A health expert has explained what she claims to be an early warning sign of dementia, which she says can be identified 15 years before a clinical diagnosis. Dr Annette Bosworth appeared on an episode of Steven Bartlett's Diary Of A CEO to discuss the link between insulin and dementia.
Metabolic signs precede cognitive decline
Dr Annette Bosworth, commonly known as Dr Boz, is an internal medicine doctor with over two decades of experience, who helps reverse medical problems through healthy Keto living. She educates the audience on her YouTube platform 'Dr Boz' and is the bestselling author of several books, including 'KetoCONTINUUM: Consistently Keto Diet for Life'.
Dr Annette Bosworth argued that the initial underlying changes leading to dementia can be detected 10 to 15 years before an official diagnosis. However, she specified that these "first signs" are metabolic rather than cognitive.
Insulin resistance and 'brain trash'
Dr Bosworth argued that the earliest warning sign is chronically high insulin levels and insulin resistance. She pointed out that the brain's ability to clear cellular waste becomes impaired, and its energy supply is compromised, decades before a patient ever forgets a name or misplaces their keys.
According to Dr Annette Bosworth, a primary indicator of potential cognitive decline is when a patient begins to struggle with memory in daily life, such as getting lost while driving. She explains that this is a symptom of accumulated "brain trash" and debris resulting from long-term insulin resistance and high insulin levels over many years.
She emphasised that these kinds of 'forgetful' moments are often indications that the brain has been accumulating metabolic 'trash' for up to 15 years. And she says that by the time these symptoms appear, the process is well underway.
She said: "They come into the clinic and they’re already starting to say, 'I was driving the other day, and I got lost'. And when I hear that, we are 15 years too late. It is 15 years of building up trash in that brain, we have to clean out that debris."
Research and biological markers
Two major lines of research from the American Academy of Neurology strongly support the concept that dementia leaves a clear footprint 15 years before an official clinical diagnosis. These include the 15-year pre-clinical work productivity decline (July 2026) and the midlife metabolic link to 15+ years of brain health (August 2026).
Studies show chronically high insulin levels and insulin resistance are strong warning signs for a higher risk of cognitive decline and dementia, rather than direct early symptoms of the condition itself. Research from health groups like the Alzheimer's Society shows that managing blood sugar, eating a healthy diet, and exercising can lower your overall risk of cognitive issues. For more details, you can also read the Type Two Diabetes and Dementia Risk Guide.
Instead of memory tests, Dr Annette Bosworth says that when she’s examining her patients, she looks for early biological markers like a haemoglobin A1C creeping above 5.5, chronic vitamin D deficiency, and an inability of the body to naturally produce morning ketones.
According to Medical News Today, identifying early signs of metabolic and biochemical problems helps doctors spot problems in other body systems well before memory and thinking issues show up. This can help doctors figure out targeted prevention strategies.
While regular medical tests look for brain plaques after damage has already happened, markers like haemoglobin A1C higher than 5.5, long-term vitamin D shortage, and missing morning ketones directly show early metabolic inflexibility and brain inflammation—the root causes that deprive brain cells of what they need and speed up dementia and Alzheimer's disease.
