Table 1.

Case control study features of hair colorant use and NHL

Study	Region	Research period	Gender	Age, years	Source of cases	Source of control group	Cases/ controls, n	NHL evaluation criteria	Hair colorant use evaluation standard	Adjustment factor	Newcastle- Ottawa Scale quality score
Schroeder[15], 2002	USA	1980–1983	M	>30	Iowa State Health Registration Center;Occupational and Environmental Health Research Center of the University of Minnesota	General population	182/1,245	Pathological diagnosis; case history	Questionnaire survey	Age; gender; race	5
Benavente[16], 2005	Spain	1998–2002	M/F	NR	3 pathological diagnosis centers in Spain	Inpatients	574/616	Pathological diagnosis	Face-to-face survey	Gender; age; medication history	6
Cantor [17], 1988	USA	1980–1983	M/F	>30	Cooperative Groupof Pathology among several cities in Iowa and Minnesota	General population	622/1,245	Pathological diagnosis	Questionnaire survey	Age; race; occupation	4
Chiu [18], 2004	USA	1980–1983	M	NR	Hospitals and pathological diagnosis centers of Iowa and Minnesota	General population	907/1,926	Pathological diagnosis; case history	Telephone follow-up	Smoking history; gender	6
Zahm [19], 1992	USA	1980–1986	F	>21	Lymphoma ResearchGroup of Nebraska	General population	441/1,432	Pathological diagnosis; case history	Telephone follow-up	Age; gender; race	5
Holly [20], 1998	USA	1991–1995	M/F	21–74	Pathological registrations from 6 hospitals in San Francisco	General population	1,593/2,515	Case history	Telephone follow-up	Age; gender; race	6
Miligi [21], 2005	Italy	1991–1993	M/F	20–74	11 cities in Italy	General population	611/828	Case history	Face-to-face survey	Smoking history; gender; age; occupation	7
Tavani [7], 2005	Italy	1985–1997	M/F	14–79	Two provincial pathological centers on the east of Italy	Inpatients	446/1,295	Pathological diagnosis	Questionnaire survey	Smoking history; drinking history; age	6
de Sanjosé[22], 2006	Europe	1998–2002	M/F	NR	Cooperative Group of Pathology in Czech Republic, France, Germany, Ireland, Italy, and Spain	Inpatients	1,702/2,417	Pathological diagnosis	Face-to-face survey
Morton [6], 2007	USA	1998–2000	F	NR	Epidemiological investigation institutions in 4 cities	General population	1,321/1,057	Pathological diagnosis; case history
Zhang [23], 2004	USA	1996–2000	F	21–84	Cancer Research Center of Yale University; Connecticut State Public Health Unit	General population	601/717	Pathological diagnosis
Wong [24], 2010	China	2003–2008	M/F	>18	Collaborations among 29 hospital-sin Shanghai	Inpatients	649/1,298	Pathological diagnosis
Sangrajrang [25], 2011	Thailand	2007–2009	M/F	17–81	3 cancer research institutes in Thailand	Inpatients	390/422	Pathological diagnosis; case history	Face-to-face survey

NR, not reported; NHL, non-Hodgkin's lymphoma.