Contrary to fears of 'digital dementia,' some research indicates that people over 50 who regularly use digital devices experience lower rates of cognitive decline. While the causal link is still being studied, it challenges the narrative that screen time is inherently harmful for older minds.

A 40-year longitudinal study of Swedish women found a powerful correlation between mid-life fitness and late-life cognitive function. Women who were categorized as "high fit" in their 40s experienced, on average, nine more years of good cognitive health in their 80s compared to their low-fit counterparts.

To truly train the brain, engage in "dual-tasking" by imposing a cognitive load (like counting backward by threes) during physical activity. This stress forces the brain to create new neural pathways, building resilience against age-related cognitive decline.

Sensory decline, like hearing loss or cataracts, is linked to a higher risk of dementia, likely due to reduced brain stimulation and social engagement. However, this risk appears to be reversible. Interventions like cataract surgery or hearing aids restore sensory input, effectively eliminating the added risk.

A long-term study found many nuns had brains full of Alzheimer's plaques post-mortem, yet displayed no cognitive decline in life. Their constant social responsibilities and interactions acted as a continuous mental challenge, building new neural pathways that bypassed the damaged areas.

Meta-analyses of interventions in older adults show that learning complex dances like ballroom or line dancing has the greatest positive effect on cognitive function. This is likely due to the rich combination of physical activity, skill acquisition, social interaction, and musical timing.

It's possible to have a brain full of amyloid plaques (a hallmark of Alzheimer's) yet show no cognitive decline. This is due to 'cognitive reserve,' the brain's ability to withstand damage. Building this reserve through activities like reading, writing, and exercise is a key defense.

Performing intense VO2 max training, like the "Norwegian 4x4" protocol, three times a week for 5-6 months can induce neuroanatomical changes in the brain that may last for up to five years. This offers a potential protective effect against cognitive decline and Alzheimer's.

Dellis's primary motivation for memory training isn't winning or practical recall, but building a cognitive “tool set” for old age. Inspired by his grandmother's Alzheimer's, he views it as a way to potentially prolong mental function and fight cognitive decline, a more profound goal than simply remembering trivia in the digital age.