The effect of baseline and longitudinal cognitive reserve on memory ageing in middle and older age adults over a 12‐year period

Abstract

AbstractBackground‘Cognitive reserve’ (CR) refers to a model of active protection against cognitive decline conferred by the adaptability of one’s cognitive processes. Research on life‐course accumulation of reserve and impact of factors like gender is limited. We examined long‐term effects of CR on episodic memory in two population‐based cohorts.MethodsParticipants consists of two cohorts from the PATH Through Life project with 12 years (4 waves) of follow‐up, with had an average of 14.6 and 13.9 years of education. The mid‐life cohort (MA) was aged 40‐44 at baseline (mean age 42.6, 52.7% self‐reported female;47.3% male, 0% other gender, N = 2513) and the older cohort (OA) was aged 60‐64 at baseline (mean age 62.5, 48.1% female, 49.9% male, 0% other gender, N = 2403). A baseline composite CR measure included education, occupational complexity, and cognitive and social engagement measured by the RIASEC scales. Episodic memory (Immediate and delayed recall) was assessed with a 16‐word list. Multilevel models adjusting for baseline age, self‐reported gender, race, APOE and non‐English speaking background; evaluated the effect of both baseline and longitudinal change in CR on the longitudinal change in episodic memory.ResultsOn average, women performed better than men on the episodic memory tasks. Compared with participants in the top tertile of CR, those middle and lowest tertiles had larger decline in episodic memory in both MA and OA. Interactions with APOE were not significant, but among those with medium (model derived beta weights 95% CI: 0.35 (0.01‐0.69)) and high (0.48(0.07‐0.90)) CR, women showed less decline than men. Each component of CR (education, occupational complexity, and RIASEC) was protective against decline in immediate and delayed recall. Increase in RIASEC score over time was protective (MA (0.05, (0.04‐0.07); OA 0.13, (0.11‐0.16)) with a larger effect seen in OA.ConclusionThe current study demonstrated protective effects against cognitive decline for all types of CR measured in both middle and older‐age groups. Increases in CR over time were also protective. The benefits of CR were highest for older women who comprise the age and gender group at most risk of Alzheimer’s disease, indicating the need for CR interventions.