References | Sample sizea | Power and sample size calculation for mediation analysis | Exposure-mediator interaction in the model | Power and sample size calculation for interaction analysis | Lack of power mentioned as a non-causal explanation of findings |
---|---|---|---|---|---|
Studies with negative findings | |||||
Freeman et al. [28] | N = 51 for adjusted and n = 54 for unadjusted analysis | 80 % power to detect large indirect effects (Fritz M, Mackinnon DP. Required sample size to detect the mediated effect) | Not reported | Not applicable | Limited power to detect whether mediated effects were statistically significant |
Jackson et al. [29] | N = 26,197 | Not reported | ✓ | No | No |
Kositsawat et al. [30] | N = 1765 | Not reported | Not reported | Not applicable | No |
Louwies et al. [31] | N = 55 | Not reported | Not reported | Not applicable | Called for cautious interpretation given small sample size |
Mendola et al. [33] | Varied by outcomes (i.e. 1 study site did not report infant apnea) | Not reported | ✓ | No | No |
Studies with positive findings | |||||
Banack et al. [26] | N = 7212 | Not reported | ✓ | No | No |
D’Amelio et al. [27] | N = 37 | 80 % power, two-sided significance level of 0.05, to detect differences in uOC greater than 1.71 (t test on log-scale) | ✓ | No | Acknowledged small sample size as a limitation |
Lu et al. [32] | N = 58,322 for metabolic N = 19,572 for fibrinogen | Not reported | ✓ | No | No |
Messerlian et al. [34] | All singleton births (n = 18,147); only first births (n = 8651) | Not reported | Not reported | Not applicable | Limited power mentioned; limited sample size to evaluate spontaneous and induced preterm birth separately |
Raghavan et al. [35] | Varied by mediators (n = 2159 for diet score; and n = 2098 for physical activity index) | Not reported | Not reported | Not applicable | Lack of power to examine the association in the mediation framework |
Rao et al. [36] | N = 433 | Not reported | X | No | No |
Song et al. [37] | Varied by mediators (biomarkers) | Not reported | ✓ | No | Despite some significant mediation by several biomarkers, the sample size may still not be large enough to provide more precise estimates or to detect mediation by other potential factors with smaller mediation effects |
Xie et al. [38] | N = 167 | Not reported | X | No | Small sample size acknowledged |