Correlation between breast cancer and lifestyle within the Gulf Cooperation Council countries: A systematic review

Table 8 Critical appraisal of observational cohort and cross-sectional studies using the National Institutes of health study quality checklists (continued Table 7)

	Al Saeed et al[42], 2015	Al-Eisa and Al-Sobayel[36], 2012	Al-Habsi et al[32], 2015	Al-Malki et al[38], 2003	Al-Shammari et al[33], 2015	Alabdulkarim et al[81], 2018	Albawardi et al[27], 2017	Alsaeed et al[43], 2017	Bener et al[45], 2017	Carter et al[34], 2004	Khalid[37], 2007	Rudat et al[44], 2012	Sayegh et al[35], 2016
Were the outcome measures (dependent variables) clearly defined, valid, reliable and implemented consistently across all study participants?	NR	Y	Y	NA	Y	Y	Y	Y	Y	Y	Y	N	Y
Were the outcome assessors blinded to the exposure status of the participants	N	CD	N	N	N	CD	N	N	Y	Y	Y	N	N
Was loss to follow-up after baseline 20% or less?	NR	NA	NA	NA	NA	N	Y	NA	NA	NA	NA	NA	Y
Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure and outcome?	Y	N	N	Y	N	Y	Y	Y	Y	Y	Y	N	N
Quality rating	Poor	Poor	Poor	Poor	Poor	Fair	Good	Good	Fair	Fair	Good	Poor	Poor
Additional comments	Selection bias, no blinding	Confounding bias	Confounding and recall bias	Selection bias	Selection and confounding bias							Confounding and selection bias	Confounding and recall bias for BMI

Y: Yes; N: No; CD: Cannot determine; NA: Not applicable; NR: Not reported; BMI: Body mass index; PA: Physical activity.