Table 3.

Critical appraisal of included studies

	Malek et al. 2015	Sajjad et al. (2012)	Bookari et al. (2017)	Bojar et al. (2006)	Gao et al. (2013)	Zhang et al. (2017)	Pick et al. (2005)	Panwar et al. (1998)	Olmedo–Requena et al. (2018)	Okubo et al. (2010)	Mishra et al. (2014)	Jood et al. (2002)	Hure et al. (2008)	Dahiya (2002)	Pinto et al. (2008)	de Weerd et al. (2003)	Liu et al. (2015)	Yang et al. (2016)
Was the research question or objective in this paper clearly stated?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Was the study population clearly specified and defined?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	CD	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Was the participation rate of eligible persons at least 50%?	Yes	CD	Yes	Yes	Yes	Yes	Yes	NR	Yes	No	NR	NR	No	NR	Yes	Yes	NR	Yes
Were all the subjects selected or recruited from the same or similar populations (including the same time period)? Were inclusion and exclusion criteria for being in the study prespecified and applied uniformly to all participants?	Yes	CD	Yes	CD	NR	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	CD	Yes	Yes	Yes	Yes
Was the sample size justification, power, description, or variance and effect estimates provided?	Yes	NR	Yes	Yes	Yes	NR	NR	NR	NR	Yes	NR	NR	NR	NR	NR	NR	Yes	NR
For the analyses in this paper, were the exposure(s) of interest measured prior to the outcome(s) being measured?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Was the timeframe sufficient so that one could reasonably expect to see an association between exposure and outcome if it existed?	Yes	No	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	No	Yes
For exposures that can vary in amount or level, did the study examine different levels of the exposure as related to the outcome (e.g., categories of exposure or exposure measured as continuous variable)?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Were the exposure measures (independent variables) clearly defined, valid, reliable, and implemented consistently across all study participants?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes
Was the exposure (S) assessed more than once over time?	No	No	No	Yes	No	No	Yes	Yes	Yes	No	No	Yes	No	No	Yes	No	No	No
Were the outcome measures (dependent variables) clearly defined, valid, reliable, and implemented consistently across all study participants?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Were the outcome assessors blinded to the exposure status of participants?	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Was loss to follow‐up after baseline 20% or less?	NR	NR	NR	NR	NA	Yes	Yes	NA	Yes	NR	NR	NR	NR	NR	Yes	No	NR	Yes
Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure (S) and outcome (S)?	Yes	Yes	Yes	Yes	No	Yes	Yes	CD	Yes	Yes	CD	CD	Yes	NR	Yes	Yes	Yes	Yes
Quality rating (Good, Fair, Poor)	Good	Fair	Good	Fair	Fair	Good	Good	Fair	Good	Good	Fair	Fair	Good	Fair	Good	Good	Fair	Good
Rater #1 initials:	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC	CC
Rater #2 initials:					AS				AS			ML					ML
Additional comments (If poor, please state why):
Was the research question or objective in this paper clearly stated?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Was the study population clearly specified and defined?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	CD	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes

Abbreviations: AS, Dr Amie Steel; CC, Cherie Caut; CD, cannot determine; ML, Dr Matthew Leach; NA, not applicable; NR, not reported.