Age Related Changes in Cerebrovascular Reactivity and Its Relationship to Global Brain Structure

Introduction: There is growing evidence to suggest that vascular and CSF haemodynamic effects are related to structural changes in the ageing brain. We investigated these effects in a sample of healthy participants by measuring changes in cerebrovascular reactivity induced by hypercapnia and comparing these to global and ROI based cerebral volume measures.
Methods: Forty five participants aged 21 to 58 years (23 female) were recruited. Cerebrovascular reactivity was determined from hypercapnia induced BOLD signal change during two 3-minute intervals of breathing 6% CO2, interleaved with three 2-minute intervals of breathing room air. Parametric maps of reactivity were calculated as the ratio of % BOLD signal change to end-tidal CO2 (mmHg). High resolution 3D T1-weighted images were segmented and lateral ventricle volume and white matter hypointensity volume determined.
Results: Significant negative correlations between both grey matter (p = .042) and white matter (p = .021) reactivity and age were found and significant negative correlations between grey matter (p = .013) and white matter (p = .004) reactivity and lateral ventricle volume were also found while correcting for age and total intracranial volume. A significant negative correlation between white matter reactivity and white matter hypointensity volume was found (p = .049) after correcting for age.
Conclusion: These results support the hypothesis that cerebrovascular haemodynamics influence structural brain changes that occur during normal ageing that are independent of the age of the individual.