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Table 2 Exposure to human insulin and incidences of breast cancer and the adjusted hazard ratios comparing exposed to unexposed

From: Prolonged use of human insulin increases breast cancer risk in Taiwanese women with type 2 diabetes

Exposure to human insulin Case number Incident breast cancer % Person-years Incidence rate (per 100,000 person-years) Primary model Sensitivity model I Sensitivity model II
HR 95 % CI P HR 95 % CI P HR 95 % CI P
 Never-users 422235 4711 1.12 2190014.8 215.1 1.000    1.000    1.000   
 Ever-users 59798 559 0.93 268941.3 207.9 1.033 (0.936-1.139) 0.5200 0.994 (0.907-1.090) 0.9013 1.033 (0.936-1.139) 0.5200
Time since starting human insulin (months)           
 Never-users 422235 4711 1.12 2190014.8 215.1 1.000    1.000    1.000   
 <35 19409 165 0.85 88579.0 186.3 0.924 (0.787-1.085) 0.3358 0.877 (0.750-1.027) 0.1024 0.924 (0.787-1.085) 0.3358
 35-67 19817 173 0.87 89856.1 192.5 0.988 (0.843-1.158) 0.8813 0.944 (0.809-1.101) 0.4603 0.988 (0.843-1.158) 0.8813
 ≥67 20572 221 1.07 90506.3 244.2 1.185 (1.026-1.368) 0.0209 1.161 (1.011-1.333) 0.0342 1.185 (1.026-1.368) 0.0209
Cumulative dose of human insulin exposure (units)           
 Never-users 422235 4711 1.12 2190014.8 215.1 1.000    1.000    1.000   
 <4,000 19106 151 0.79 89076.3 169.5 0.872 (0.738-1.030) 0.1069 0.819 (0.695-0.965) 0.0169 0.982 (0.837-1.152) 0.8264
 4,000-39,000 20322 170 0.84 89166.3 190.7 0.960 (0.818-1.126) 0.6148 0.919 (0.787-1.073) 0.2863 1.184 (1.017-1.380) 0.0298
 ≥39,000 20370 238 1.17 90698.7 262.4 1.260 (1.096-1.450) 0.0012 1.239 (1.084-1.416) 0.0017 0.961 (0.828-1.115) 0.5987
Cumulative duration of human insulin exposure (months)          
 Never-users 422235 4711 1.12 2190014.8 215.1 1.000    1.000    1.000   
 <2.8 19751 151 0.76 90689.0 166.5 0.855 (0.724-1.009) 0.0643 0.809 (0.687-0.953) 0.0112 0.855 (0.724-1.009) 0.0643
 2.8-21.7 19716 167 0.85 87633.9 190.67 0.981 (0.834-1.153) 0.8142 0.927 (0.792-1.084) 0.3407 0.981 (0.834-1.153) 0.8142
 ≥21.8 20331 241 1.19 90618.4 266.0 1.257 (1.094-1.446) 0.0013 1.240 (1.085-1.416) 0.0015 1.257 (1.094-1.446) 0.0013
  1. HR: hazard ratio, CI: confidence interval
  2. Primary model: adjusted for all variables listed in Table 1.
  3. Sensitivity model I: adjusting only for important risk factors of breast cancer including age, diabetes duration, obesity, estrogen, metformin, statin and angiotensin converting enzyme inhibitor/angiotensin receptor blocker.
  4. Sensitivity model II: including human insulin exposure post entry date but prior to breast cancer diagnosis in the calculation of the dose–response parameters.
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