Differential effects of brain maintenance and cognitive reserve on age-related cognitive decline

Abstract

Background: While cognitive decline has been frequently reported in aging research, moderating factors for cognitive changes in healthy aging have been inconclusive. This study evaluated 5 year changes in four cognitive abilities and the potential moderation of age and cognitive reserve (CR) factors on cognitive changes. Methods: Participants included 254 healthy adults initially aged 20 to 80 years. Six tasks estimated each of the four abilities: fluid reasoning, processing speed, memory and vocabulary. The proxies for CR included years of education and IQ. Cognitive changes and moderating factors were examine using multiple indicator latent change score model. Change point analysis pinpointed inflection points after which cognitive changes accelerated. Results: There was significant decline over five years in fluid reasoning, processing speed and memory, with age moderation such that older age was associated with steeper decline. Accelerated decline was observed earlier for reasoning and speed, at ages 58 and 59 years respectively, than for memory, at age 70 years. Vocabulary continued to improve until reaching peak performance at 67 years. For moderation of cognitive changes by CR proxies, while education did not show significant moderation, higher IQ was associated with reduced 5-year decline in reasoning and memory but not processing speed. CR moderation effect was found to be independent of mean cortical thickness. Conclusions: Using a robust statistical model to estimate the latent change in four cognitive abilities over 5 years, the results showed that cognitive reserve rather than brain maintenance is the potential mechanism underlying IQs protective effect on cognitive decline.

Leisure activity engagement across adulthood predicts cognitive change after five years: Do gender and age matter?

“…Critically, LA protective benefits have been observed in several cognitive domains, such as global cognition, language, executive functions (Wang et al, 2013;Yates et al, 2016), speed processing (Ghisletta et al, 2006;Lovden et al, 2005;Small et al, 2012;Yates et al, 2016) and episodic memory (Richards et al, 2003;Small et al, 2012;Wang et al, 2013;Yates et al, 2016). A novel finding from our study is that LA was not only associated with less cognitive decline but also with better performance on vocabulary or crystallized intelligence, as this domain has been shown to improve over time (Gazes et al, 2021;Salthouse, 1998Salthouse, , 2010. Interestingly, our finding was consistent across these cognitive domains with effect sizes ranging from medium (vocabulary) to large (reasoning and speed).…”

“…At baseline and follow-up, participants underwent a comprehensive neuropsychological (out-of-scanner) evaluation and performed several computerized cognitive tasks during the MRI exam (Gazes et al, 2021;Habeck et al, 2016;Salthouse et al, 2015). As per a previous study from our group (Salthouse et al, 2015), 12 measures were selected based on a factor analysis reflecting four domains: reasoning, processing speed, memory, and vocabulary.…”

“…As described previously (Gazes et al, 2021;Habeck et al, 2016), the in-scanner computerized tasks were comprised of twelve measures reflecting the same cognitive domains selected from the neuropsychological battery. Details on MRI acquisition are described in Supplementary Material.…”

“…We used a multiple indicator latent change score model (LCSM) (Kievit et al, 2018) to generate cognitive scores at baseline and follow-up, as shown in Figure 2 (Gazes et al, 2021), but without covariates. For additional details on the coefficients associated with each of the latent variables, see Table 1 on Supplementary material.…”

“…As per a previous study from our group (Salthouse et al, 2015), 12 measures were selected based on a factor analysis reflecting four domains: reasoning, processing speed, memory, and vocabulary. Previous works indicate that reasoning, speed, and memory decline with cognitive aging, while vocabulary tends to increase or remain stable over time (Gazes et al, 2021;Habeck et al, 2016;Salthouse, 2004;Salthouse, 2009Salthouse, , 2019Stern et al, 2014). Each cognitive domain included three measures: reasoning: Wechsler Adult Intelligence Scale (WAIS-III) Matrix Reasoning, Letter-number Sequencing, and Block Design test (Wechsler, 1997); speed: WAIS-III Digit-symbol (digit coding test), Stroop Color Naming Test (Golden, 1975), and Trail Making Test (TMT)-A (time) (Reitan, 1978); memory: Selective Reminding Test (SRT); last trial, continuous long-term retrieval and last retrieval (Buschke & Fuld, 1974); vocabulary: WAIS-III Vocabulary test, the Wechsler Test of Adult Reading (WTAR) (Wechsler, 2001), and the American National Adult Reading Test (AMNART) (Grober et al, 1991).…”