It is well known that the average brain size of elderly people is smaller than that of younger ones. Most doctors and scientists have decided that this is a normal part of aging. However, it turns out that this may not be the case.
A new study in the APA journal Neuropsychology used a highly controlled sample from Maastricht University's long-term Aging Study in Holland. These individuals were screened every three years for a wide range of neurological problems, and divided into groups based on level of functioning. Neuropsychological test batteries were used to determine how well participants maintained neural functioning, and MRI scans were used to measure the physical size of seven brain areas important for aging, including hippocampal and parahippocampal areas as well as the frontal and cingulate cortices.
Study participants showed a loss of brain mass in direct relationship to cognitive decline. The researchers conclude that age-related decreases in brain size likely reflect pathological changes in the brain, rather than natural processes of aging.
This is a great example of the need for more cautious and methodical interpretation of clinical research. In attempting to determine what is normal, it is too easy for clinical researchers to miss the mark on what is optimal.
Citation: Burgmans, S., van Boxtel, M.P.J., Vuurman, E.F.M.P., Smeets, F., Gronenschild, E.H.B.M., Uylings, H.B.M., & Jolles, J. (2009). The prevalence of cortical gray matter atrophy may be overestimated in the healthy aging brain. Neuropsychology, 23 (5), 541-550. [PDF]