Table 3.
Hazard ratios and 95% confidence intervals for the association of the 2-year post-diagnosis lifestyle score with all-cause mortality, breast cancer-mortality, and breast cancer recurrence.
| Complete Case Analysis | |||||
|---|---|---|---|---|---|
| Model 1a | Model 2b | ||||
| # Events | HR (95% CI) | # Events | HR (95% CI) | ||
| All-Cause Mortality | |||||
| Score tertile (range) | 1 (0–7) | 132 | 1.00 (–) | 108 | 1.00 (–) |
| 2 (8–10) | 99 | 0.79 (0.61, 1.03) | 88 | 0.91 (0.69, 1.22) | |
| 3 (11–18) | 59 | 0.63 (0.46, 0.85) | 46 | 0.72 (0.50, 1.03) | |
| Continuousc, per 2-point increase | 0.86 (0.80, 0.94) | 0.90 (0.82, 0.98) | |||
| Breast Cancer-Specific Mortality | |||||
| Score tertile (range) | 1 (0–7) | 49 | 1.00 (–) | 42 | 1.00 (–) |
| 2 (8–10) | 20 | 0.47 (0.28, 0.79) | 17 | 0.50 (0.28, 0.88) | |
| 3 (11–18) | 11 | 0.40 (0.21, 0.78) | 11 | 0.65 (0.32, 1.31) | |
| Continuousc, per 2-point increase | 0.75 (0.64, 0.87) | 0.79 (0.67, 0.95) | |||
| Breast Cancer Recurrence | |||||
| Score tertile (range) | 1 (0–7) | 55 | 1.00 (–) | 49 | 1.00 (–) |
| 2 (8–10) | 64 | 1.07 (0.74, 1.53) | 56 | 1.10 (0.74, 1.62) | |
| 3 (11–18) | 57 | 1.06 (0.73, 1.55) | 47 | 1.09 (0.72, 1.66) | |
| Continuousc, per 2-point increase | 1.00 (0.90, 1.11) | 0.98 (0.88, 1.10) | |||
Abbreviations: HR, hazard ratio; CI, confidence interval
Model 1 adjusts for age only. Mortality cohort (n= 1,964); Recurrence cohort (n=1,924).
Model 2 adjusts for age, tumor stage, ER status, chemotherapy, Herceptin, radiation, comorbidities, smoking status, income, and education level. Observations were additionally excluded due to missing covariates in the mortality cohort (n=228) and the recurrence cohort (n = 219). Mortality cohort (n= 1,736); Recurrence cohort (n=1,705).
We examined the potentially non-linear relationships between the lifestyle score and the outcomes of interest non-parametrically by fitting models using restricted cubic splines. We tested non-linearity using the likelihood ratio test, comparing a model with only the linear term for the lifestyle score to the model with the linear and cubic spline terms. The relationships between the lifestyle score and the outcomes of interest were approximately linear.