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Low Levels of Insulin-like Growth Factor I Linked to Cognitive Decline: Presented at IADRD

By Peggy Peck
Special to DG News

STOCKHOLM, SWEDEN -- July 29, 2002 -- Results of a prospective study of 1,318 elderly residents of the Netherlands suggests that low levels of insulin-like growth factor (IGF-I) impair information-processing speed.

Miranda Dik, PhD, of the Institute for Research in Extramural Medicine, Amsterdam, the Netherlands, said information-processing speed is a major component of cognitive decline. Thus, increasing the level of IGF-I through improved nutrition "may prevent cognitive decline."

The research was presented here July 25 at the 8^th International Conference on Alzheimer's Disease and Related Disorders (IADRD).

This study indicates that IGF-I levels below a certain threshold (<9.39 nmol/L) affect both the level and rate of decline of information-processing speed.

Information-processing is assumed to be the basic component of all other cognitive functions. This suggests that increasing the level of IGF-I by improving nutritional status in elderly with low IGF-I levels may prevent cognitive decline.

The Longitudinal Aging Study Amsterdam (LASA) enrolled 1,318 subjects aged 65-88. All subjects underwent medical examination as well as cognitive testing consisting of the Mini-Mental State Examination (MMSE), an abbreviated Auditory Verbal Learning Test (memory), a substitution Coding Task (information processing speed), and Raven's Colored Progressive Matrices (fluid intelligence). Cognitive tests were repeated after three years follow-up.

Cross-sectionally, IGF-I was inversely related to all cognitive measures, but not significantly after adjustment for age, sex, education, weight, albumin, number of chronic diseases, functional limitations, depression, and physical activity.

Analysis in quintiles of IGF-I revealed a threshold effect of low IGF-I on information-processing speed, with lower speed in subjects in the lowest quintile of IGF-I (<9.39 nmol/L) versus those in the highest four quintiles (adjusted standardized ß =-0.05; p=0.04).

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