Table 3.

Associations of oophorectomy with incident CKD defined by adjudicated diagnostic codes (secondary analyses)

Chronic Condition and StrataBilateral OophorectomyReferent WomenUnadjusted ModelsAdjusted Modelsa
N at RiskPerson-yrN of EventsAbsolute Risk, % (95% CI)bN at RiskPerson-yrN of EventsAbsolute Risk, % (95% CI)bHazard Ratio (95% CI)P ValueHazard Ratio (95% CI)P Value
Secondary analyses
 Overall164223,467615.3 (3.8 to 7.3)164723,530434.7 (3.3 to 6.6)1.44 (0.98 to 2.12)0.061.17 (0.79 to 1.74)0.44
 Age ≤45 yr102414,754395.8 (3.9 to 8.6)102814,542264.4 (2.8 to 6.9)1.50 (0.92 to 2.44)0.101.20 (0.73 to 1.99)0.48
  ET>45 yrc6448086225.8 (3.3 to 9.8)6007459197.8 (4.6 to 13.3)1.07 (0.58 to 1.97)0.840.97 (0.52 to 1.81)0.92
  No ET or ≤451761639925.1 (10.7 to 52.3)161164423.4 (0.9 to 12.2)4.70 (0.99 to 22.31)0.052.08 (0.39 to 11.10)0.39
 Age 46–49 yr6188713224.7 (2.8 to 7.7)6198988175.2 (3.0 to 8.9)1.34 (0.71 to 2.53)0.361.23 (0.64 to 2.35)0.54
  ET>49 yrd4465959145.4 (2.7 to 10.5)4255855144.1 (2.3 to 7.1)1.00 (0.47 to 2.10)0.990.83 (0.39 to 1.78)0.63
  No ET or ≤49 yr155148952.6 (0.9 to 7.2)154159934.4 (0.7 to 24.5)1.80 (0.46 to 6.99)0.401.20 (0.30 to 4.74)0.80
Sensitivity analysese
 Overall65610,113224.2 (2.5 to 6.9)88813,004193.7 (2.3 to 6.1)1.37 (0.74 to 2.56)0.311.25 (0.67 to 2.32)0.48
 Age ≤45 yr4206565144.5 (2.4 to 8.5)5928572112.7 (1.4 to 5.2)1.50 (0.68 to 3.30)0.311.32 (0.60 to 2.94)0.49
 Age 46–49 yr236354883.6 (1.6 to 7.9)296443286.0 (2.9 to 12.5)1.15 (0.42 to 3.14)0.781.11 (0.41 to 3.03)0.84
  • 95% CI, 95% confidence interval; ET, estrogen therapy.

  • a Hazard ratios were calculated using Cox proportional hazards models with age as the timescale and adjusted using inverse probability weights derived from a regression model including 17 chronic conditions present at baseline, years of education (unknown, ≤12, 13–16, or >16), race (white versus nonwhite), body mass index (unknown or <30 versus ≥30 kg/m2), cigarette smoking (current or former versus never), age at baseline (continuous), and calendar year at baseline (continuous). These adjustments were performed separately in each stratum to maximize the balance at baseline. None of the interactions by age were significant.

  • b Absolute cumulative risk at 20 years after bilateral oophorectomy (or index) calculated using the Kaplan–Meier method. The estimates were adjusted using inverse probability weights derived from a logistic regression model including 17 chronic conditions present at baseline, years of education (unknown, ≤12, 13–16, or >16), race (white versus nonwhite), body mass index (unknown or <30 versus ≥30 kg/m2), cigarette smoking (current or former versus never), age at baseline (continuous), and calendar year at baseline (continuous). These adjustments were performed separately in each stratum to maximize the balance at baseline.

  • c Women who were taking ET on their 46th birthday after bilateral oophorectomy (only oral or transdermal). Women who developed CKD before their 46th birthday, died or were lost to follow-up before their 46th birthday, or had not reached age 46 years old as of December 31, 2014 were not included in the corresponding analysis. Follow-up for these analyses was started at age 46 years old. None of the interactions by ET were significant in the ≤45-years-old age stratum.

  • d Women who were taking ET on their 50th birthday after bilateral oophorectomy (only oral or transdermal). Women who developed CKD before their 50th birthday, died or were lost to follow-up before their 50th birthday, or had not reached age 50 years old as of December 31, 2014 were not included in the corresponding analysis. Follow-up for these analyses was started at age 50 years old. None of the interactions by ET were significant in the 46- to 49-years-old age stratum.

  • e Excluding women with any of the 17 chronic conditions at index date or with onset of CKD defined by eGFR or adjudicated diagnostic codes before the index date.