Are MRI white matter lesions clinically significant in the 'old-old'? Evidence from the Sydney Older Persons Study

The number of individuals aged over 80 years is the fastest increasing group in developed countries. White matter lesions (WML) observed on magnetic resonance imaging (MRI) have uncertain clinical significance, particularly in the old.

To determine the prevalence of periventricular and deep WML in survivors of an original cohort of randomly selected elderly community dwellers, and to examine their associations with clinical markers of vascular and extrapyramidal disorders of ageing, as well as quantitative cognitive measures.

Brain MRI, lifestyle interview, cognitive testing and medical examination were administered to 122 participants from the Sydney Older Persons Study 6-year review (mean age: 85.5 years). Apolipoprotein E (ApoE) genotype was also established. Presence and severity of periventricular and deep WML were ascertained using semi-quantitative rating methods and their relations to the cognitive and clinical variables investigated.

Periventricular WML were present in all participants in similar severity for all three regions sampled. In contrast, a gradient of severity was observed for the deep WML: most severe in the parietal region, followed by the frontal and occipital regions, and least severe in the temporal region. Associations with gender or with the ApoE epsilon4 allele were non-significant. WML were inconsistently associated with age and cognitive functioning or with the clinical markers of dementia. No frontal specificity emerged. Examination of individual lesion types did not change the general pattern of associations. Supporting evidence for a threshold effect was observed on some measures.

WML are extremely common in elderly, non-demented individuals. Unlike in younger individuals, MRI abnormalities may not be evidence of a current pathological process and their importance may change with advancing age.