Table 3. Newcastle-Ottawa scale scores for included studies.

Newcastle–Ottawa scale case-control studies
					Comparability of cases and controls on the basis of the design or analysis
Study ID	Is the case definition adequate?	Are the cases representative?	Selection of controls adequate	Definition of controls adequate	a) Study controls for the most important factor	b) Study controls for important additional factors	Ascertainment of exposure adequate	Same method of ascertainment for cases and controls	Non-response rate adequate	Total score /9
Ferencz 1980	yes	yes	yes	yes	yes	yes	yes	yes	yes	9
Gal 1972	unclear	unclear	yes	yes	yes	yes	yes	yes	unclear	6
Greenberg 1977	yes	yes	yes	yes	yes	yes	unclear	yes	yes	8
Janerich 1974	no	yes	yes	no	yes	no	yes	yes	unclear	5
Janerich 1977	yes	yes	unclear	yes	yes	yes	yes	unclear	yes	7
Hellstrom 1976	yes	unclear	no	yes	yes	no	unclear	yes	unclear	4
Lammer 1986	yes	yes	unclear	yes	yes	yes	yes	yes	no	7
Laurence 1971	yes	unclear	unclear	yes	no	unclear	unclear	unclear	unclear	2
Levy 1973	yes	yes	no	yes	yes	no	unclear	unclear	unclear	4
Nora 1975	yes	yes	yes	yes	yes	no	yes	yes	yes	8
Nora 1978 case control 1	yes	yes	yes	no	yes	yes	yes	yes	yes	8
Nora 1978 case control 2 and 3	yes	yes	yes	no	yes	yes	yes	yes	unclear	7
Polednak 1983	yes	yes	yes	yes	yes	no	unclear	yes	unclear	6
Rothman 1979	yes	yes	no	no	no	yes	yes	yes	unclear	5
Sainz 1987	unclear	yes	yes	unclear	yes	yes	unclear	yes	unclear	5
Tummler 2014	yes	no	no	no	no	no	no	yes	yes	3
Newcastle–Ottawa scale cohort studies
					Comparability of cases and controls on the basis of the design or analysis
	Are the participants representative of the exposed cohort?	Is the non- exposed cohort similar to the exposed?	Is the ascertainment of exposure accurate?	Is there evidence that the outcome of interest was not present at start of study?	a) Study controls for the most important factor	b) Study controls for important additional factors	Was the assessment of outcome adequate?	Was follow-up long enough for outcomes to occur?	Was there adequacy of follow up of cohorts?	Total score /9
Fleming 1978	yes	unclear	unclear	yes	unclear	unclear	unclear	yes	unclear	3
Goujard 1979	yes	yes	unclear	yes	yes	no	unclear	yes	yes	6
Hadjigeorgiou 1982	yes	yes	yes	yes	no	yes	yes	yes	unclear	7
Haller 1974	unclear	unclear	unclear	yes	no	no	unclear	yes	unclear	2
Kullander 1976	yes	yes	yes	yes	yes	unclear	yes	yes	yes	8
Meire 1978	yes	no	yes	yes	yes	no	unclear	yes	yes	6
Michaelis 1983	yes	yes	yes	yes	yes	yes	yes	yes	yes	9
Roussel 1968	yes	yes	yes	yes	no	no	unclear	yes	yes	6
Rumeau- Rouquette 1978	yes	unclear	yes	yes	yes	yes	yes	yes	no	7
Torfs 1981	yes	yes	yes	yes	yes	yes	yes	yes	yes	9