To understand brain changes throughout life, neuroscientists have primarily examined the early and late stages: the rapid formation and elimination of neural connections in childhood and adolescence, followed by degeneration in old age. “We often overlook midlife,” says Sebastian Dohm-Hansen, a bioinformatician from University College Cork, Ireland.
Historically, this oversight makes sense as significant brain structure and function changes are easier to identify using neuroimaging techniques. Many cognitive declines, especially those associated with dementia, “are most noticeable after 60,” according to Dohm-Hansen.
Recently, however, researchers have started to scrutinize the midlife brain more closely, revealing subtle yet vital changes between the ages of 40 and 65. This phase is increasingly recognized as crucial for identifying potential cognitive issues that may not manifest until later.
“Consider midlife as the peak of an inverted U-curve,” explains Ahmad Hariri, a professor of neuroscience at Duke University. Individuals build and enhance their brains during their early decades and likely face gradual declines afterward. “Focusing on midlife can help extend the flat portion at the top of the curve and slow cognitive decline.”
Research indicates that the most notable midlife changes include altered connectivity that affects how neurons transmit signals over long distances and how the brain organizes its processing. This connectivity reaches its zenith in middle age before declining sharply thereafter as demonstrated in a recent study by Dohm-Hansen and colleagues.
The extent of decline is correlated with individuals’ cognitive abilities, particularly their capacity to remember everyday occurrences. “Midlife represents a tipping point,” says Dohm-Hansen, offering insights into potential future cognitive challenges. Tracking these changes can be complicated; connectivity among certain brain networks may increase to offset losses in others, varying significantly among individuals.
Fortunately, promising new methods for detecting early cognitive decline and dementia are emerging. Notably, blood-based biomarker tests offer the ability to identify misfolded amyloid beta and tau proteins—key contributors to Alzheimer’s disease—long before symptoms arise according to recent findings.
These tests might soon become standard practice in clinical settings, potentially enabling routine screenings. They are, in fact, already available to consumers, though neurologists encourage caution, as most studies were conducted in older populations. Additionally, not everyone with these misfolded proteins will develop Alzheimer’s disease.
Another emerging approach involves new techniques for measuring biological aging rates, which do not always align with chronological aging. In 2025, Hariri and his team developed a tool that estimates an individual’s biological aging rate at age 45 from a single brain MRI scan. The analysis revealed that older individuals exhibiting accelerated aging had greater hippocampal atrophy, leading to poorer performance on cognitive assessments and higher rates of cognitive impairment and dementia risk in subsequent years. “Our tool effectively measures accelerated aging in midlife and may also predict later dementia in individuals aged 60 to 80,” states Hariri. However, these associations were drawn from short-term studies, making them unreliable as predictive tools for the time being.
Like blood biomarker tests, MRI aging pace scans currently cannot definitively predict whether a 45-year-old will develop dementia by age 75. “Longitudinal studies are key to understanding how midlife biomarkers predict later health outcomes,” emphasizes Hariri. Even if reliable predictive metrics become available, their costs may hinder widespread access.
Nevertheless, there are observable signs to watch for today. A recent study highlighted six specific psychological and cognitive symptoms of midlife depression—such as diminished self-confidence and persistent anxiety—that increase the risk of dementia later in life. “These could serve as early indicators of brain changes occurring up to 20 years before dementia onset,” explains Gil Livingston, professor of psychiatry at University College London, and co-author of the study. “Our mental and emotional states may prove to be as valuable as MRIs and biomarkers in predicting cognitive health, but further research is needed.”
Livingston also notes the importance of established early indicators of brain health and dementia risk—such as blood pressure and cholesterol levels—which are easily assessable. “These shouldn’t be overlooked,” she advises.
In fact, growing evidence suggests that adopting a healthier lifestyle during midlife can bolster resilience against cognitive decline and even “prevent” dementia altogether. This implies that symptoms may be delayed such that they do not manifest during one’s lifetime. The latest Lancet Commission on Dementia, published in 2024, concluded that 45% of dementia cases could be averted by addressing essential lifestyle factors like high blood pressure, obesity, smoking, excessive alcohol use, social isolation, depression, and inactivity. Taking action during midlife has a particularly profound impact on reducing dementia risk later in life.
Thus, while we await dependable and cost-effective blood biomarker tests and effective dementia treatments, midlife emerges as a critical period for safeguarding brain health.
Livingston likens this to pension planning; the earlier you invest in brain health—such as via blood pressure management—the greater your long-term cognitive resilience will be. “Delaying this effort diminishes your cognitive reserve,” she warns. “Taking actions early leads to significant improvements.”
Topics:
Source: www.newscientist.com