Why better sleep today supports a healthier brain tomorrow

We often focus on food, exercise and supplements when it comes to “brain health”. But could sleep be the most powerful (and overlooked) tool for protecting your memory and long-term cognitive function?

Here’s why improving your sleep now could reduce dementia risk later – and how nutrition can support better sleep and brain health.

Sleep and dementia

Sleep isn’t just a ‘downtime’ during the night. It’s when the brain performs essential housekeeping tasks that support memory, learning, and long-term brain health. During deep sleep (also known as slow-wave sleep), the brain’s glymphatic system — similar to the body’s lymphatic system — clears waste products such as amyloid beta, a protein known to accumulate in Alzheimer’s disease.

When sleep is consistently interrupted or shortened, this clearance process becomes less effective. Over time, this can contribute to inflammation, memory decline, and changes in brain structure.

Poor or insufficient sleep also disrupts key hormones that regulate appetite, metabolism, and stress. Even a few nights of reduced sleep can lower leptin (the hormone that signals fullness) and increase ghrelin (the hunger hormone), increasing hunger and cravings for energy-dense foods.

Sleep loss also elevates cortisol, the body’s primary stress hormone, which can promote increased appetite, fat storage (particularly around the abdomen), and higher blood glucose levels.

What does research tell us?

• Short sleep duration of less than 7 hrs is linked to higher dementia risk in adults aged under 70 years, but lower risk in those 70 years and older.
• Poor sleep quality is linked to faster brain ageing, impaired concentration, mood changes and higher dementia risk.
• Both poor sleep quality and abnormal sleep duration (both too short and too long) may be linked to an increased risk of dementia

A major study from Monash University found that even small declines in deep sleep can meaningfully increase dementia risk. Researchers tracked adults over 60 years old for 17 years and discovered that each 1% loss of deep sleep per year was linked to a 27% higher risk of developing dementia, even after accounting for age, genetics, and medication use.

As deep sleep naturally declines with age, this research highlights just how important it is to protect and prioritise high-quality sleep as a modifiable lifestyle factor for long-term brain health.