Practice Effect and Cardiorespiratory Response to Cognitive Test-Retest with Aging

Background: This study aimed to examine the age-related difference in practice effect on cognitive performance and cardiorespiratory frequencies during test and retest with the same materials in different cognitive domains. Methods: Twenty cognitively normal older and younger men and women (65±2 vs 26±1 years old) provided the informed consent (approved by IRB) and participated in cognitive test and retest using Mini-Mental State Examination (MMSE), Digit-Span, Trail Making Test (TMT-B), and California Verbal Learning Test (CVLT-II) with ~3 weeks apart. During the testing, heart rate (HR) and breathing frequency (BF) were continuously monitored from electrocardiogram and plethysmograph. ANOVA was applied to examine the significance of the age and retest factors. Results: All cognitive performances were not affected by the age factor or the retest factor except CVLT-II. Baseline cognitive performances of the older vs younger groups were 27.7±1.1 vs 30.5±0.7 (P=0.034) in CVLT-II total Free-Recall, 29.2±0.4 vs 29.6±0.2 in MMSE, 15.6±1.6 vs 16.7±1.2 in Digit-Span, and 58.8±6.4 vs 48.0±3.6 in TMT-B, respectively. The retest factor only significantly improved total Free-Recall in the younger group (P=0.002). Baseline HR and BF were not different between the two groups, older vs younger: 72±5 vs 80±3 beats/min and 17±1 vs 16±1 breaths/min. Both HR and BF were significantly augmented (P< 0.01) in response to the cognitive test. However, both these responses were significantly attenuated during the retest (the retest factor P< 0.01). Only HR, not BF response was significantly affected by the age factor. Conclusions: There was no practice effect on cognitive performances in MMSE, Digit-Span, and TMT-B in both older and younger subjects. Total Free-Recall was significantly improved in the younger subjects only during the retest. There was a practice effect on the cardiorespiratory responses to cognitive challenge, which were significantly reduced during the cognitive retest. Aging significantly diminished HR response during cognitive challenge.