Long-Term Sleep Duration as a Risk Factor for Breast Cancer: Evidence from a Systematic Review and Dose-Response Meta-Analysis

Table 1

Characteristics of studies and participants included in meta-analysis.

Author	Year	Country	Study	Number of participants	Follow-up/investigated years	Age at baseline	Postmenopausal (%)	Study design
Xiao et al. [9]	2016	America	Southern community cohort study	42953	2002–2009	52.18	66.70%	Cohort study
Hurley et al. [10]	2015	America	California teachers study	101609	“1995-1996” to 2011	52.00	58.28%	Cohort study
Wang et al. [11]	2014	China	Guangzhou breast cancer study	1454	2010–2012	47.50	37.14%	Case-control study
Vogtmann et al. [12]	2013	America	Women’s health initiative	110011	1992–2007	62.91	100%	Cohort study
Wu et al. [13]	2012	Singapore	Singapore Chinese health study	34028	“1993–1998” to 2010	45–74	92.73%	Nested case-control study
Girschik et al. [14]	2012	Australia	Breast cancer environment and employment study	2828	2009–2011	18–80	88.79%	Case-control study
Kakizaki et al. [15]	2008	Japan	Ohsaki national health insurance cohort study	23995	1994 to “1995–2003”	60.76	65.42%	Cohort study
Pinheiro et al. [16]	2006	America	Nurses’ health study	77418	“1986, 2000” to “1986, 2002”	52.94	56.87%	Cohort study
McElroy et al. [17]	2005	America	US case-control study	9347	1997–1999	20–69	54.98%	Case-control study
Verkasalo et al. [18]	2005	Finland	Finnish twin cohort	12222	“1975, 1981” to “1976–1996”	36.50	—	Cohort study