Validation of the VE/VCO2 Slope as a Marker of Cognitive Performance in Older Adults

Research Objectives: To explore the relationship between older adults’ cardiorespiratory fitness and cognitive health, by evaluating the associations of maximal oxygen consumption (VO2 max) and ventilatory efficiency (VE/VCO2 slope) to global cognitive performance.

Design: Secondary data analysis using linear regression modeling.

Setting: Veterans Affairs Hospital, Palo Alto, CA.

Participants: Subjects included 107 community-dwelling volunteers, ages 54-88 years old (mean 71.7±8.9), recruited for their ability to fully participate in exercise and cognitive testing. Participants were screened for prior psychiatric conditions, major neurocognitive disorders, chronic or acute illnesses (including severe cardiac and respiratory disease).

Interventions: All participants completed a baseline neuropsychological test battery, and underwent maximal graded cardiopulmonary exercise testing (CPET) with breath-by-breath expired gas analysis.

Main Outcome Measures: The primary outcome was performance on a global cognition composite score, comprised from assessments of learning/memory, language fluency, attention/executive function, processing speed, and visuospatial abilities.

Results: At the item level, VE/VCO2 slope was significantly associated with global cognitive performance (β= -0.028, p=.007), whereas VO2 max was not (β=-0.06, p=.59). Controlling for age and education, VE/VCO2 slope accounted for 17% of the variance in outcome scores (F(3,106)=6.88, R2=.167, p<.001). Post-hoc analyses indicated that 27% of participants achieved near-maximal effort during the CPET evaluation (e.g. a Respiratory Exchange Ratio ≥1.1) to accurately reflect maximum aerobic capacity.

Conclusions: Findings indicate VE/VCO2 slope is a valuable marker of cognitive performance in older adults, especially when maximal exertion is not met during CPET testing. This is significant as VO2 max has been considered the criterion standard for measuring general health and fitness, and often used in studies exploring correlates of cognition. Unlike VO2 max, VE/VCO2 slope reflects the degree of ventilatory efficiency in response to exercise, and can be accurately calculated at sub-maximal thresholds. While special considerations should be made when working with older populations, this study validates the VE/VCO2 slope as an alternative exercise measure that should be utilized in future research, especially with those experiencing health or age-related physical limitations.

Author(s) Disclosures: The authors have no disclosures or conflicts of interest to declare.