Do your brains really shrink as you get older?
Your brain does indeed shrink measurably as you get older, but this far from always leads to noticeable cognitive decline. Addressing vascular risk factors such as high blood pressure and staying active are the most concrete tools for slowing the pace of that decline.
Yes, the brain really does shrink over the years. In healthy older adults, the outer layer of the brain (the cerebral cortex) declines by about three-quarters of a percent per year. White brain tissue continues to grow slightly until your forties, but then declines at a similar rate. At the same time, the space filled with cerebrospinal fluid increases: on average, roughly 30 ml is added every ten years. The cavities deep in the brain do not grow substantially until after the age of sixty.
Beyond volume loss, the quality of brain tissue also changes. The insulating layer around nerve fibres wears down, iron content decreases, and the amount of free water increases. This affects the motor and executive brain networks in particular. At the cellular level, nerve cells become smaller and their branches degenerate. These are processes that are normal in themselves during ageing, but they can also be the precursor to dementia.
The good news: brain shrinkage does not necessarily have a direct impact on how you think. In healthy older adults, IQ remained stable over four years despite measurable shrinkage. Yet in a larger group, shrinkage of grey brain tissue in the temporal lobe turned out to be the strongest predictor of cognitive decline. Volume loss and cognitive loss therefore do not always go hand in hand.
Some factors accelerate the process. High blood pressure and atherosclerosis affect not only brain volume but also the robustness of brain networks. This loss of network integrity is associated with poorer cognition, independently of volume loss itself. Keeping vascular risk factors under control protects not only the heart but also the brain.
There are also indications that brain volume loss can be partially counteracted. A systematic review of eight small randomised studies shows that regular dancing can increase hippocampal volume. The evidence base for this type of intervention is still limited, but it suggests that staying active genuinely makes a difference.
Based on multiple large-scale MRI studies (involving up to nearly one thousand participants) and a four-year longitudinal study in healthy older adults. The associations are robust and consistent. Causal relationships have not been proven: the data are observational. The intervention study (dancing) is based on only eight small RCTs.