TABLE 2.

Quality assessment of the included cohort studies.

Study design	Selection (✰ ✰ ✰ ✰)	Comparability (✰ ✰)	Exposure or Outcome (✰ ✰ ✰)	Stars	Quality scores
Cohort studies	1) Representativeness of the exposed cohort? ✰	1) Study controls for the most important factor? ✰	1) How to ascertain outcome? ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰ (9)	High quality: 8–9 stars, Moderate quality: 6–7 stars.
	2) Selection of the non-exposed cohort? ✰	2) Study controls for any additional factors? ✰	a) Independent blindness
	3) Evaluating exposure? ✰		b) Record linkage
	4) Outcomes of interest were not present at study start? ✰		2) Follow-up till outcomes happened? ✰
			3) Adequacy of follow up? ✰
Included cohort studies
Miyake, et al. (25)	1) × : female cohort, 2) ✰, 3) × , 4) ✰	1) ✰, 2) ✰	1) × , 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰	Moderate
Lucas, et al. (19)	1) × : female cohort, 2) ✰, 3) ✰, 4) ✰	1) ✰, 2) ✰	1) ✰, 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰	High
Ruusunen, et al. (22)	1) × : male cohort; 2) ✰, 3) ✰, 4) ✰	1) ✰; 2) ✰	1) ✰, 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰	High
Kesse-Guyot, et al. (18)	1) ✰, 2) ✰, 3) × , 4) × : no statement	1) ✰; 2) ✰	1) × , 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰	Moderate
da Rocha and Kac (20)	1) × : female cohort, 2)✰, 3) ✰, 4) × : no statement	1) ✰; 2) ✰	1) × , 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰	Moderate
Chong, et al. (26)	1) × : female cohort, 2) ✰, 3) ✰, 4) ✰	1) ✰, 2) ✰	1) ×, 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰	High
Matsuoka, et al. (28)	1) ✰, 2) ✰, 3) ✰, 4) × : no statement	1) ✰, 2) ✰	1) ✰, 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰	High
Pinto, et al. (23)	1) × : female cohort, 2) ✰, 3) ✰, 4) ✰	1) ✰, 2) ✰	1) ✰, 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰	High
Horikawa et al. (27)	1) ✰, 2) ✰, 3) ✰, 4) ✰	1) ✰, 2) ✰	1) × , 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰	High
Hoge et al. (29)	1) × : female cohort, 2)✰, 3) ✰, 4) × : no statement	1) ✰, 2) ✰	1) × , 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰	Moderate
Thesing et al. (24)	1) ✰, 2) ✰, 3) ✰, 4) ✰	1) ✰, 2) ✰	1) × , 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰	High
Mongan et al. (30)	1) ✰, 2) ✰, 3) ✰, 4) ✰	1) ✰, 2) ✰	1) × , 2) ✰, 3) ✰	✰ ✰ ✰ ✰ ✰ ✰ ✰ ✰	High