Blueberries and Cognitive Ability: A Test of Publication Bias and Questionable Research Practices

Abstract

Accepted in Journals of Gerontology Series A: Biological Sciences and Medical Sciences BLUEBERRIES, COGNITION, AND PUBLICATION BIAS 2 Hein et al (1) published a systematic review of the effects of blueberries on cognitive performance, finding that benefits may be observed for delayed memory, executive functioning, and psychomotor functioning in healthy children, healthy older adults, and/or older adults suffering from mild cognitive impairment (MCI). The purpose of the following analyses was to

Dietary Flavonoids and Human Cognition: A Meta‐Analysis

“…Appropriate sampling should in fact consider a small expected effect size. Indeed, study sample size and other research best practices in the wider field of nutrition and cognition have received commentary, including by Brydges and Gaeta [118] who found publication bias in the blueberry and cognition studies reviewed by Hein et al [119] However, it should be noted that the analysis by Brydges and Gaeta used p-values drawn from only the key findings from the individual studies and were not representative of all reported results in the original papers. A subsequent reanalysis by Whyte et al accounting for all the dependent variables reported in the original source papers found no evidence of publication bias.…”

JPEN Journal Club 75. When the headline does not match the study

“…Those problems included publication bias and an inability to reproduce some of the calculations. 6,7 It may be important to note that both the systematic review and this trial were funded by the Wild Blueberry Association of North America.…”

“…The previously cited systematic review suggesting that there may be benefits to the memory from blueberries 1 also came under criticism for methodologic problems. Those problems included publication bias and an inability to reproduce some of the calculations 6,7 . It may be important to note that both the systematic review and this trial were funded by the Wild Blueberry Association of North America.…”

Errors or Irreproducibility in Effect Size Calculations and Incomplete Reporting of Results in “Systematic Review of the Effects of Blueberry on Cognitive Performance as We Age”

“…In addition, risk of bias assessments within and across studies (#15, 19, and 22) should be included to formally assess the quality and certainty of the research in a standardized manner. Indeed, a recent analysis of the studies included in the review is suggestive of publication bias and/or other questionable research practices (7). Further, 3 of the 11 studies employ crossover designs, which are appropriately described within the text, but the authors mislabel some designs in the Tables and in the discussion: "… all but two studies (39, 45) employed a double-blind crossover, placebocontrolled design….…”