LAUSR

As the global population ages, the number of individuals with clinical Alzheimer’s disease and related dementias (ADRD) is rapidly increasing (Prince et al., 2013). In 2010, the worldwide prevalence of ADRD was 35.6 million people. This number is expected to increase to 115 million people worldwide by the year 2050. The number of people with preclinical Alzheimer’s disease (e.g. evidence of Alzheimer’s disease neuropathology and/or neurodegeneration without cognitive decline on standardizedmeasures) is even higher (Brookmeyer et al., 2018). Unfortunately, there are no disease-altering interventions for ADRD. It is of utmost importance to identify modifiable risk factors that can prevent or delay the onset of ADRD. This is especially true for individuals at high risk of clinical dementia such as individuals who have preclinical Alzheimer’s disease but no cognitive impairment. Delaying the onset of clinical ADRD not only prolongs the individual’s quality of life but can have a significant public health impact. Delaying the onset of clinical ADRD by 5 years may translate to a savings of approximately 500,000 dollars in informal healthcare costs per individual (Zissimopoulos et al., 2014). Therefore, researchers need to work to identify factors that promote resilience against age and disease-related cognitive declines. Cognitive reserve (CR) is an important aspect of resilience. Promoting CR may be important for delaying the onset of clinical ADRD. Discrepancies between detected neuropathology and clinical manifestation are common (Stern, 2009). For example, it is well known that some individuals are able to tolerate significant amounts of accumulated neuropathology yet have relatively spared cognitive functioning. CR is a construct that accounts for these discrepancies (Stern et al., 2018). Someone with higher CR is able to withstand higher amounts of neuropathology while being able to function independently. Importantly, CR is thought to be a fluid construct in that it changes across the lifespan and is a result of experiences that occur throughout the lifespan. The fluid nature of CR is important as it highlights that individuals may potentially be able to increase CR over the course of the entire lifespan. Some important experiences or lifestyle factors that contribute to CR include educational attainment, occupational complexity, engagement in cognitively stimulating activities, engagement in active leisure activities, physical exercise, dietary factors, and lower stress (Satz et al., 2011). Social support is another important factor that is thought to promote CR. Increased social support, such as having more close friends, may contribute to emotional, instrumental, and informational support. This supportmay then promoteCR by reducing stress and promoting healthier lifestyles. Another possibility is that individuals with more social support may spend more time engaging in leisure activities that are thought to promote CR. There have been no studies examining if engagement in leisure activities mediate protective effects of higher social support on declines in cognitive performance. In this important work by Ihle et al. (2019), they present evidence that engagement in leisure activities may mediate the protective association between higher social support on a slower decline in executive function over a 6-year period. Ihle et al. (2019) examined data from the ongoing Vivre–Leben–Vivere (VLV) survey (Ihle et al., 2016). The VLV is a large interdisciplinary study examining the mental and physical health of older adults (aged 65 and older) living in Switzerland. In 2011, participants completed assessments of both social support and leisure activity engagement. Social support consisted of having the individual indicate the number of close friends that they had. Leisure activities captured different domains of activity including cognitive activities, physical activities, and social activities. A total of 18 activities were measured including: going for a walk, gardening, physical exercise, playing sports, going to a restaurant, going to the movies, excursions of 1 or 2 days, vacations 3 days or longer, playing musical instruments, other artistic activities, taking a course, playing card games, doing crossword puzzles, needlework, doing crafts, participation in political activities, volunteering in the community, and going to a sporting event. Executive functioning was then measured at the study baseline in 2011, and again 6 years later in 2017, with the part A and B of the Trailmaking Test. First, the authors considered the association between baseline engagement in leisure activities International Psychogeriatrics (2021), 33:5, 433–435 © International Psychogeriatric Association 2021