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Neurobiol Aging. 2017 Sep;57:36-46. doi: 10.1016/j.neurobiolaging.2017.05.006. Epub 2017 May 12.

Reduced dopamine receptors and transporters but not synthesis capacity in normal aging adults: a meta-analysis.

Author information

1
Department of Psychology, Yale University, New Haven, CT, USA. Electronic address: tkarrer@ukaachen.de.
2
Center for Adaptive Rationality, Max Planck Institute for Human Development, Berlin, Germany.
3
Center for Cognitive and Decision Sciences, University of Basel, Basel, Switzerland.
4
Yale PET Center, Yale University, New Haven, CT, USA; Department of Biomedical Engineering, Yale University, New Haven, CT, USA; Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA; Department of Psychiatry, Yale University, New Haven, CT, USA.
5
Department of Psychology, Yale University, New Haven, CT, USA; Center for Cognitive Neuroscience, Duke University, Durham, NC, USA. Electronic address: g.samanezlarkin@duke.edu.

Abstract

Many theories of cognitive aging are based on evidence that dopamine (DA) declines with age. Here, we performed a systematic meta-analysis of cross-sectional positron emission tomography and single-photon emission-computed tomography studies on the average effects of age on distinct DA targets (receptors, transporters, or relevant enzymes) in healthy adults (N = 95 studies including 2611 participants). Results revealed significant moderate to large, negative effects of age on DA transporters and receptors. Age had a significantly larger effect on D1- than D2-like receptors. In contrast, there was no significant effect of age on DA synthesis capacity. The average age reductions across the DA system were 3.7%-14.0% per decade. A meta-regression found only DA target as a significant moderator of the age effect. This study precisely quantifies prior claims of reduced DA functionality with age. It also identifies presynaptic mechanisms (spared synthesis capacity and reduced DA transporters) that may partially account for previously unexplained phenomena whereby older adults appear to use dopaminergic resources effectively. Recommendations for future studies including minimum required samples sizes are provided.

KEYWORDS:

Dopamine; Healthy aging; Meta-analysis; Receptors; Synthesis capacity; Transporters

[Indexed for MEDLINE]
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