through ADL abilities. RESULTS: Higher CR was associated with lower global ADL impairment (count ratio=0.58, 95%CI: 0.36-0.94, p = 0.027), driven by 49% less impairment in applied cognitive ADL (95%CI: 0.26-0.97, p = 0.038). Among CR domains, education showed the most consistent association with lower impairment across all ADL domains and was indirectly linked to better QoL through improved function. CONCLUSIONS: CR, particularly education, may play an important role in supporting functional abilities and QoL among CU older adults. Enhancing CR may be a promising avenue to promote functional independence and healthy aging, even in the absence of cognitive impairment.