Table 2.
Quality assessment of included cohort and cross-sectional studies using the NIH quality assessment tool.
| Author, YOP | Q1 | Q2 | Q3 | Q4 | Q5 | Q6 | Q7 | Q8 | Q9 | Q10 | Q11 | Q12 | Q13 | Q14 | Overall Quality |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wolff et al. [17] | Y | N | Y | Y | NR | Y | N | N | N | N | Y | NR | NR | N | Fair |
| Brazerol et al. [30] | Y | Y | Y | Y | NR | Y | N | N | N | N | Y | NR | NR | N | Fair |
| El Maftouhi et al. [31] | Y | N | Y | Y | NR | Y | N | N | N | N | Y | NR | Y | N | Fair |
| Hasegawa et al. [16] | Y | Y | Y | Y | NR | Y | Y | Y | N | N | Y | NR | Y | N | Good |
| Hasegawa et al. [19] | N | Y | Y | Y | NR | Y | NR | N | N | N | Y | NR | NR | N | Fair |
| Mahmoudinezhad et al. [21] | Y | Y | N | Y | NR | Y | Y | Y | N | N | Y | NR | NR | Y | Fair |
| Murata et al. [20] | Y | Y | N | Y | NR | Y | NR | Y | N | N | Y | NR | NR | N | Fair |
| Wen et al. [14] | Y | Y | N | N | NR | Y | NR | N | N | N | Y | NR | NR | N | Fair |
Quality was rated as poor (if a study scored 0–4 out of 14 questions), fair (if a study scored 5–10 out of 14 questions), or good (if a study scored 11–14 out of 14 questions).
YOP year of publication, Y yes, N no, NR not reported, NIH National Institute of Health.
Q1: Was the research question or objective in this paper clearly stated? Q2: Was the study population clearly specified and defined? Q3: Was the participation rate of eligible persons at least 50%? Q4: Were all the subjects selected or recruited from the same or similar populations (including the same time period)? Were inclusion and exclusion criteria for being in the study prespecified and applied uniformly to all participants? Q5: Was a sample size justification, power description, or variance and effect estimates provided?’ Q6: For the analyses in this paper, were the exposure(s) of interest measured prior to the outcome(s) being measured? Q7: Was the timeframe sufficient so that one could reasonably expect to see an association between exposure and outcome if it existed? Q8: For exposures that can vary in amount or level, did the study examine different levels of the exposure as related to the outcome (e.g., categories of exposure, or exposure measured as continuous variable)? Q9: Were the exposure measures (independent variables) clearly defined, valid, reliable, and implemented consistently across all study participants? Q10: Was the exposure(s) assessed more than once over time? Q11: Were the outcome measures (dependent variables) clearly defined, valid, reliable, and implemented consistently across all study participants? Q12: Were the outcome assessors blinded to the exposure status of participants? Q13: Was loss to follow-up after baseline 20% or less? Q14: Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)?