Our brains undergo constant change throughout our lives. As we age, brain regions and blood vessels change in size and vascularity, respectively. These changes are pronounced in individuals experiencing cognitive decline such as those with Alzheimer’s disease. However, not everyone ages the same way. Some people maintain their cognitive abilities well into their later years, while others experience decline earlier. 

Understanding these patterns and the timing of changes in the brain determines whether someone is ageing normally or developing age-related health issues. This would allow the development of early and effective interventions, believes Vivek Tiwari, Assistant Professor, Indian Institute of Science Education and Research (IISER), Berhampur, and Neha Yadav, PhD student, co-authors on the recent study on brain ageing published in Translational Psychiatry.

White matter hyperintensity (WMH), is a brain lesion resulting from cerebral small vessel diseases. It is a definitive marker of ageing. Tiwari’s research team found it intriguing that even cognitively normal individuals experience displayed higher levels of WMH in the brain. 

This raised an important question to the authors: Why do some people show signs of brain damage but remain cognitively healthy, while others with similar damage experience cognitive decline? And can WMH be one of the defining features to be used to analyse brain age in individuals? 

Tiwari believes quantitative neuroimaging together with estimation of small vessel disease load offers new insights into the biological underpinning of ageing and ageing associated cognitive disorders. 

The researchers used MRI scans to measure brain features like neuroanatomical volume, cortical thickness, and WMH volume in individuals from the National Alzheimer’s Coordinating Center
(NACC) cohort.

They found that WMH increased rapidly with age in cognitively normal individuals and was consistently higher in those with cognitive impairment, regardless of age. This led them to explore how WMH affects brain health. Their study showed that just three brain measures — total brain volume (gray matter + white matter), cerebrospinal fluid (CSF), and WMH volume — were enough to distinguish between brain health in individuals.

To further investigate WMH’s impact on brain health, Tiwari and his team created a Brain Age estimation model. This model used 178 brain features. Using these neuroanatomic features from healthy individuals without WMH, the researchers created a ​“Brain Age Index,” which estimates an individual’s brain age, indicative of brain health, relative to their chronological age.

From the cohort analysed in the study, the researchers found that individuals with higher WMH levels often had an elevated brain age, indicating an accelerated brain decline. 

Arpan Banerjee, Professor at the National Brain Research Centre, Manesar, an expert in neurocomputation, commends the authors for including a larger sample cohort with equal gender representation. He also emphasises that the model could be further improved by incorporating additional features based on functional analysis. 

Brain Age Index is not just a tool for cognitively impaired individuals. It offers a new tool for assessing brain health. It could help doctors identify individuals at risk for cognitive decline based on their brain age compared to their chronological age. As researchers continue to explore how brain structure affects cognitive function, findings like these become essential for shaping future strategies. 

The study’s findings could have important implications for the early detection of cognitive impairments and Alzheimer’s Disease.

This research highlights the complexity of brain health and its impact on cognition. As the population ages, these insights will be crucial for addressing the challenges of cognitive decline and improving the quality of life for older adults. Integrating advanced neuroimaging findings with clinical practice will be key in our quest to improve brain health across the lifespan.