Effects of Working Memory Load on Performance and Cardiovascular Activity in Younger and Older Workers

Abstract

Working memory (WM) declines with ageing, and this may cause problems in older workers who have to do complex work requiring WM. We tested the assumption that an increase in WM load negatively affects performance and results in impaired cardiovascular adaptation to changing task demands in older workers relative to younger ones. Thirty-three younger (29 ± 3years) and 32 older (55 ± 3years) workers had to perform a visual 0-back (low WM load) and 2-back (high WM load) task. Heart rate (HR), heart rate variability (HRV), beat-to-beat blood pressure (BP) and baroreflex were registered. In the high WM load condition, older adults responded more slowly and less accurately than younger adults, while no age effects in the low WM load condition were found. Older workers showed a higher systolic blood pressure (SBP) reactivity to high WM load as well as a diminished post-task recovery of SBP and HRV than younger workers. Factor analysis demonstrated a close relationship between HR, baroreflex and HRV and their modulation by a common factor ("vagal tone") in the younger group. By contrast, HR was more related to the "sympathetic" factor in the older group. The data suggest that older workers as compared with younger ones are impaired in tasks requiring WM, which is accompanied by enhanced cardiovascular "costs" in terms of increased SBP and reduced vagal control over HR.