The relation between insulin-like growth factor I levels and cognition in healthy elderly: a meta-analysis.
OBJECTIVE
Insulin-like growth factor I (IGF-I) levels and cognitive functioning decrease with aging. Several studies report positive correlations between IGF-I levels and cognitive functioning in healthy elderly. However, because of controversial data no definitive conclusions can be drawn concerning the relation between IGF-I and cognition. Therefore, we carried out a meta-analysis on studies that report on the relation between IGF-I and cognition in healthy elderly.


METHODS
We searched the electronic databases for articles about IGF-I and cognition. Studies from 1985 to January 2005 are included. Two reviewers independently extracted data on study design and cognitive outcomes. Thirteen studies on IGF-I and cognition in elderly, with a total number of 1981 subjects, met the inclusion criteria. On the data from these studies meta-analyses were carried out by means of the program Comprehensive Meta-analysis using a random effects model.


RESULTS
Pooled effects show that IGF-I levels in healthy elderly have a positive correlation with cognitive functioning, which appeared to be mainly measured with the mini mental state examination (MMSE). The effect size is 0.6, which indicates the presence of a large positive relationship between IGF and cognition in healthy elderly.


CONCLUSIONS
These meta-analyses showed an overall relationship between IGF-I levels and cognitive functioning in healthy elderly. Further studies should be performed to clarify the role of IGF-I substitution in preserving cognitive functions with aging.
Arwert
L I
LI
Department of Endocrinology, VU University Medical Center, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands. l.arwert@vumc.nl
Deijen
J B
JB
Drent
M L
ML
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D001288:Attention; D003071:Cognition; D003072:Cognition Disorders; D005260:Female; D013006:Growth Hormone; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008297:Male; D008568:Memory; D008569:Memory Disorders; D008609:Mental Status Schedule; D008875:Middle Aged; D009483:Neuropsychological Tests; D011795:Surveys and Questionnaires
D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone