Cognitive complaints associated with spatial coefficient of cerebral blood flow in community-dwelling older people in the PREvention of Dementia by Intensive VAscular care (PREDIVA) study

Background: Low cerebral perfusion is cross-sectionally associated with dementia and predicts accelerated dementia progression. Hypothetically, impaired cerebral autoregulation, associated with aging and hypertension, and consequent cerebral hypoperfusion may contribute to the development of old-age cognitive decline. We investigated the cross-sectional and longitudinal relation between cognition and cerebral perfusion in older people without dementia using arterial spin labeling (ASL).
Methods: We included 186 community-dwelling individuals with hypertension (77 ±3 years, 53% female), 125 (67%) with 3-year follow-up neuroimaging (Figure 1). Cognitive measures included the mini-mental state examination (MMSE), visual association test (VAT) and subjective memory complaints (SMC) assessed using one question. Perfusion measures included grey matter (GM) cerebral blood flow (CBF, ml/100g/min), white matter (WM) CBF and spatial coefficient of variation (CoV; SD CBF/mean CBF, a potential proxy of vascular insufficiency). Cross-sectional analyses combined baseline and follow-up data using mixed models. Longitudinal analyses comprised linear regression of follow-up values adjusted for baseline. We additionally adjusted for age, sex, antihypertensives, WM hyperintensity volume and brain parenchymal fraction.
Results: Participants with memory complaints had a significantly higher CoV (Table 1). Furthermore, participants with better VAT scores had lower CoV, although this was attenuated after adjustment. Cerebral perfusion did not predict change in cognition (Table 2) but increasing CoV was associated with declining MMSE and, to a lesser extent, VAT scores. There were no significant relations between CBF and cognition.
Discussion: Our results suggest that higher CoV is associated with worse cognitive function and CoV changes concordantly with cognitive function. Spatial CoV may be a more sensitive cerebral hemodynamic parameter related to cerebral function compared to CBF. None of the cerebral perfusion parameters predicted future cognitive decline, suggesting that low perfusion does not precede cognitive decline in non-demented older people or that the perfusion measures employed were insufficiently sensitive.