Table 1.

Quality assessment of included studies using ‘Newcastle–Ottawa Quality Assessment Form for Cohort Studies’ [29]

First author, year of publication, country, study name [ref]	Selectiona				Comparabilitya	Outcomea
	1	2	3	4b	1c	1	2d	3
Sleep patterns (k = 7)
Bach, 2020, UK [34]	PY	Y	Y	PN	Y	Y	Y	Y
Liang, 2019, China, Guangzhou Breast Cancer Study [37]	PY	Y	PY;PN	PN	Y	PY	PY	Y
Mansano-Schlosser, 2017, Brazil [36]	PN	Y	PY	PN	PN	Y	N	Y
Marinac, 2017, USA, WHEL [31]	PY	Y	PN	PN	Y	Y	Y	Y
Trudel-Fitzgerald, 2017, USA, NHS [32]	PY	Y	PN	PN	Y	Y	Y	Y
Hahm, 2014, USA [38]	PN	Y	PY	N	Y	Y	Y	Y
Palesh, 2014, USA [33]	PN	Y	Y	N	Y	Y	Y	Y
Eating behaviours (k = 1)
Marinac, 2016, USA, WHEL [35]	PY	Y	PY	PN	Y	Y	Y	Y

^aSelection (1. Representativeness of the exposed cohort, 2. Selection of the non-exposed cohort, 3. Ascertainment of exposure, 4. Demonstration that outcome of interest was not present at start of study); Comparability (1. Comparability of cohorts based on the design or analysis controlled for confounders); Outcomes (1. Assessment of outcome, 2. Was follow-up long enough for outcomes to occur, 3. Adequacy of follow-up of cohorts)

^bThe criterion for absence of outcome at the start of the study was considered met if the cohort excluded those with stage IV/metastatic disease

^cAge or menopausal status, breast cancer stage or grade, and breast cancer treatment were identified as the key confounders to be considered in analysis