Meta-Analysis
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Rheumatol. Jul 12, 2016; 6(2): 23-29
Published online Jul 12, 2016. doi: 10.5499/wjr.v6.i2.23
Exercise reduces depressive symptoms in adults with arthritis: Evidential value
George A Kelley, Kristi S Kelley
George A Kelley, Kristi S Kelley, Meta-Analytic Research Group, Department of Biostatistics, School of Public Health, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506-9190, United States
Author contributions: Kelley GA and Kelley KS contributed equally to this work; Kelley GA and Kelley KS designed the research; Kelley GA and Kelley KS performed the research; Kelley GA and Kelley KS analyzed the data; Kelley GA and Kelley KS wrote the paper.
Supported by The National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health (GAK, Principal Investigator), No. RO1AR061346; the National Institute of General Medical Sciences of the National Institutes of Health, No. U54GM104942.
Conflict-of-interest statement: The authors declare that there is no conflict of interest regarding the publication of this paper.
Data sharing statement: Dataset is available from the corresponding author at gkelley@hsc.wvu.edu. Consent was not available because this is an aggregate data meta-analysis in which data were abstracted from previously published studies and in which no individual participant data were used.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: George A Kelley, FACSM, Professor, Director, Meta-Analytic Research Group, Department of Biostatistics, School of Public Health, Robert C. Byrd Health Sciences Center, West Virginia University, PO Box 9190, Morgantown, WV 26506-9190, United States. gkelley@hsc.wvu.edu
Telephone: +1-304-2936279 Fax: +1-304-2935891
Received: July 14, 2015
Peer-review started: July 15, 2015
First decision: August 16, 2015
Revised: January 24, 2016
Accepted: March 7, 2016
Article in press: March 9, 2016
Published online: July 12, 2016
Processing time: 362 Days and 21.7 Hours
Abstract

AIM: To determine whether evidential value exists that exercise reduces depression in adults with arthritis and other rheumatic conditions.

METHODS: Utilizing data derived from a prior meta-analysis of 29 randomized controlled trials comprising 2449 participants (1470 exercise, 979 control) with fibromyalgia, osteoarthritis, rheumatoid arthritis or systemic lupus erythematosus, a new method, P-curve, was utilized to assess for evidentiary worth as well as dismiss the possibility of discriminating reporting of statistically significant results regarding exercise and depression in adults with arthritis and other rheumatic conditions. Using the method of Stouffer, Z-scores were calculated to examine selective-reporting bias. An alpha (P) value < 0.05 was deemed statistically significant. In addition, average power of the tests included in P-curve, adjusted for publication bias, was calculated.

RESULTS: Fifteen of 29 studies (51.7%) with exercise and depression results were statistically significant (P < 0.05) while none of the results were statistically significant with respect to exercise increasing depression in adults with arthritis and other rheumatic conditions. Right-skew to dismiss selective reporting was identified (Z = -5.28, P < 0.0001). In addition, the included studies did not lack evidential value (Z = 2.39, P = 0.99), nor did they lack evidential value and were P-hacked (Z = 5.28, P > 0.99). The relative frequencies of P-values were 66.7% at 0.01, 6.7% each at 0.02 and 0.03, 13.3% at 0.04 and 6.7% at 0.05. The average power of the tests included in P-curve, corrected for publication bias, was 69%. Diagnostic plot results revealed that the observed power estimate was a better fit than the alternatives.

CONCLUSION: Evidential value results provide additional support that exercise reduces depression in adults with arthritis and other rheumatic conditions.

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Core tip: The primary strength of this study was the use of a recent and novel approach to address the potential for selective reporting of statistically significant results, a common problem in the published literature, regarding the effects of exercise on depressive symptoms in adults with arthritis and other rheumatic diseases. The results revealed that selective reporting does not exist, thereby providing further support that exercise improves depressive symptoms in adults with arthritis and other rheumatic diseases.