Population-based structural imaging of grey- and white-matter integrity in aging

Effects of aging on brain integrity have been extensively studied for many years. One important drawback of previous studies is that most studies included individuals spanning all of adulthood with a bias towards younger individuals, which has led to limited knowledge about age-related effects in late adulthood. Another important issue is the health status of the individuals enrolled in brain imaging studies. Because the aim is often to describe successful aging, massive exclusion of older participants with age-related diseases is common. The findings of such studies do not reflect loss of brain integrity in the general aging population, which is more likely characterized by chronic multimorbidity. Conversely, since most studies have been cross-sectional, there is a risk that people with preclinical dementia were included, which may affect the results. A way to overcome these issues is to investigate brain integrity via longitudinal population-based studies. A total of 555 participants in the SNAC-K study underwent structural MRI at baseline and three and/or six years later. Our most relevant findings in 2011 and 2012 were:

a. Individual differences in white matter microstructure as measured using DTI are structured according to tracts, and aging is not a process with homogenous effects on white matter microstructure across the brain1.

b. Ongoing work using T1-weighted MR images shows that the hippocampus undergoes the strongest age-related volume reduction, even after exclusion of people with preclinical dementia. This result contrasts with the results of previous studies, which show preservation of the structure when comparing younger to healthy young-older adults.

Forthcoming studies concern i) the effects of health status and environmental factors, such as physical activity and genetics on brain integrity and cognition and ii) assessment of longitudinal effects on grey and white matter macro- and micro-structural changes.

  1. Lövdén M, Laukka EJ, Rieckmann A, Kalpouzos G, Li T-Q, Jonsson T, et al. The dimensionality of between-person differences in white matter microstructure in old age. Hum Brain Mapp 2013; 34(6):1386-1398