Table 3.
Assessment of proportional hazards for each variable in the multivariate cox model for the example case-cohort study of colorectal cancer risk, using insulin levels as the primary exposure variable
| Covariates in the model | Corr with event time | Corr with rank of time | Corr with KM estimates |
|---|---|---|---|
| Insulin |
0.154 |
0.176 |
0.164 |
| Mets for physical activity: (0,3.75)-ref |
|
|
|
| (3.75,10) |
0.389 |
0.384 |
0.397 |
| (10,20) |
0.045 |
0.040 |
0.044 |
| > = 20 |
0.629 |
0.686 |
0.645 |
| Ethnic: white -ref |
|
|
|
| Black |
0.305 |
0.304 |
0.294 |
| Hispanic |
0.167 |
0.166 |
0.176 |
| Others |
0.820 |
0.586 |
0.704 |
| Family history of colorectal cancer |
0.628 |
0.598 |
0.624 |
| History of colonoscopy |
0.099 |
0.076 |
0.089 |
| Smoking: none-ref |
|
|
|
| Former |
0.962 |
0.858 |
0.887 |
| Current |
0.613 |
0.594 |
0.598 |
| Alcohol consumption: none-ref |
|
|
|
| (0,3) |
0.491 |
0.326 |
0.411 |
| > = 3 |
0.219 |
0.256 |
0.255 |
| NSAID |
0.059 |
0.105 |
0.075 |
| Age group continuous | 0.322 | 0.181 | 0.261 |
Note: Abbreviation: Mets metabolic equivalent tasks per hour per week, NSAID use of nonsteroidal anti-inflammatory drugs in the preceding year.
Multivariate Cox model was applied to the WHI case-cohort study with insulin as the primary exposure variable, categorized as quartile groups based on the distribution in the subcohort and then treated as a linear trend. The model included age group categorized as (a) 50 to 54 years of age (referent), (b) 55 to 59, (c) 60–64, (d) 65 to 69, (e) 70 to 74, (f) 75–79.