Lifespan mental activity predicts diminished rate of hippocampal atrophy

Abstract

Epidemiological studies suggest that complex mental activity may reduce the risk for dementia, however an underlying mechanism remains unclear. Our objective was to determine whether lifespan complex mental activities were linked to altered rates of hippocampal atrophy. Complex mental activity was estimated using the Lifetime of Experiences Questionnaire (LEQ) in healthy elderly controls from the Sydney Stroke Study, a 5-year longitudinal study (N=70). Manual tracing of hippocampal volume and semi-automated quantitation of whole brain volume (WBV) and white matter hyperintensities (WMHs) was completed on MRI scans at baseline and 3-year follow up. Individuals were median-split into high and low LEQ groups, whereby high LEQ was indicative of greater mental activities. Partial correlation analysis found those with higher LEQ scores experienced less hippocampal atrophy over the follow-up period (r=0.37, p=0.036). High LEQ individuals had less than half the hippocampal volume decline of low LEQ individuals in a multivariate analysis (F=5.97, p=0.02). No parallel changes were found in measures of WBV and WMHs. High level of complex mental activity across the lifespan was related to a reduced rate of hippocampal atrophy. This finding could not be explained by general differences in intracranial volume, larger hippocampi at baseline, presence of hypertensive disease or low mood. Our results suggest that neuroprotection in medial temporal lobe may be one mechanism underlying the link between mental activity and lower rates of dementia observed in population-based studies.