Table 3.
Mediation analysis of racial disparities for TNBC by socioeconomic status, family history, physical activity, anthropometrics and reproductive history
| Estimate | 95% CI lower limit |
95% CI upper limit |
Proportion mediated (95% CI) |
|
|---|---|---|---|---|
| Cardiometabolic risk factorsa (3 vs 0) | 0.48 (0.17–1.25) | |||
| Natural direct effect | 1.40 | 0.89 | 2.19 | |
| Natural indirect effect | 1.26 | 1.01 | 1.58 | |
| Total effect | 1.76 | 1.19 | 2.59 | |
| Physical activity | ||||
| Natural direct effect | 1.94 | 1.53 | 2.46 | –c |
| Natural indirect effect | 1.00 | 0.98 | 1.02 | |
| Total effect | 1.94 | 1.53 | 2.45 | –c |
| Parity | ||||
| Natural direct effect | 1.99 | 1.56 | 2.54 | |
| Natural indirect effect | 0.95 | 0.92 | 0.98 | |
| Total effect | 1.89 | 1.48 | 2.42 | |
| Breastfeeding among parous women (≥ 6 months per child) | 0.03 (0.01–0.04) | |||
| Natural direct effect | 1.97 | 1.55 | 2.52 | |
| Natural indirect effect | 1.01 | 1.00 | 1.02 | |
| Total effect | 2.00 | 1.57 | 2.55 | –c |
| Low socioeconomic status (SES) (2 vs 0)b | ||||
| Natural direct effect | 2.25 | 1.62 | 3.12 | |
| Natural indirect effect | 0.88 | 0.75 | 1.03 | |
| Total effect | 1.98 | 1.48 | 2.63 |
In the mediation analysis, we adjusted for age, family history of breast cancer, different WHI study subcohorts (observational study or clinical trials and different treatment assignments for all 4 clinical trials), cardiometabolic risk factors, physical activity, parity, breastfeeding, and socioeconomic status except for the variable being assessed as a mediator
Metabolic dysfunction was assessed by four cardiometabolic risk factors, including elevated WC, self-reported history of diabetes, high cholesterol, and hypertension. We summed the four components with a total score from 0 to 4. A higher score indicates higher metabolic dysfunction. We collapsed scores of 3 and 4 due to a small sample size in the score of 4
We assigned 1 point for education being high school degree or lower, 1 point for annual family income < $20,000, and 1 point for NSES lower than 20% of the population, and summed for a total score from 0 to 3; scores of 2 and 3 were collapsed. A higher score indicates low SES
Since the natural direct effect and natural indirect effect are in opposite direction, it is not meaningful to estimate the proportion mediated