Higher serum insulin-like growth factor-1 is associated with better cognitive performance in persons with mild...

Serum insulin-like growth factor-1 (IGF-1) is a mitogenic peptide involved in the regulation of cell proliferation, differentiation, and apoptosis in a wide variety of cells and tissues. Recent research suggests higher circulating levels of IGF-1 are associated with better cognitive performance in healthy older adults and in early stages of Alzheimer's disease, although the cognitive profile associated with elevated IGF-1 has not been examined in persons with mild cognitive impairment.

Thirty-one participants (age: 83.71 ± 3.59 years; 58% women) with mild cognitive impairment completed neuropsychological testing and 12-hour fasting blood draw to assess serum IGF-1.

Partial correlations between serum IGF-1 and neuropsychological measures were conducted, adjusting for insulin, body mass index, and age. Higher IGF-1-values were associated with better global cognition (Modified Mini Mental State Exam: r = 0.39, P = 0.04) and verbal list learning (Hopkins Verbal Learning Test learning: r = 0.38, P = 0.05), Hopkins Verbal Learning Test free recall (r = 0.41, P = 0.03), and Hopkins Verbal Learning Test recognition discriminability (r = 0.46, P = 0.01). A similar trend emerged for executive function as tested by the Frontal Assessment Battery (r = 0.33, P = 0.09).

Results suggest higher levels of serum IGF-1 are associated with better cognitive performance in persons with mild cognitive impairment, particularly on tests of learning and memory. These findings suggest IGF-1 may be neuroprotective not only in healthy older adults, but also in adults in the earliest stages of Alzheimer's disease. Further investigation is needed to clarify the nature of this relationship, particularly prospective studies.