How Does Muscular Strength Lower Dementia Risk?

TL;DR

Strength is one of the strongest modifiable factors linked to dementia. Comparing the top 10% of people by strength with the bottom 10% shows about a 70% reduction in both incidence and mortality from all-cause dementia. Possible reasons include neuromuscular stimulation from novel movement, better blood sugar regulation, myokines such as BDNF, and less systemic inflammation.

Transcript

I'd like to talk a little bit about one of the strongest associations I've ever seen with mitigating risk which is strength um so the you know this is often demonstrated with simple measurable things like grip strength but I don't think it's that the strength of your grip and the ability to open a jar is particularly important it's just that you kn... Read More

Key Insights

• Muscular strength is one of the strongest associations with lower dementia risk. The top 10% of people by strength show about a 70% reduction in both incidence and mortality from all-cause dementia compared with the bottom 10%.
• Grip strength is useful mainly as a proxy for overall strength. A very strong grip matters less for opening jars than for what it signals: the ability to carry heavy things, which requires strength along the whole body chain.
• The link between strength and brain health is not just confounding by general health. People in their 70s on a basic resistance training program improved in white matter connectivity on MRI scans and on tests of cognitive function.
• Novel movement acts as a direct neuromuscular stimulus. Recruiting motor fibers and learning a motor skill is a cognitive stimulus in itself, prompting the brain to form new connections and driving plasticity.
• Muscle is an important glucose sink. Having more muscle and moving it increases glucose flux and helps regulate blood sugar, which matters because prediabetes and type 2 diabetes are significant risk factors for cognitive decline and dementia.
• Myokines are substances released by muscle tissue that may support brain function. Examples mentioned include IGF-1, VEGF and brain-derived neurotrophic factor (BDNF), which may act as survival factors that keep neurons alive.
• Exercise is anti-inflammatory through a hormetic process. Chronic inflammatory conditions are associated with increased dementia risk, and physical activity lowers systemic inflammation, which may protect the brain.
• Strength and fitness are worth building even setting aside lifespan. Peter Attia argues that even if they shortened life by six months, they would still be worth it for quality of life in the final decade, when weakness and pain limit daily activities.

Questions & Answers

Q: How much does muscular strength reduce dementia risk?

When the top 10% or so of people by strength are compared with the bottom 10%, there is about a 70% reduction in both incidence and mortality from all-cause dementia. Tommy Wood says this places strength near the top of the list of factors people have some control over. He notes that someone at the bottom cannot reach the top within a year, but strength is something everyone can work toward over a lifetime.

Q: Why is grip strength used to measure dementia risk?

Grip strength is a simple, measurable test, but its value is not about how well someone can open a jar. It is a good proxy for overall strength. People with a very strong grip can carry very heavy things, which requires strength all the way up and down the body's chain. High or low grip strength therefore reflects the strength of the whole body rather than the hand alone.

Q: Is the link between strength and dementia just because healthier people are stronger?

Tommy Wood says confounding explains only part of it. People often assume healthier people are simply stronger, but there is good evidence that strength training itself has an effect. When people in their 70s follow a very basic resistance training program, they show improvements in white matter connectivity on MRI scans and on tests of cognitive function. Some of the association reflects general health, but there are many additional effects on top of that.

Q: How does novel movement help the brain?

Novel movement is a direct neuromuscular stimulus. When a person learns or performs a new motor skill, the recruitment of motor fibers acts as a cognitive stimulus. This prompts the brain to create new connections and drives plasticity. Tommy Wood lists this as the simplest explanation for why strength training benefits cognition, because learning and performing movements trains the brain as well as the muscles.

Q: How does muscle mass affect blood sugar and dementia risk?

Muscle is an important glucose sink. The amount of muscle a person has, and how much they move it, increases glucose flux and helps regulate blood sugar. This matters for brain health because prediabetes and type 2 diabetes are significant risk factors for cognitive decline and dementia. Building and using muscle may therefore lower dementia risk partly through better blood sugar control.

Q: What are myokines and how do they support brain function?

Myokines are substances released by muscle tissue when muscles are used, and Tommy Wood describes them as a still-exploding area of research. Examples include IGF-1, VEGF and brain-derived neurotrophic factor (BDNF). These may support neuronal function and act as survival factors that help keep neurons alive. Myokines are one of several possible routes by which moving muscles benefits the brain.

Q: Why does exercise reduce inflammation linked to dementia?

Exercise is anti-inflammatory through a hormetic process. Chronic inflammatory conditions can be associated with increased dementia risk, and physical activity decreases systemic inflammation. Tommy Wood groups this with neuromuscular stimulation, blood sugar regulation and myokines as mechanisms that likely all play a role. He does not know which is most important, and says it matters less than knowing strength training works and can be started at almost any stage.

Q: Why is strength training worth it even if it does not extend lifespan?

Peter Attia argues that even if strength, muscle mass and cardiorespiratory fitness did not add a single day to life, or even shortened it by six months, they would still be worth it for quality of life. This is especially true in the final decade, which he calls the marginal decade. At that stage poor movement, pain and low strength limit nearly everything people enjoy, from playing with their kids to going for a walk or carrying out basic daily activities.

Summary & Key Takeaways

• Strength ranks near the top of controllable factors linked to dementia. Comparing the strongest 10% of people with the weakest 10% shows roughly a 70% reduction in both dementia incidence and mortality. Grip strength is commonly measured, but it mainly works as a proxy for strength throughout the body.

• Tommy Wood rejects the idea that the strength-dementia link is just confounding by overall health. Resistance training trials in people in their 70s improved white matter connectivity on MRI and cognitive test scores, showing that training itself can change brain outcomes at practically any stage of life.

• Several mechanisms likely work together: novel movement stimulates brain plasticity, muscle acts as a glucose sink that helps regulate blood sugar, myokines like IGF-1, VEGF and BDNF may support neurons, and exercise lowers systemic inflammation. These effects are probably additive, if not synergistic, which may explain why strength is so beneficial.