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84 Chapter 3 Quality assessment Quality assessment tools from the NHLBI were used to assess the methodological quality of the included studies (Tables 5 and 6). Outcomes were used to assess the internal validity and risk of bias for each study and the overall quality was rated as good, fair, or poor. Only one study had an overall rating of good. 9 Four studies were rated fair 12,13,21,29 , and the remaining three articles were rated poor. 26,28,30 In general, studies lacked sample size justification, some studies did not differentiate between overweight and obesity and all but one study did not adjust for key potential confounding variables. In addition, some items of the quality assessment tools were not reported across studies (Tables 5 and 6). TABLE 5. NHLBI quality assessment tool for observational cohort and cross-sectional studies Fishman et al . v/d Baan- Slootweg et al . Phatak et al. Costa et al . Koppen et al . 1. Was the research question or objective in this paper clearly stated? Yes Yes Yes Yes Yes 2. Was the study population clearly specified and defined? Yes Yes Yes Yes Yes 3. Was the participation rate of eligible persons at least 50%? Yes Yes CD CD Yes 4. 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 Yes 5. Was a sample size justification, power description, or variance and effect estimates provided? No No No No No 6. For the analyses in this paper, were the exposure(s) of interest measured prior to the outcome(s) being measured? Yes Yes No No No 7. 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 8. 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)? No No Yes No Yes 9. Were the exposure measures (independent variables) clearly defined, valid, reliable, and implemented consistently across all study participants? CD CD Yes No Yes 10. Was the exposure(s) assessed more than once over time? No No No No No 11. Were the outcome measures (dependent variables) clearly defined, valid, reliable, and implemented consistently across all study participants? Yes Yes Yes Yes Yes 12. Were the outcome assessors blinded to the exposure status of participants? NR NR NR NR NR 13. Was loss to follow-up after baseline 20% or less? NA NA NA NA NA 14. Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)? No No Yes No No Rating Fair Fair Good Poor Fair Available at: http://www.nhlbi.nih.gov/health-pro/guidelines/in-develop/cardiovascular-risk-reduction/tools/cohort. CD, cannot determine; NA, not applicable; NR, not reported.