Modifiable lifestyle factors for cognitive health: The role of Cognitive Reserve and Motor Reserve

Lifestyle factors such as cognitive, social, and physical activities have been examined in the literature as potential enhancers of cognitive health in healthy individuals and those with pathological conditions. The knowledge, skills, and experiences acquired throughout lifespan contribute to Cognitive Reserve (CR), which refers to the ability to utilise available brain resources flexibly and efficiently. It is commonly observed that individuals with higher CR tend to have more efficient brain networks that enable them to cope with pathology through compensatory mechanisms. This compensation is attributed to the accumulation of cognitive resources gained through prolonged exposure to stimulating activities during education, occupation, and leisure activities. Furthermore, Physical Activity (PA) has recently been explored due to its potential to prevent age-related diseases and maintain or enhance cognitive functioning in healthy individuals. Emerging evidence suggests that PA can improve cognition in healthy adults, reduce the incidence of dementia, and enhance the health of individuals with existing dementia. PA carried out throughout the lifespan may also influence cognition. For instance, the literature shows that PA during teenage may lead to less decline in executive functioning in older age. In line with this evidence, we hypothesised a Motor Reserve (MR), a flexible and dynamic construct that accumulates over the years, possibly compensating for age-related cognitive decline. MR encompasses not only physical exercise and structured activities typically performed to improve and maintain physical fitness but also incidental PA, which includes unstructured daily activities that involve a metabolic cost above the baseline, such as walking, housekeeping, and workplace activities. Considering this background, this thesis investigates the relationship between Cognitive Health, Cognitive Reserve, and Motor Reserve. We hypothesised that the greater CR and MR, the better the Cognitive Health. We explored these relationships in diverse populations, including healthy adults, fragile individuals (Oldest-Old and Subjective Cognitive Decline), people with neurological disorders (Multiple Sclerosis) and individuals with genetic conditions (Intellectual Developmental Disability). In addition, we integrated the concept of CR within the neuropsychological assessment by developing new cognitive tests that consider CR to generate cut-offs, guaranteeing a more accurate interpretation of examinees' performance. Investigating the effect of CR and MR on cognitive health in adults, older adults and pathological populations provided guidelines for developing new preventive protocols for cognitive decline and rehabilitation programs for people with existing neurological diseases.