TY - JOUR T1 - Metaanalyses, Network Metaanalyses, and Systematic Reviews: The Perpetual Motion Machine All Over Again JF - The Journal of Rheumatology JO - J Rheumatol SP - 1 LP - 3 DO - 10.3899/jrheum.190900 VL - 47 IS - 1 AU - YUSUF YAZICI Y1 - 2020/01/01 UR - http://www.jrheum.org/content/47/1/1.abstract N2 - The term metaanalysis was first used in the mid-1970s for describing methods designed to characterize and combine the findings of prior studies to increase statistical power, along with providing quantitative summary estimates, and to identify data gaps and biases1. (In this editorial I will use the term metaanalysis to encompass not only metaanalyses but also systematic reviews and network metaanalyses, because the issues I raise apply to all of them and their variations.) When applied to studies conducted with similar populations and methods, metaanalyses can be useful. However, this is not the case with many metaanalyses where the findings of studies that differ in important ways have been combined, prompting the comment that “they have mixed apples and oranges” — and sometimes “apples, lice, and killer whales — yielding meaningless conclusions”1,2.Combining the results of individual studies potentially increases the total number of participants, and this should mean increased statistical power, yet differences in participant demographics and study methods may actually lead to decreased power owing to variability in the patient characteristics1. This then leads to more difficulty in ascertaining the real effects.Add to this the issue of unpublished research to potentially skew the conclusions, because positive findings get published more often than negative results, starting with the decision to submit them in the first place3. It has been reported that falsified data also make it into metaanalyses4. In one example authors showed that 46% of all metaanalysis publications had their conclusions changed by publications with falsified data and 32% of all the analyses had a considerable change in the outcome5.There has also been … Address correspondence to Dr. Y. Yazici, 333 East 38th St., New York, New York 10016, USA. E-mail: yusuf.yazici{at}nyumc.org ER -