Table 3.

Risk of bias (quality) assessment of 7 observational (cross-sectional) studies using NIH Quality Assessment.

Criteria	Bricknell et al. [14]	Fetterman et al. [15]	Oliveri et al. [16]	Podzolkov et al. [17]	Rader et al. [18]	Sahota et al. [19]	Vindhyal et al. [20]
Was the research question or objective in this paper clearly stated?	Yes	Yes	Yes	Yes	No	Yes	Yes
Was the study population clearly specified and defined?	Yes	Yes	Yes	Yes	No	Yes	Yes
Was the participation rate of eligible persons at least 50%?	Yes	Yes	No	Yes	Not reported	Yes	Not reported
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?	Yes	Yes	Yes	Yes	Not reported	Yes	Yes
Was a sample size justification, power description, or variance and effect estimates provided?	No	No	Yes	No	No	No	No
For the analyses in this paper, were the exposure(s) of interest measured prior to the outcome(s) being measured?	No	No	No	No	No	No	No
Was the timeframe sufficient so that one could reasonably expect to see an association between exposure and outcome if it existed?	No	No	No	No	No	No	No
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)?	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable
Were the exposure measures (independent variables) clearly defined, valid, reliable, and implemented consistently across all study participants?	No	No	No	No	No	No	No
Was the exposure(s) assessed more than once over time?	No	No	No	No	No	No	No
Were the outcome measures (dependent variables) clearly defined, valid, reliable, and implemented consistently across all study participants?	No	Yes	Yes	Yes	Yes	Yes	No
Were the outcome assessors blinded to the exposure status of participants?	Not applicable	Yes	Yes	Yes	Not reported	Not reported	Not applicable
Was loss to follow-up after baseline 20% or less?	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable	Not applicable
Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)?	Yes	Yes	Yes	Not applicable	Not applicable	Not applicable	Yes
Overall quality rating	Fair	Good	Good	Fair	Poor	Fair	Poor