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As the years go by, recalling recent events or past experiences often becomes more difficult. Although this phenomenon is well known, its causes have been less clear. A recent international study provides new evidence to better understand how and why episodic memory (the ability to recall lived experiences) changes with age, showing that the process is more complex than previously thought.
The research combined data from more than 3,700 cognitively healthy adults, followed over several years, and integrated over 10,000 MRI scans and more than 13,000 memory assessments from 13 different longitudinal studies. Academic institutions and research centers from Europe and the United States participated, including universities and specialized centers in aging and neuroscience from countries such as Norway, the United Kingdom, Germany, Spain, Italy, Denmark, Sweden, Switzerland, and the United States. The work was published in Nature Communications.
One of the main findings is that the relationship between brain shrinkage and memory loss is neither simple nor linear. As people age, especially after the age of 60, structural brain changes become more relevant to memory performance. Moreover, those who experience faster-than-average brain volume loss tend to undergo disproportionately greater memory decline. In other words, once certain structural changes intensify, their cognitive impact appears to accelerate.
Although the hippocampus—a key region for memory and learning—showed the strongest association between volume loss and poorer memory performance, the phenomenon is not limited to that area. The analysis revealed significant relationships between structural changes and memory across multiple cortical and subcortical regions. Rather than the deterioration of a single isolated structure, the results point to a distributed vulnerability of the brain, manifesting as a gradient: stronger effects in the hippocampus and smaller but consistent effects across wide areas of the brain.
The study also examined the role of genetic factors associated with Alzheimer’s disease risk, such as the APOE ε4 gene. While carriers of this gene showed faster brain volume loss and accelerated memory decline, the overall trajectory was similar to that of the rest of the participants. This suggests that the observed changes are not driven exclusively by a specific genetic risk, but are part of broader processes of brain aging.
Taken together, the findings reinforce the idea that cognitive decline in old age is not simply an inevitable consequence of time passing, nor the result of a single cause. Rather, it reflects the interaction between individual predispositions and biological processes that accumulate over decades, leading to greater structural vulnerability of the brain.
From a clinical and preventive perspective, these results have important implications. If memory loss is associated with distributed and progressive changes, strategies to prevent or delay cognitive decline will likely need to consider multiple brain regions and begin as early as possible. At the same time, the fact that the underlying mechanisms are shared suggests that interventions could be useful both for people with and without known genetic risk factors.
As understanding of these processes advances, the possibility opens up of identifying at-risk individuals earlier and developing more precise, personalized interventions. Understanding how the brain ages as a whole emerges as a key piece in promoting better cognitive health throughout life.
