The Moderating Role of Insulin-Like Growth Factor 1 in the Relationship Between Cognitive and Aerobic Endurance Change.

BACKGROUND: Improvements in cognition often accompany fitness improvements in older adults, and research suggests insulin-like growth factor 1 (IGF-1) may influence this association. No prior work has examined this in mild cognitive impairment (MCI). We predicted that IGF-1 would moderate the relationship between cognition and aerobic endurance improvement, such that greater baseline IGF-1 would accompany a stronger relationship between cognition and aerobic endurance change.

METHOD: Twenty-seven individuals with MCI completed assessments of aerobic endurance (2-minute step test [2MST]) and global cognition (Modified Mini-Mental State [3MS]) before and after a 6-month period of twice-weekly exercise. Serum IGF-1 levels were assessed at baseline via fasted blood draw. The Johnson-Neyman technique determined whether baseline IGF-1 levels moderated the relationship between changes in aerobic endurance (Δ2MST) and cognition (Δ3MS).

RESULTS: A significant interaction was found; however, Δ2MST was inversely associated with Δ3MS in individuals with above-average serum IGF-1 levels; this relationship was strengthened as IGF-1 increased and was not seen when IGF-1 was below average.

CONCLUSION: The relationship between cognitive and aerobic endurance change varies as a function of IGF-1 in persons with MCI. Additional work is needed to clarify the mechanisms of these findings.