Sex Differences and Age-Related Decline in Absolute Cerebral Metabolic Rate of Oxygen (CMRO2) Consumption

Abstract

<p><b>Motivation:</b> Resting CMRO₂ is a marker of brain health that may inform typical and pathological brain aging. However, there is conflicting literature describing how CMRO₂ changes across the lifespan, which may be influenced by extraneous variables such as sex and end-tidal partial pressure of carbon dioxide (P_ETCO₂).</p> <p><b>Goal(s):</b> This study aimed to evaluate CMRO₂ changes across the lifespan, after considering these possible confounding variables.</p> <p><b>Approach:</b> Dual-calibrated BOLD fMRI quantified grey matter absolute CMRO₂ in 83 participants.</p> <p><b>Results:</b> Sex and age significantly predicted CMRO₂. Females had higher CMRO₂ than males, and CMRO₂ decreased with increasing age for females.</p> <p><b>Impact:</b> Grey matter CMRO₂ decreases in normal healthy aging. Considering both sexes, the CMRO₂ decline rate was -0.88 per year, after accounting for P_ETCO₂ and sex. When males and females were analysed separately, females only showed a significant decline with age.</p>