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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

From: Testing the proportional hazards assumption in case-cohort analysis

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
  1. Note: Abbreviation: Mets metabolic equivalent tasks per hour per week, NSAID use of nonsteroidal anti-inflammatory drugs in the preceding year.
  2. 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.