Cheng Yang, MM*; Lei Li, MD*; Xinyu Hu, PhD*; Qiang Luo, MM; Weihong Kuang, MD; Su Lui, MD, PhD; Xiaoqi Huang, MD, PhD; Jing Dai, MD; Manxi He, MD; Graham J. Kemp, DSc; John A Sweeney, PhD; Qiyong Gong, MD, PhD
Background: An increasing number of psychoradiology studies that use tract-based spatial statistics (TBSS) of diffusion tensor imaging have reported abnormalities of white matter in patients with bipolar disorder; however, robust conclusions have proven elusive, especially considering some important clinical and demographic factors. In the present study, we performed a quantitative meta-analysis of TBSS studies to elucidate the most consistent white-matter abnormalities in patients with bipolar disorder.
Methods: We conducted a systematic search up to May 2017 for all TBSS studies comparing fractional anisotropy (FA) between patients with bipolar disorder and healthy controls. We performed anisotropic effect size–signed differential mapping meta-analysis.
Results: We identified a total of 22 data sets including 556 patients with bipolar disorder and 623 healthy controls. We found significant FA reductions in the genu and body of the corpus callosum in patients with bipolar disorder relative to healthy controls. No regions of increased FA were reported. In subgroup analyses, the FA reduction in the genu of the corpus callosum retained significance in patients with bipolar disorder type I, and the FA reduction in the body of the corpus callosum retained significance in euthymic patients with bipolar disorder. Meta-regression analysis revealed that the percentage of female patients was negatively correlated with reduced FA in the body of the corpus callosum.
Limitations: Data acquisition, patient characteristics and clinical variables in the included studies were heterogeneous. The small number of diffusion tensor imaging studies using TBSS in patients with bipolar disorder type II, as well as the lack of other clinical information, hindered the application of subgroup meta-analyses.
Conclusion: Our study consistently identified decreased FA in the genu and body of the corpus callosum, suggesting that interhemispheric communication may be the connectivity most affected in patients with bipolar disorder.
*These authors contributed equally to the work.
Submitted Nov. 2, 2017; Revised Feb. 10, 2018; Accepted Feb. 26, 2018; Published online Aug. 29, 2018
Acknowledgments: This study was supported by the National Natural Science Foundation of China (grant nos. 81621003, 81220108013, 81761128023, 81227002 and 81030027), the National Key Technologies R&D Program (program no. 2012BAI01B03) and the Program for Changjiang Scholars and Innovative Research Team (PCSIRT, grant no. IRT16R52) at the University of China. Q. Gong acknowledges support from his Changjiang Scholar Professorship Award of China (award no. T2014190) and American CMB Distinguished Professorship Award (award no. F510000/G16916411), administered by the Institute of International Education, in the United States.
Affiliations: From the Huaxi MR Research Center (HMRRC), Department of Radiology, West China Hospital of Sichuan University, China (Yang, Li, Hu, Luo, Lui, Huang, Sweeney, Gong); the Department of Psychiatry, West China Hospital of Sichuan University, China (Kuang); the Department of Psychoradiology, Chengdu Mental Health Center, China (Kuang, Dai, He); the Liverpool Magnetic Resonance Imaging Centre (LiMRIC) and Institute of Ageing and Chronic Disease, University of Liverpool, United Kingdom (Kemp); the Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, Ohio, United States (Sweeney); and the Department of Psychology, School of Public Administration, Sichuan University, China (Gong).
Competing interests: None declared.
Contributors: C. Yang, L. Li, X. Hu and Q. Gong designed the study. C. Yang and L. Li acquired and analyzed the data, which X. Hu, Q. Luo, W. Kuang, S. Lui, X. Huang, J. Dai, M. He, G.J. Kemp and J.A. Sweeney also analyzed. C. Yang, L. Li, X. Hu, Q. Luo, W. Kuang and J. Dai wrote the article, which all authors reviewed. All authors approved the final version to be published and can certify that no other individuals not listed as authors have made substantial contributions to the paper.
Correspondence to: Q. Gong, Huaxi MR Research Center and Department of Radiology, West China Hospital of Sichuan University, Chengdu, 610041, China; firstname.lastname@example.org; or M. He, Department of Psychoradiology, Chengdu Mental Health Center, Chengdu, 610031, China; email@example.com