Sample size determination. We estimated that a sample of at least 500 was required to achieve 80% power at an a = 0.05 to reject a model of the specified complexity ( Figure 3 ) if the model fit index Root Mean Square Error of Approximation (RMSEA) exceeded 0.08 [54, 55] . To allow for a response rate ,60% in the follow-up and the baseline surveys, we need to target at least 1,389 subjects in the baseline survey.