Abstract
The oldest-old subjects represent the fastest growing segment of society and are at high risk for dementia with a prevalence of up to 40%. Lifestyle factors, such as lifelong participation in cognitive and leisure activities, may contribute to individual cognitive reserve and reduce the risk for cognitive impairments. However, the neural bases underlying cognitive functioning and cognitive reserve in this age range are still poorly understood. Here, we investigate spectral and functional connectivity features obtained from resting-state MEG recordings in a cohort of 35 cognitively normal (92.2 ± 1.8 years old, 19 women) and 11 cognitively impaired (90.9 ± 1.9 years old, 1 woman) oldest-old participants, in relation to cognitive traits and cognitive reserve. The latter was approximated with a self-reported scale on lifelong engagement in cognitively demanding activities. Cognitively impaired oldest-old participants had slower cortical rhythms in frontal, parietal and default mode network regions compared to the cognitively normal subjects. These alterations mainly concerned the theta and beta band and partially explained inter-subject variability of episodic memory scores. Moreover, a distinct spectral pattern characterized by higher relative power in the alpha band was specifically associated with higher cognitive reserve while taking into account the effect of age and education level. Finally, stronger functional connectivity in the alpha and beta band were weakly associated with better cognitive performances in the whole group of subjects, although functional connectivity effects were less prominent than the spectral ones. Our results shed new light on the neural underpinnings of cognitive functioning in the oldest-old population and indicate that cognitive performance and cognitive reserve may have distinct spectral electrophysiological substrates.
Highlights
The oldest-old population, including individuals aged 85–90 years and older, is the fastest growing segment of Western societies (Corrada et al, 2010; Legdeur et al, 2018)
We investigated the spectral and functional connectivity profiles of MEG data recorded in 35 cognitively normal (CN) and 11 Cognitively Impaired (CI) oldest-old subjects
By definition CI subjects had significantly lower Mini-Mental State Examination (MMSE) total [F(1, 42) = 60.73, p < 10−9] and CERAD total [F(1, 42) = 19.15, p = 0.000073] scores, indicating overall cognitive impairment and reduced episodic memory performances compared to CNs, when taking into account the effects of age and gender
Summary
The oldest-old population, including individuals aged 85–90 years and older, is the fastest growing segment of Western societies (Corrada et al, 2010; Legdeur et al, 2018). The number of oldest-old is estimated to increase fivefold in the coming decades, resulting in 77 millions of oldest-old individuals worldwide by 2050 (United Nations, Department of Economic and Social Affairs, Population Division, 2019) Many of these individuals will suffer from cognitive impairments and dementia, with a dementia prevalence of up to 40% in this age range and major implications for public health and society (Bullain and Corrada, 2013; Yang et al, 2013). The identification of dementia’s neuropathological substrate becomes increasingly challenging with age (Yang et al, 2013) This is due to an increasing prevalence of Alzheimer’s and cerebrovascular pathologies (the most common causes of dementia) among non-demented oldest-old individuals (Wharton et al, 2011; Paolacci et al, 2017; Legdeur et al, 2019), and to a more frequent co-occurrence of multiple dementia-related pathologies (Corrada et al, 2012; James et al, 2012). The neural underpinnings of cognitive functioning and history of lifelong engagement in cognitive activities in the oldest-old population are not clear
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