The heart, metabolism and brain share many risk factors. We sort out the podcast episode and add the studies: what’s established, what’s still open.

In episode 013 of the podcast “die gesunde unterhaltung”, host Tom talks for almost three hours with Dr Manuel Puntschuh, Aeon’s Chief Medical Officer. He’s a specialist in general internal medicine and used to work as a senior physician in an emergency department. You should know that he’s part of Aeon when you hear his take. The episode is in German. You can find it on Apple Podcasts and Spotify.

The conversation jumps between many topics. This article puts three of them in order and sets the studies next to them: insulin resistance, the heart and blood vessels, and dementia. That way you can read up on what’s established and what’s still open. There’s a short version in the article on dementia risk factors. You don’t need to have heard the episode to follow this text.

Topic in the episode Where to find it here
The heart and blood vessels Section “The heart and blood vessels: the process starts early”
Metabolism Section “Metabolism: what happens before the diagnosis”
Dementia Section “Dementia: what’s established and what’s still open”
Measuring and making sense of it Section “What you can take from this”

The episode also touches on cancer screening, hormone therapy, medication and genetics. We’ve left these topics out on purpose, because they involve treatment decisions that belong in a conversation with your doctor.

The heart and blood vessels: the process starts early

A heart attack feels like a sudden event. Behind it there’s usually atherosclerosis: deposits and changes in the artery wall that build up over years (Ference et al., 2017).

A US autopsy study (Strong et al., 1999) shows how early this starts. In 15- to 19-year-olds, the researchers found changes in all the aortas they examined and in more than half of the right coronary arteries. That doesn’t mean a heart problem at that age. It shows that the process begins long before any symptoms.

A heart attack is the late stage of a long process

Schematic, from top to bottom over decades.

YOUTH First changes Autopsy study: 15- to 19-year-olds already showed changes in the artery wall. DECADES The process runs quietly The changes build up, often without symptoms. Duration counts. LATER Heart attack or stroke The event is the late stage of a long process.
Schematic illustration based on Strong et al. (1999) and Ference et al. (2017), not patient data.

That’s why, with LDL cholesterol, it’s not only how high the value is that matters, but also how long it stays high. A consensus statement from the European Atherosclerosis Society (Ference et al., 2017) reviewed more than 200 studies with more than 2 million participants. Risk rises with the level of LDL exposure, and the effect grows with the duration of exposure. The authors state that LDL causes atherosclerotic cardiovascular disease.

LDL isn’t the only factor. The INTERHEART study (Yusuf et al., 2004) compared around 12,500 people with a first heart attack to around 14,600 people without one, in 52 countries. Nine modifiable factors accounted, statistically, for around 90% of heart attack risk in the population among men and 94% among women, including smoking, blood fats, high blood pressure and diabetes.

Metabolism: what happens before the diagnosis

Insulin is a hormone made by the pancreas. It helps sugar move from the blood into the cells. In insulin resistance, the cells respond less strongly to that signal. The body compensates and produces more insulin.

This development starts long before a diabetes diagnosis. In the British Whitehall II cohort (Tabák et al., 2009), insulin sensitivity in people who later developed type 2 diabetes was already falling in the five years before diagnosis. Insulin production first rose and then fell, and fasting blood sugar only rose steeply in the last three years. The authors found changes up to six years before diagnosis. Blood sugar alone therefore only reveals this development late.

How insulin resistance develops

Schematic sequence, from top to bottom over years.

FIRST Weaker signal Cells respond less strongly to insulin. THEN More insulin The body compensates. Blood sugar often stays unremarkable. LATER Compensation no longer enough Blood sugar rises. Type 2 diabetes becomes possible.
Schematic illustration, not patient data.

You can measure this in the blood. The usual tests are fasting blood sugar and HbA1c, which reflects average blood sugar over the past few months. Fasting insulin can be added. From fasting blood sugar and fasting insulin you can calculate HOMA-IR, an estimate of insulin resistance (Matthews et al., 1985). Fasting insulin and HOMA-IR come up in the episode too. What a value means for you is something your doctor puts into the bigger picture. Not every routine check includes all of these values.

Dementia: what’s established and what’s still open

The Lancet Commission on dementia published its latest report in 2024 (Livingston et al., 2024). It names 14 risk factors that can be influenced over the course of a life. The calculation behind it: up to 45% of dementia cases could in theory be prevented or delayed if all 14 factors were eliminated. The figure doesn’t say that a healthy lifestyle means you won’t get dementia. And it doesn’t say that one of these factors means you will. It shows how much room there is overall.

The table groups the report’s 14 factors by theme. The grouping is ours, not the report’s.

Group Factors
Blood vessels and metabolism High blood pressure, high LDL cholesterol, excess weight, diabetes, physical inactivity
Senses Hearing loss, untreated vision loss
Habits and environment Smoking, heavy drinking, air pollution
Mind and everyday life Depression, social isolation
Other Less schooling, head injuries

Context

Several of the factors concern blood vessels and metabolism: blood pressure, blood fats, weight and blood sugar.

Diabetes is one of the Commission’s 14 factors. A review in Nature Reviews Neurology (Arnold et al., 2018) summarises what’s known about insulin signalling in the brain. It describes how type 2 diabetes and Alzheimer’s disease overlap in risk factors, comorbidities and possible mechanisms, and it defines the term brain insulin resistance: brain cells then respond less strongly to insulin than they should.

Whether type 2 diabetes and Alzheimer’s are parallel ageing processes or are linked by a shared mechanism is still open. Some experts therefore call Alzheimer’s “type 3 diabetes”. That’s a metaphor and a hypothesis, not a diagnosis.

The link between metabolism and the brain is plausible. That insulin resistance causes dementia hasn’t been proven.

For you, that means you don’t have to wait for the question of cause to be settled. The factors in the Commission’s report, from blood pressure to cholesterol, can be looked at independently of it.

What you can take from this

If blood vessels, metabolism and the brain share many risk factors, it’s worth looking at the values that can be measured. A single value is a snapshot. The trend over the years tells you more, because exposures such as high LDL cholesterol carry more weight the longer they last (Ference et al., 2017). Measuring more isn’t automatically better. The episode also mentions that measuring a lot can leave you unsettled. What helps is what means something and what you can act on.

The Commission’s report and the studies above describe risk factors, not recipes. Still, they point to questions you can ask at your GP practice.

  • Blood pressure. It’s one of the Lancet Commission’s 14 factors. Get it measured, even if you feel well.
  • Blood sugar and cholesterol. Ask about fasting blood sugar, HbA1c and LDL cholesterol. For fasting values, you’ll come to the blood draw after several hours without eating. The practice will tell you exactly how long.
  • Smoking. Smoking appears on both lists, for the heart and for the brain. If you’d like to stop, your GP practice can support you.
  • Exercise. Physical inactivity is on the list. What helps is what you can keep up long term, not what looks best on paper.
  • Hearing and vision. Hearing loss and untreated vision loss are also among the Lancet Commission’s factors. A hearing test and an eye test are therefore worthwhile appointments.

None of these points is a guarantee. Together they give you a picture of where you stand. And you can compare a picture over the years.

The short version

Laid down early. Atherosclerosis can begin in adolescence, long before any symptoms.
Duration counts. With LDL cholesterol, it’s not only the level that matters but also the time.
Early in metabolism. In people who later developed type 2 diabetes, insulin sensitivity and insulin production changed years before diagnosis.
Shared factors. The heart, metabolism and brain share many risk factors. Statistically, up to 45% of dementia cases are linked to 14 factors.
Cause still open. Whether insulin resistance in the brain causes dementia or just goes along with it isn’t settled.

Conclusion

The heart, metabolism and brain aren’t separate building sites. Many risk factors overlap, and most can be measured and discussed. How far insulin resistance in the brain contributes to dementia is still being researched. That blood pressure, blood fats, weight, exercise and blood sugar keep turning up in the research is, however, well documented. You don’t have to do everything perfectly. Knowing where you stand is enough for a start.

If you’d like a broader picture of your health: the Aeon check-up combines whole-body MRI and blood markers in one appointment. It isn’t a dementia test and doesn’t diagnose dementia.

Book a scan Whole-body MRI and blood markers in one appointment.

Frequently asked questions

Can a blood test detect dementia?

No. Values such as fasting blood sugar, HbA1c or cholesterol tell you something about metabolism and blood vessels, but not whether someone has dementia. If you or a family member notices memory problems, your GP practice is the first port of call. From there, you can be referred to a memory clinic if needed.

Is Alzheimer’s really “type 3 diabetes”?

That’s a hypothesis, not a diagnosis. Behind it is the idea of insulin resistance in brain cells. The review by Arnold and colleagues (2018) describes overlaps between type 2 diabetes and Alzheimer’s and leaves open whether they’re parallel ageing processes or linked cycles.

When does atherosclerosis begin?

A US autopsy study found changes in the aorta and in more than half of the right coronary arteries in 15- to 19-year-olds (Strong et al., 1999). That doesn’t mean a heart problem at that age. It shows that the process starts long before any symptoms.

Which values say something about insulin resistance?

The usual ones are fasting blood sugar and HbA1c. You can also have fasting insulin measured, and together with fasting blood sugar it gives you the HOMA-IR (Matthews et al., 1985). Not every routine check includes all of these values. Ask your practice which ones it offers.

Do the episode or this article replace a conversation with my GP?

No. Both help you make sense of things, but neither is a diagnosis or a treatment recommendation. If you have questions about your health, your GP practice is the first port of call.

Sources