Table 3 Study quality and risk of bias assessment. Studies were assessed using items from the Newcastle Ottawa Scale and the Cochrane Collaboration’s risk of bias assessment tool, addressing key methodological criteria relevant to included studies. (+ indicates yes; −, no; ?, uncertain)
Demographics reported | Medical comorbidities reported | Excluded medical comorbidities | Non-retrospective design | Standardized criteria used for diagnosis | Reported medication use | Excluded use of antioxidants | Representative population | ||
|---|---|---|---|---|---|---|---|---|---|
First author | Year | General risk of bias items | |||||||
Brain GSH | |||||||||
Duffy | 2014 | + | - | + | + | + | + | - | + |
Mandal | 2015 | + | - | + | + | + | - | - | + |
Marjanska | 2019 | + | - | + | + | + | - | - | + |
Mullins | 2018 | + | - | + | + | + | - | - | ? |
Oeltzschner | 2019 | + | - | + | + | + | - | - | + |
Shukla | 2019 | + | - | + | + | + | - | - | + |
Blood GSH | |||||||||
Arslan | 2016 | + | - | + | + | + | - | - | + |
Aybek | 2007 | + | - | - | + | + | - | - | + |
Bai | 2018 | - | - | + | + | + | - | - | + |
Baldeiras | 2008 | + | ? | + | + | + | + | + | + |
Bermejo | 2008 | ? | - | + | + | + | - | - | ? |
Bicikova | 2004 | + | + | + | + | + | - | - | + |
Gironi | 2011 | + | - | + | + | + | + | + | + |
Gironi | 2014 | + | - | + | + | + | - | - | + |
Gubandru | 2013 | + | + | + | + | ? | + | + | ? |
Fernandes | 1999 | + | - | + | ? | + | - | - | + |
Hernanz | 2007 | + | - | - | + | + | - | - | + |
Klimiuk | 2019 | + | + | + | + | ? | - | + | + |
Kosenko | 2016 | + | - | - | + | + | - | - | + |
Krishnan | 2014 | + | - | + | + | + | - | - | + |
Kurup | 2003 | - | + | - | + | + | ? | - | ? |
Liu | 2005 | + | - | + | + | + | - | - | + |
McCaddon | 2003 | + | + | + | + | + | - | - | + |
Martinez de Toda | 2019 | + | - | + | + | + | - | - | + |
Mohamed | 2019 | + | + | + | + | + | + | - | + |
Prendecki | 2018 | + | - | - | + | + | + | - | + |
Puertas | 2012 | + | - | + | + | + | - | + | + |
Rani | 2017 | + | - | + | + | + | - | - | + |
Riveron | 2007 | - | - | + | + | + | - | + | + |
Sadhu | 2014 | - | + | + | + | + | ? | - | ? |
Tabet | 2002 | + | - | - | + | + | - | - | + |
Vida | 2018 | + | - | + | + | + | - | - | + |
Yuan | 2016 | + | - | + | + | + | - | + | + |
Representative population | Cognitively intact control group | Community controls | Similarly aged controls | Similar gender proportions in controls | Similar in other characteristics | Assessed for cognitive impairment | Likelihood of high overall quality | ||
|---|---|---|---|---|---|---|---|---|---|
First author | Year | Control items | |||||||
Brain GSH | |||||||||
Duffy | 2014 | + | + | + | + | + | + | + | + |
Mandal | 2015 | + | + | + | + | + | + | + | + |
Marjanska | 2019 | + | + | ? | + | - | ? | + | + |
Mullins | 2018 | ? | ? | ? | + | + | ? | - | - |
Oeltzschner | 2019 | + | + | + | - | - | ? | + | + |
Shukla | 2019 | ? | ? | + | + | - | ? | - | - |
Blood GSH | |||||||||
Arslan | 2016 | ? | + | - | + | - | + | + | - |
Aybek | 2007 | ? | + | - | + | + | ? | - | - |
Bai | 2018 | + | + | - | ? | ? | ? | - | - |
Baldeiras | 2008 | + | + | ? | + | - | + | + | + |
Bermejo | 2008 | ? | + | - | + | ? | ? | - | - |
Bicikova | 2004 | + | + | ? | + | + | + | + | + |
Gironi | 2011 | + | + | + | - | + | ? | + | + |
Gironi | 2014 | + | + | - | + | - | ? | + | + |
Gubandru | 2013 | + | ? | ? | + | + | ? | - | + |
Fernandes | 1999 | + | + | ? | - | + | ? | + | - |
Hernanz | 2007 | + | + | ? | + | + | + | + | + |
Klimiuk | 2019 | + | + | - | + | + | + | + | + |
Kosenko | 2016 | + | ? | ? | + | - | + | - | - |
Krishnan | 2014 | + | + | ? | + | + | + | + | + |
Kurup | 2003 | + | ? | + | ? | ? | ? | - | - |
Liu | 2005 | + | + | + | + | + | ? | + | + |
McCaddon | 2003 | + | + | + | + | + | + | + | + |
Martinez de Toda | 2019 | + | + | - | + | + | + | + | + |
Mohamed | 2019 | + | + | ? | + | + | + | + | + |
Prendecki | 2018 | - | + | ? | + | + | ? | + | + |
Puertas | 2012 | ? | + | - | + | + | ? | - | - |
Rani | 2017 | + | + | ? | + | + | ? | + | + |
Riveron | 2007 | + | ? | ? | ? | ? | ? | ? | - |
Sadhu | 2014 | ? | ? | ? | ? | ? | ? | + | - |
Tabet | 2002 | + | + | + | - | - | ? | + | - |
Vida | 2018 | ? | + | - | + | - | ? | + | - |
Yuan | 2016 | + | ? | + | + | + | + | - | + |