Table 2.

Quality assessment of the included studies according to the National Institute of Health (NIH) quality assessment tool for observational cohort and cross-sectional studies.

Study	C 1	C 2	C 3	C 4	C 5	C 6	C 7	C 8	C 9	C 10	C 11	C 12	C 13	C 14
Paramalingam 2021	Yes	Yes	CD	Yes	No	NA	Yes	NA	Yes	NA	Yes	Yes	Yes	Yes
Leeuwenberg 2020	Yes	Yes	Yes	Yes	No	NA	Yes	No	Yes	No	Yes	No	Yes	No
Albayda 2018	Yes	Yes	Yes	Yes	No	NA	Yes	No	Yes	No	Yes	No	Yes	No
Nodera 2015	Yes	No	CD	Yes	No	NA	Yes	No	Yes	No	Yes	Yes	Yes	No
Noto 2013	Yes	Yes	CD	Yes	No	NA	Yes	NA	Yes	NA	Yes	No	Yes	No

C—criterion; CD—cannot be determined; NA—not applicable; Criterion 1—clear statement of research question and objective; Criterion 2—clear specification and definition of the study population; Criterion 3—participation rate of 50% of eligible persons; Criterion 4—selection of subjects from the same population and time period and application of selection criteria on all subjects uniformly; Criterion 5—justification of sample size; Criterion 6—measurement of exposure before measurement of outcome; Criterion 7—sufficient timeframe to predict an association between exposure and outcome; Criterion 8—examination of different levels of the exposure in relation to the outcome; Criterion 9—clear and valid definition of exposure measures and its consistent implementation on study subjects; Criterion 10—assessment of exposure more than once over time; Criterion 11—clear and valid definition of outcome measures and its consistent implementation on study subjects; Criterion 12—blinding of outcome assessors to exposure status of participants; Criterion 13—loss to follow up being 20% or less; Criterion 14—measurement or statistical adjustment of confounding variables.