Serum neurotrophins--a study on the time course and influencing factors in a large old age sample.

The neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are important mediators of brain and neuronal development, the maintenance of homeostatic conditions in the adult nervous system, and the complex interplay of central and peripheral physiological and pathophysiological factors. To date there are few studies examining blood concentrations of neurotrophic factors in large samples of healthy and diseased individuals and no published study specifically addresses peripheral BDNF and NGF levels in late life. Using improved highly sensitive and specific fluorometric two-site enzyme-linked immunosorbent assays we examined BDNF (n=465) and NGF (n=175) serum levels in a large cohort of elderly individuals (age range: 70-103 years). Neither BDNF nor NGF serum levels proved to be normally distributed, indicating that previously published studies with small sample sizes using parametric testing may be misleading. A significant correlation was found between BDNF and platelet count (r=0.344, p<0.01), age and BDNF protein (r=-0.101, p=0.029) and BDNF and NGF serum levels (r=0.152, p=0.04). No other major influencing factors were found including gender, depression, and dementia.