Neuroscientists have traditionally focused on the beginning and end stages of brain development: the rapid formation and reduction of neural connections in youth and the decline in older age. “We kind of skipped over middle age,” notes Sebastian Dohm-Hansen, a bioinformatician at University College Cork in Ireland.
The emphasis on extreme changes in brain structure and function has made it easier to study these stages using neuroimaging. In the context of cognitive decline and dementia, Dohm-Hansen points out that significant symptoms often appear after age 60.
However, recent research is delving into the middle-aged brain, uncovering subtle yet important changes between ages 40 and 65. This period is seen as crucial for identifying issues that may arise later.
Ahmad Hariri, a professor of neuroscience at Duke University, likens midlife to the peak of an inverted U-curve. Early life involves brain development, while the later years involve gradual decline. “Targeting midlife is like extending that level section at the top of the curve, to delay the downward trajectory,” Hariri explains.
Key midlife changes, according to a 2024 review by Dohm-Hansen and colleagues, involve connectivity—how neurons communicate over distances and how the brain organizes processing across regions. Connectivity peaks in middle age before declining.
This decline correlates with cognitive abilities, particularly memory. Dohm-Hansen describes middle age as a “turning point” for the brain, presenting an opportunity to detect future issues. However, tracking these changes is complex, as connectivity may increase in some networks to compensate for losses, and individual variations occur.
New methods to detect early signs of cognitive decline and dementia are emerging. One notable approach involves blood-based biomarker tests, which can identify misfolded amyloid-beta and tau proteins associated with Alzheimer’s disease—often before symptoms arise (source).
These tests may eventually become part of routine screenings, though they are already available to consumers. Neurologists advise caution as studies primarily involve older participants, and not everyone with misfolded proteins will develop Alzheimer’s.
Another approach measures biological ageing rates, which may not align with chronological age. In 2025, Hariri’s team introduced a tool to assess biological ageing at 45 using a single MRI scan (source). Faster-ageing individuals showed more hippocampal shrinkage and poorer cognitive performance, with increased dementia risk in later years. Hariri emphasizes that while the tool suggests midlife accelerated aging, it is not yet a reliable predictor.
Currently, MRI pace-of-ageing scans cannot reliably predict dementia onset decades later. As Hariri explains, verifying midlife biomarkers requires long-term tracking. Even if reliable predictions become possible, widespread availability faces cost challenges.
There are observable signs today. A recent study found a link between six specific midlife psychological and cognitive symptoms of depression and increased dementia risk in later years (source). Gill Livingston, a professor of psychiatry at University College London, notes that these symptoms may indicate early brain changes, potentially decades before dementia onset.
Livingston also emphasizes the importance of monitoring established indicators like blood pressure and cholesterol for brain health and dementia risk. These are easily trackable and should not be overlooked.
Adopting a healthier lifestyle in midlife can enhance long-term resilience to cognitive decline and potentially delay dementia. The 2024 Lancet Commission on dementia concluded that addressing factors like high blood pressure, obesity, smoking, excessive alcohol use, social isolation, depression, and inactivity could prevent 45% of dementia cases (source).
While awaiting cost-effective biomarker tests and treatments for dementia, middle age offers a critical opportunity to safeguard brain health.
Livingston compares this to pension planning: early investment in brain health, such as lowering blood pressure, yields long-term cognitive benefits. “If you wait, you’re going to have less cognitive reserve [in your later years],” she advises. “Doing it earlier will make a difference.”
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