Bryan Johnson's protocol is based on the concept that each organ ages at its own rate. Identifying an organ's accelerated biological age—like his "64-year-old ear"—allows for targeted interventions that can slow overall aging and prevent related issues like cognitive decline.

The distinction between "diseases of late life" and aging itself is artificial. Conditions like Alzheimer's or most cancers are simply aspects of aging that have been given disease-like names. This unifies them as targets for a single, comprehensive anti-aging medical intervention.

While PET scans show lower glucose uptake in Alzheimer's brains, this may not be due to insulin resistance ("type 3 diabetes"). Studies show these brains can absorb glucose normally when cognitively stimulated. This suggests the issue is a lack of demand from inactive brain regions, not a failed supply mechanism.

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.

Beyond tackling fatal diseases to increase lifespan, a new wave of biotech innovation focuses on "health span"—the period of life lived in high quality. This includes developing treatments for conditions often dismissed as aging, such as frailty, vision loss, and hearing decline, aiming to improve wellbeing in later decades.

Higher education builds "cognitive reserve" by increasing neural connections. This creates a higher physiological baseline, meaning it takes much longer for age-related brain cell loss to manifest as cognitive impairment, a benefit often overlooked in financial ROI debates.

The severity of clinical dementia is not solely determined by neurological damage. Social factors like relationships, environment, and family support—termed "psychosocial reserve"—can be as crucial as neuropathology, explaining why some individuals with significant brain damage remain cognitively intact while others decline rapidly.

Chronic illnesses like cancer, heart disease, and Alzheimer's typically develop over two decades before symptoms appear. This long "runway" is a massive, underutilized opportunity to identify high-risk individuals and intervene, yet medicine typically focuses on treatment only after a disease is established.

The link between hearing loss and Alzheimer's is twofold. Physically, the lack of auditory stimulation causes parts of the brain to atrophy. Psychologically, the inability to hear properly can lead to a negativity bias, where one fills conversational gaps with paranoid thoughts, increasing chronic stress and isolation.