tically signifi cant result. In a separate analysis, his team found that the main fi ndings of only one of six highly cited observational studies could be replicated; the conclusions from the other fi ve were refuted. “The combination of selec tive reporting and multiplicity of analysis undermines the credibility of epidemiological studies,” Ioannidis said at the an nual meeting of the American...

Based on JASA (2010) 105, 692-702, Biometrics (2011) 67, 1017-1027, AOAS (2012) 6, 83-105, Biometrika (2012) 99, 763-774, JASA (2015) 110, 205-217. Application in Zubizarreta et al (2014).

Correspondence to Professor Maarten Boers; eb@vumc.nl In this issue, Apostopoulos et al report yet another observational study on the association of glucocorticoid (GC) treatment with a bad outcome, in this case damage accrual in SLE. Unsurprisingly, the association is present, and ‘independent’ of potential confounders. Unsurprisingly, the authors argue for a causal relationship. So what is ne...

The PLOS Medicine Editors endorse four measures to ensure transparency in the analysis and reporting of observational studies. Please see later in the article for the Editors' Summary.

Background and Purpose—The relationship between elevated lipoprotein (a) levels[Lp(a)] and stroke is controversial. We systematically reviewed the literature to determine whether Lp(a) is a risk factor for stroke. Methods—We searched MEDLINE (1966 to 2006), EMBASE (1974 to 2006), and Google scholar for articles on Lp(a) and cerebrovascular disease. From potentially relevant references retrieved...

Basic research suggests that oxidative stress may play an important role in many chronic diseases and provides plausible mechanisms by which natural antioxidants such as vitamin E may delay or prevent steps in atherogenesis. Dietary research has shown that those who consume higher amounts of fruits and vegetables have lower rates of heart disease and stroke, raising the possibility that antioxi...