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Table 3 Sensitivity and subgroup analysis for SSRI use and breast cancer mortality

From: Selective serotonin reuptake inhibitor use and breast cancer survival: a population-based cohort study

  Non-usersa Users Unadjusted HR (95% CI) Adjusted HRb (95% CI)
n Person-years Deathsc n Person-years Deaths
Main analysis 18,885 105,433 2539 4784 20,722 514 1.17 (1.07, 1.29) 1.27 (1.16, 1.40)
Death definition
 All-cause 18,885 105,433 4358 4784 20,722 933 1.16 (1.08, 1.25) 1.33 (1.23, 1.43)
 Primary or secondary breast cancer cause 18,885 105,433 2965 4784 20,722 593 1.16 (1.06, 1.27) 1.28 (1.17, 1.40)
Exposure definition
 Year before diagnosis 21,768 138,969 2810 1901 10,855 243 1.09 (0.96, 1.24) 1.18 (1.03, 1.34)
 Year after diagnosis 20,999 113,219 2700 2670 12,935 353 1.11 (1.00, 1.25) 1.23 (1.10, 1.38)
Exposure lag
 6 months 18,541 114,762 2455 5128 23,195 598 1.25 (1.14, 1.36) 1.36 (1.24, 1.49)
 2 years 19,635 87,457 1912 4034 16,319 360 1.14 (1.02, 1.28) 1.22 (1.09, 1.37)
Prior antidepressant medicationd 1769 9316 258 2019 8861 241 1.11 (0.93, 1.33) 1.21 (1.00, 1.45)
SSRI vs other antidepressant medication 3791 17,390 435 4784 20,722 514 1.02 (0.89, 1.15) 1.06 (0.93, 1.20)
Tamoxifen use
 Non-user 11,110 52,864 1674 2790 10,678 341 1.16 (1.03, 1.30) 1.25 (1.11, 1.41)
 User 7775 52,569 865 1994 10,044 173 1.13 (0.96, 1.34) 1.36 (1.15, 1.61)
 Adherant usere 3612 26,159 489 882 4645 86 1.10 (0.87, 1.38) 1.30 (1.03, 1.65)
Adjustment
 Excluding ‘previous hot flush’ diagnosisf 18,885 105,433 2539 4784 20,722 514 1.17 (1.07, 1.29) 1.24 (1.12, 1.36)
 CC lifestyleg 12,568 70,673 1561 3290 14,116 327 1.18 (1.05, 1.33) 1.24 (1.10, 1.40)
 MI lifestyle 18,885 105,433 2539 4784 20,722 514 1.17 (1.07, 1.29) 1.26 (1.14, 1.38)
 CC diagnosish 7388 40,419 813 1863 7980 164 1.13 (0.95, 1.34) 1.14 (0.96, 1.35)
 MI diagnosis 18,885 105,433 2539 4784 20,722 514 1.17 (1.07, 1.29) 1.27 (1.14, 1.40)
  1. HR hazard ratio, CI confidence interval, SSRI selective serotonin reuptake inhibitor
  2. aExcept for ‘SSRI vs other anti-hypertensive medication’ where patients who received a different anti-hypertensive medication serve as the reference group
  3. bAdjusted for age, deprivation, year of diagnosis, cancer treatment within 6 months (radiotherapy, chemotherapy, surgery, tamoxifen, aromatase inhibitors), comorbidities (cerebrovascular disease, chronic pulmonary disease, congestive heart disease, diabetes, liver disease, myocardial infarction, peptic ulcer disease, peripheral vascular disease, renal disease), hot flushes and pre-diagnosis use of hormone replacement therapy or oral contraceptives
  4. cDeaths with a primary cause of breast cancer unless otherwise stated
  5. dSSRI users vs non-users, restricted to patients with an antidepressant prescription in the year prior to cancer diagnosis
  6. eDefined as having been prescribed at least 150 defined daily doses of tamoxifen in the first six months after cancer diagnosis
  7. fNot adjusting for a previous hot flush diagnosis
  8. gComplete case (CC), additionally adjusted for smoking, obesity and alcohol consumption
  9. hMultiply imputed (MI), additionally adjusted for stage and grade