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

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

	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
Was the research question or objective clearly stated?	Y	Y	Y	N	N	N	Y	Y	Y	Y	Y	N	Y
Was the study population clearly specified and defined?	Y	N	Y	N	Y	Y	Y	Y	Y	Y	Y	Y	Y
Was the participation rate of eligible persons at least 50%?	CD	Y	Y (but N for accelerometer)	Y	Y	Y	Y	Y	Y	Y	Y	NA	NA
Were all subjects selected or recruited from the same or similar populations? Were inclusion/exclusion criteria prespecified?	N	Y	Y	N	Y	Y	Y	Y	Y	Y	Y	Y	Y
Was a sample size justification, power description or variance and effect estimates provided?	N	N	N	N	Y	N	Y	Y	Y	Y	Y	N	N
Was the exposure of interest measured prior to the outcome being measured?	Y	N	N	N	N	Y	N	Y	N	N	N	N	Y
Was the timeframe sufficient for an association to be seen?	Y	N	N	N	N	Y	N	N	N	N	N	N	Y
For exposures that can vary in amount or level, did the study examine different levels of the exposure as related to the outcome?	Y	N	Y	NA	Y	NA	Y	NA	Y	Y	Y	Y	Y
Were the exposure measures (independent variables) clearly defined, valid and reliable and implemented consistently across all study participants?	Y	Y	Y	Y	Y	Y	Y	CD	Y	Y	Y	Y	Y
Was the exposure measured more than once over time?	N	Y	Y	N	N	Y	N	N	N	N	N	N	Y

Available online at https://www.nhlbi.nih.gov/health-topics/study-quality-assessment-tools. Y: Yes; N: No; CD: Cannot determine; NA: Not applicable; NR: Not reported; BMI: Body mass index; PA: physical activity.