Using serial magnetic resonance imaging to identify age-related brain structure changes

1. In this prospective cohort study, it was found that the lateral ventricles, front and temporal lobes, and anterior and inferior white matter regions exhibited the greatest age dependency on volume change, though all structures examined appeared to accelerate in volume loss with age, 

Evidence Rating: 1 (Excellent)

The literature indicates that many neurodegenerative diseases begin to take place decades prior to symptom onset. Gathering a better understanding of the longitudinal patterns of change in different regions of the brain could provide insights into these early processes. This is the first large-scale longitudinal study that harnesses magnetic resonance imaging (MRI) of the brain in individuals without dementia as a means to quantify aging-related changes in brain volume. A total of 653 participants (mean [SD] age at baseline, 55.1 [9.3] years; median age, 55 years [IQR, 47-62 years]; 447 men [69%]) from a Japanese comprehensive screening program participated in more than 10-year serial visits. Each brain structure showed individual levels of age-dependent volume change, and an annual decrease of 0.4% of whole-brain volume was observed. In particular, a marked volume decrease in the parenchyma and an increase in CSF space (ventricles and sulci) were observed (ventricle regression coefficient, 0.042 [95% CI, 0.037-0.047]; P < .001; sulcus regression coefficient, 0.021 [95% CI, 0.018-0.023]; P < .001). Specifically, the lateral ventricle exhibited the largest changes in growth from year to year. The frontal and temporal lobes showed a larger age dependency than the parietal and occipital lobes, and white matter regions in the anterior and inferior portions of the brain showed greater age dependency than the posterior white matter. Cerebellar volume loss accelerated linearly with age. Cerebral cortex volume loss was gradual, at 0.4% across all decades of life. The hippocampus and temporal lobe both demonstrated rapidly accelerating volume decreases with increasing age, but the hippocampus was more preserved in the earlier stages of life. While this study is the largest of its kind to date and uses longitudinal imaging data to inform its results, there is no way to quantify whether participants were already in the pre-clinical Alzheimer’s disease stages when entering the study. The homogeneity of this population also prevents generalizability. However, overall, characterizing the normal distributions of brain volume and atrophy rates in a cognitively healthy population could potentially allow the medical community to risk-stratify high-risk subgroups and facilitate stratification of high-risk subgroups.

Click to read the study in JAMA Network Open

Image: PD

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