Table 3.

Multivariable HR (95% CI) of colorectal adenomas by site according to quartile of heme iron intake

Colorectal adenomas (n = 1,409)Colon adenomasRectal adenomasa (n = 258)
Totala (n = 1,035)Proximalb (n = 344)Distalb (n = 642)
CasesHRc (95% CI)HRd (95% CI)CasesHRd (95% CI)CasesHRd (95% CI)CasesHRd (95% CI)CasesHRd (95% CI)
Total heme iron (mg/day)
 <0.753091.001.002201.00751.001301.00631.00
 0.75–<1.073511.16 (1.00–1.36)1.17 (1.00–1.36)2531.20 (1.00–1.45)831.18 (0.86–1.62)1581.25 (0.98–1.58)640.99 (0.69–1.42)
 1.07–<1.453821.28 (1.11–1.49)1.31 (1.11–1.54)2931.47 (1.21–1.78)1041.57 (1.13–2.18)1811.49 (1.16–1.90)640.96 (0.66–1.41)
 ≥1.453671.31 (1.13–1.53)1.36 (1.13–1.65)2691.49 (1.19–1.87)821.40 (0.94–2.07)1731.55 (1.16–2.07)671.05 (0.67–1.62)
Ptrend0.00030.0010.00030.060.0030.86
Nonnitrosylated heme iron (mg/day)
 <0.633061.001.002201.00781.001291.00621.00
 0.63–<0.923571.19 (1.02–1.39)1.17 (1.00–1.37)2591.20 (1.00–1.44)841.09 (0.79–1.49)1621.27 (1.00–1.61)620.97 (0.67–1.39)
 0.92–<1.243851.29 (1.11–1.50)1.27 (1.08–1.50)2871.37 (1.13–1.66)1031.34 (0.97–1.86)1751.42 (1.10–1.82)721.09 (0.75–1.58)
 ≥1.243611.27 (1.09–1.48)1.26 (1.04–1.53)2691.38 (1.10–1.72)791.09 (0.74–1.62)1761.53 (1.15–2.03)620.95 (0.61–1.47)
Ptrend0.0020.020.0050.540.0040.90
Nitrosylated heme iron (mg/day)
 <0.063371.001.002381.00751.001501.00671.00
 0.06–<0.133381.04 (0.89–1.21)1.02 (0.87–1.19)2551.09 (0.91–1.30)851.22 (0.89–1.67)1561.02 (0.81–1.28)590.88 (0.62–1.25)
 0.13–<0.233621.16 (1.00–1.35)1.11 (0.95–1.29)2671.16 (0.96–1.39)931.41 (1.02–1.93)1621.05 (0.83–1.32)701.06 (0.74–1.50)
 ≥0.233721.25 (1.08–1.45)1.18 (1.00–1.39)2751.24 (1.02–1.51)911.52 (1.08–2.15)1741.13 (0.88–1.44)620.94 (0.64–1.40)
Ptrend0.0010.030.030.020.320.97
  • aPhomogeneity colon vs. rectum = 0.16, 0.17, and 0.34 for total heme iron, non-nitrosylated heme iron, and nitrosylated heme iron, respectively.

  • bPhomogeneity proximal vs. distal = 0.68, 0.24, and 0.19 for total heme iron, non-nitrosylated heme iron, and nitrosylated heme iron, respectively.

  • cCox proportional hazards model with individuals' ages as the time scale.

  • dCox proportional hazards model with individuals' ages as the time scale and adjusted by colorectal cancer in first-degree relatives, educational level, smoking status, menopausal status, physical activity, BMI, total energy, intake of alcohol, fibers, dietary and supplemental calcium, and dietary zinc. Nitrosylated and non-nitrosylated heme iron were simultaneously included in the model.