Can Cognitive Decline Be Reversed? | Dr. Tommy Wood | GLS #198

The speaker emphasizes that during acute stress, the brain is 'dunked in adrenaline,' making cognitive regulation (thinking yourself calm) nearly impossible. Instead, he advocates for 'bottom-up' physiological approaches. Breathwork, specifically techniques that lengthen exhalation, stimulates the vagus nerve, which is a key component of the parasympathetic nervous system responsible for 'rest and digest' functions. This activation helps to slow heart rate and lower blood pressure. Another simple yet powerful technique is closing one's eyes, which reduces sensory input, particularly visual stressors, and can immediately calm stress-related brain networks. For situations where closing eyes isn't feasible, like for a Formula 1 driver, the 'quiet eye' technique involves purposefully focusing on a target for a few seconds before an action, counteracting the erratic eye movements that stress can induce. These methods provide immediate, tangible ways to manage the body's stress response.

The speaker argues that the health and function of our brains are primarily driven by how we use them. Engaging in complex cognitive activities, such as learning new skills, languages, or musical instruments, directly leads to observable changes in brain structure and volume. He cites studies on London taxi drivers, jugglers, and language learners, showing that the brain's shape and structure can change within months in response to such stimuli. Conversely, when these activities cease, the brain areas can shrink. This concept is tied to 'brain reserve,' which is the amount of brain tissue in the skull. Furthermore, cognitive stimulation can improve glucose uptake in the brain. In early Alzheimer's, decreased glucose uptake is observed, but if the brain is stimulated, it 'asks for more glucose,' demonstrating its capacity to respond. Therefore, continuous engagement in mentally demanding tasks is essential for maintaining brain structure, function, and metabolic health.

Physical activity is presented as a 'physiological imperative' for optimal body and brain function. The speaker details how different types of exercise benefit specific brain structures. Brisk walking, an aerobic activity, has been shown in older adults to improve the size of the hippocampus (critical for memory) and overall fitness. Resistance training, on the other hand, is particularly beneficial for the structure of white matter, which facilitates rapid communication between different brain regions. This is attributed to the release of IGF-1 during resistance training, while aerobic exercise promotes BDNF. The speaker notes that physical activity can also offset some of the negative effects of inadequate sleep, potentially by improving blood pressure, blood sugar, and inflammation, and by enhancing sleep quality itself. This dual benefit underscores the importance of a comprehensive exercise regimen for brain health.

The speaker identifies hypertension and pre-diabetes/diabetes as the two most significant metabolic risk factors for dementia. He defines hypertension as blood pressure above 120/80 mmHg, noting that risk begins to increase above this threshold, and becomes significantly elevated around 130/85 mmHg. He points out that blood pressure medications are one of the few pharmaceutical interventions proven to significantly reduce dementia risk. For blood sugar, a fasting level above 100 mg/dL (pre-diabetes) is associated with a faster rate of cognitive decline compared to normal levels. While some might tolerate higher numbers, the speaker suggests that lower is generally better for brain function, ideally in the low 90s or high 80s. He emphasizes that avoiding the components of metabolic syndrome (elevated triglycerides, blood glucose, blood pressure, wide waistline, low HDL) is crucial, though rarely achieved by the general population.

The speaker addresses alcohol consumption, acknowledging that many seek justification for their current intake. He disagrees with extreme claims that 'any alcohol is bad,' citing methodological issues in some studies. However, he firmly states that alcohol has clear downsides, particularly its negative impact on sleep architecture, causing REM sleep deficits and disrupting thermoregulation during sleep. Based on overall outcomes, brain volumes, and cognitive function, he suggests that averaging less than half a standard US drink per day (equivalent to one or two drinks per week) appears to have no net negative effect on the brain. Exceeding this amount is associated with observable changes in brain structure, reduced cognitive function, and a higher risk of dementia. The occasional drink with friends is likely fine, but regular, higher intake poses a risk.

The speaker acknowledges the critical importance of sleep, noting that consistently sleeping less than six hours per night increases dementia risk. However, he also offers a nuanced perspective, particularly for those with unavoidable sleep challenges (like new parents). He highlights evidence that physical activity can significantly offset some negative effects of sleep deprivation, potentially by improving blood pressure, blood sugar, and inflammation, and by enhancing the quality of the sleep one does get. He also mentions studies showing that perceived sleep quality can influence next-day performance more than actual sleep, and that the brain can adapt to short-term sleep deprivation, affecting mood more than performance. While not a substitute for consistent good sleep, exercise and even later-life improvements in sleep patterns (e.g., in one's 50s or 60s) can still yield benefits, including reduced pathological burden in the brain.

The speaker references research by Alia Crumb at Stanford, which demonstrates that individuals who are primed to believe stress is enhancing (e.g., by being told it helps performance) exhibit different hormonal profiles when subjected to stressful situations. While cortisol levels may still rise, these individuals also show increased levels of DHEA, a hormone associated with adaptation and recovery. This mindset has been linked to better decision-making under stress and even predicts success in demanding environments like SEAL training. The implication is that consciously reframing one's perception of stress can have immediate and tangible physiological and cognitive benefits.

The speaker introduces a framework, borrowed from Ken Ford, to distinguish between using technology as a 'cognitive orthotic' versus a 'cognitive prosthetic.' An orthotic, like a leg brace, supports and builds upon existing capabilities, requiring active engagement. For example, using an AI to review an essay after one has already put in the effort to write it, helps to expand one's thinking. Conversely, a prosthetic replaces a lost function entirely, like a prosthetic leg. Using AI as a prosthetic means letting it do the thinking for you, which the speaker warns can lead to the atrophy of cognitive skills. He expresses concern about colleagues using AI to 'do their science for them,' observing a 'deskilling in real time.' The key takeaway is that active engagement with the tool, rather than passive reliance, is crucial for maintaining and enhancing brain function.

The speaker, referencing a paper co-authored with Josh Turket and insights from palliative care physician Judel, argues that social connection is a primary driver of cognitive function and a key factor in preventing decline. He highlights that our complex social structure was a major force in human brain evolution, citing Darwin's later work on 'sympathy' (empathy) as crucial for group survival. Studies on social isolation (e.g., simulated Mars trips, Arctic exploration, solitary confinement) show that evolutionarily recent parts of the brain, responsible for complex cognitive functions, are most susceptible to aging and decline during periods of isolation. Furthermore, pro-social behavior (doing things for others) is particularly beneficial, activating the vagus nerve and downregulating stress. Social stress, including perceived social rank changes (like shame), can trigger an evolutionarily conserved shift in immune function, leading to chronic low-grade inflammation if prolonged. This suggests that the quality and quantity of our social interactions directly impact our brain's architecture and physiological well-being.

The speaker explains 'brain reserve' as the amount of brain tissue in the skull, adjusted for skull size. This reserve can be increased by engaging in new, complex cognitive stimuli, such as learning to juggle, new languages, or musical instruments, which can lead to observable changes in brain structure (e.g., visual cortex volume) within months. Just as muscles atrophy without training, brain areas can shrink when not used. However, the brain retains neuroplasticity, meaning it can still adapt and change. Even in early stages of cognitive decline, neurons don't necessarily die but shrink, similar to muscle disuse. This implies that re-engaging these processes through interventions like physical activity, cognitive stimulation, and social connection can lead to recovery of function and even structural improvements, as seen in some resistance training studies reversing white matter hyperintensities. The brain's capacity to respond to these inputs persists until the late stages of dementia, offering a window for intervention and improved quality of life, even if full reversal of Alzheimer's remains controversial.