Karrer Teresa M, Josef Anika K, Mata Rui, Morris Evan D, Samanez-Larkin Gregory R
Department of Psychology, Yale University, New Haven, CT, USA.
Center for Adaptive Rationality, Max Planck Institute for Human Development, Berlin, Germany.
Neurobiol Aging. 2017 Sep;57:36-46. doi: 10.1016/j.neurobiolaging.2017.05.006. Epub 2017 May 12.
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.
许多认知衰老理论都基于多巴胺（DA）随年龄下降的证据。在此，我们对正电子发射断层扫描和单光子发射计算机断层扫描的横断面研究进行了系统的荟萃分析，以探讨年龄对健康成年人（N = 95项研究，包括2611名参与者）不同DA靶点（受体、转运体或相关酶）的平均影响。结果显示，年龄对DA转运体和受体有显著的中度至较大的负面影响。年龄对D1样受体的影响比对D2样受体的影响显著更大。相比之下，年龄对DA合成能力没有显著影响。整个DA系统中，每十年的平均年龄降幅为3.7%-14.0%。一项荟萃回归发现，只有DA靶点是年龄效应的显著调节因素。本研究精确量化了先前关于DA功能随年龄降低的说法。它还确定了突触前机制（合成能力保留和DA转运体减少），这些机制可能部分解释了以前无法解释的现象，即老年人似乎能有效利用多巴胺能资源。本文还提供了对未来研究的建议，包括所需的最小样本量。
