Past research has suggested greater levels of cognitive engagement have benefits for neurocognitive function across the lifespan. Greater educational attainment, for instance, has been associated with lower risk of neurodegenerative disease, as well as more intact brain structure, brain function, and cognitive function in both cross-sectional studies (Arenaza-Urquijo et al., 2013, Brickman et al., 2011, Chen et al., 2019, Cox et al., 2016, Foubert-Samier et al., 2012, Herrera et al., 2002, Le Carret et al., 2003, Mukadam et al., 2019, Stern et al., 1994, Teipel et al., 2010) and longitudinally over time (Chodosh et al., 2002, Christensen et al., 1997, Kramer et al., 2004, Montemurro et al., 2023, Valenzuela and Sachdev, 2006).

Furthermore, there is also a breadth of evidence suggesting education may significantly contribute to cognitive reserve, the ability to maintain cognitive function in the presence of age- or disease-related brain changes (Stern, 2009). For example, higher education has been associated with a weaker relationship between brain pathology and cognitive function (Bennett et al., 2005, Bennett et al., 2003, Rentz et al., 2010), and when controlling for measures of clinical severity, higher education is associated with greater deficits in cerebral blood flow in patients with probable AD, suggesting education protects against clinical manifestations of neuropathological damage (Stern et al., 1992). The mechanisms underlying the contribution of educational attainment to cognitive reserve are thought to be related to engagement in cognitively stimulating activities, which may increase synaptic density and plasticity, and promote neurogenesis that protects against and/or compensates for age-related changes in brain structure and function (Baldivia et al., 2008, Sale et al., 2014). Although education is among the most commonly studied proxies of cognitive reserve, several studies have suggested educational attainment is limited in its use as a measure of cognitive reserve, given the influence of socioeconomic and cultural factors in acquisition of formal education (Manly et al., 2003), and evidence that the protective role of education in cognitive reserve may be less consistent in highly educated samples, whereas early childhood education may confer greater benefits for later neurocognitive function (Christensen et al., 2006, Raz et al., 2010). Furthermore, cognitive function is significantly impacted by childhood cognitive experiences outside of formal education, including parental education (Kaplan et al., 2001, Rogers et al., 2009) and childhood stimulating cognitive milieu (Everson-Rose et al., 2003), indicating an important role for non-academic childhood cognitive engagement in neurocognitive function during adulthood.

Given evidence that the role of education in neurocognitive function may be driven by greater early engagement in cognitive activity, and the limitations of using education as a proxy for cognitive reserve, a measure of childhood cognitively stimulating activities (CSA) may serve as an alternative reflection of reserve acquired during early life. Cognitively stimulating environments have been shown to increase neurogenesis and factors related to neuroplasticity, which strengthen resilience against age- and disease-related pathological brain changes (Brown et al., 2003, Stern, 2009, Valenzuela and Sachdev, 2009). Several studies have provided evidence that greater levels of CSA during adulthood, such as reading books and newspapers, playing games and puzzles, or visiting museums, are associated with better cognitive performance across multiple domains (Wilson et al., 2003), as well as significantly reduced risk of Alzheimer’s disease, dementia, and mild cognitive impairment, and lesser decline in cognitive function over time (Wilson et al., 2007, Wilson et al., 2002b, Wilson et al., 2002a). Research has also shown that CSA during adulthood contributes to cognitive reserve over and above the effects of formal education: controlling for clinical severity and formal education, individuals who engage in more cognitive activities have a greater degree of cerebral blood flow deficits, suggesting cognitive stimulation protects against the negative effects of brain pathology (Scarmeas et al., 2003).

Although there is significant evidence suggesting adult engagement in CSA is beneficial for neural and cognitive performance and may protect against age- or disease-related decline, few have tested whether greater CSA engagement during childhood contributes to cognitive reserve that is protective later in life. Given that early childhood education is thought to build brain and cognitive reserve, whereas more advanced levels of education appear to provide less significant benefits, it is possible that CSA during childhood may be a more appropriate measure, compared to adulthood CSA or childhood education that is inseparable from overall education, of the effects of early cognitive engagement on later-life neural and cognitive functioning.

The current study aimed to test whether CSA during childhood moderates the association between brain structure and cognitive performance cross-sectionally, and between longitudinal changes in brain structure and changes in cognitive performance over an average of 5 years in healthy adults. We hypothesized that greater engagement in childhood CSA would attenuate the relationship between brain structure and cognitive function, reflecting a protective role of CSA against neurocognitive decline.