Brain age is a measure of volume and structure of the brain derived from machine learning techniques applied to databases of imaging of brain tissue at various ages and in healthier individuals versus patients with neurodegenerative conditions. Here, researchers demonstrate that, as one might expect, brain age is higher in patients with mild cognitive impairment and Alzheimer’s disease. Surprisingly, however, there is a greater acceleration of brain aging in the earlier mild cognitive impairment stage than in the later Alzheimer’s disease stage. This is another data point indicating the need for early intervention in the path towards Alzheimer’s disease.
Brain age is a machine learning-derived estimate that captures lower brain volume. Previous studies have found that brain age is significantly higher in mild cognitive impairment and Alzheimer’s disease (AD) compared to healthy controls. We utilized data from an archival dataset, mainly Alzheimer’s disease Neuroimaging Initiative (ADNI). We included control participants (healthy controls or HC), individuals with mild cognitive impairment (MCI), and individuals with Alzheimer’s disease (AD). We conducted longitudinal modeling of age and brain age by group using time from baseline in one model and chronological age in another model.
We predicted brain age with a mean absolute error (MAE) of less than 5 years. Brain age was associated with age across the study and individuals with MCI and AD had greater brain age on average. We found that the MCI group had significantly higher rates of change in brain age over time compared to the HC group regardless of individual chronologic age, while the AD group did not differ in rate of brain age change. We essentially found that while the MCI group was actively experiencing faster rates of brain aging, the AD group may have already experienced this acceleration (as they show higher brain age). AD may represent a homeostatic endpoint after significant neurodegeneration. Future work may focus on individuals with MCI as one potential therapeutic option is to alter rates of brain aging, which ultimately may slow cognitive decline in the long-term.
