Table 2.

RRs (95% CIs) of colorectal, colon, and rectal cancer according to quintiles of heme iron intake of men and women in the NLCS (9.3 years of follow-up)

Men
Women
Q1Q2Q3Q4Q5PtrendContinuous*Q1Q2Q3Q4Q5PtrendContinuous*
Median heme intake (mg/d)0.600.871.081.341.850.470.710.921.131.54
Person-years3,7163,7673,7093,7793,71818,6884,0384,0283,9653,9914,01320,035
Colorectal cancer
    Cancer cases (n)167164190179169869119133149137128666
    Age-adjusted RR (95% CI)1 (Reference)0.99 (0.76-1.28)1.16 (0.90-1.49)1.08 (0.84-1.39)1.06 (0.82-1.37)0.461.07 (0.91-1.24)1 (Reference)1.12 (0.84-1.48)1.29 (0.98-1.70)1.16 (0.88-1.54)1.11 (0.83-1.47)0.460.96 (0.81-1.13)
    Multivariate RR (95% CI)1 (Reference)0.99 (0.75-1.29)1.13 (0.86-1.48)1.06 (0.80-1.39)1.16 (0.87-1.55)0.271.11 (0.93-1.33)1 (Reference)1.14 (0.84-1.54)1.39 (1.03-1.87)1.19 (0.87-1.62)1.22 (0.89-1.68)0.221.00 (0.83-1.21)
    >2 y RR§ (95% CI)1 (Reference)1.11 (0.83-1.49)1.20 (0.90-1.61)1.20 (0.89-1.62)1.32 (0.96-1.80)0.081.15 (0.95-1.39)1 (Reference)1.09 (0.78-1.51)1.47 (1.08-2.02)1.18 (0.85-1.65)1.20 (0.86-1.69)0.240.99 (0.81-1.20)
Colon cancer
    Cancer cases (n)108100109114108539841081089688484
    Age-adjusted RR (95% CI)1 (Reference)0.94 (0.69-1.27)1.03 (0.76-1.39)1.07 (0.80-1.45)1.06 (0.78-1.43)0.471.04 (0.86-1.25)1 (Reference)1.29 (0.94-1.77)1.32 (0.97-1.81)1.15 (0.84-1.59)1.08 (0.78-1.50)0.940.90 (0.74-1.09)
    Multivariate RR (95% CI)1 (Reference)0.98 (0.71-1.35)1.04 (0.75-1.44)1.13 (0.82-1.56)1.29 (0.92-1.81)0.101.16 (0.94-1.43)1 (Reference)1.31 (0.94-1.85)1.44 (1.02-2.01)1.18 (0.83-1.68)1.20 (0.83-1.74)0.560.96 (0.77-1.20)
    >2 y RR§ (95% CI)1 (Reference)1.08 (0.76-1.53)1.07 (0.75-1.53)1.29 (0.90-1.83)1.50 (1.03-2.17)0.021.22 (0.98-1.52)1 (Reference)1.26 (0.87-1.83)1.56 (1.09-2.23)1.26 (0.86-1.83)1.19 (0.80-1.77)0.430.97 (0.78-1.22)
Rectal cancer
    Cancer cases (n)59648266623333526414340185
    Age-adjusted RR (95% CI)1 (Reference)1.08 (0.74-1.58)1.41 (0.98-2.01)1.10 (0.76-1.60)1.08 (0.74-1.58)0.691.11 (0.89-1.39)1 (Reference)0.73 (0.43-1.23)1.15 (0.72-1.83)1.23 (0.77-1.95)1.17 (0.73-1.88)0.141.12 (0.88-1.43)
    Multivariate RR (95% CI)1 (Reference)1.00 (0.68-1.49)1.30 (0.89-1.90)0.97 (0.65-1.45)0.98 (0.64-1.50)0.841.04 (0.80-1.35)1 (Reference)0.72 (0.40-1.27)1.19 (0.72-1.98)1.27 (0.76-2.13)1.23 (0.73-2.07)0.111.12 (0.86-1.46)
    >2 y RR§ (95% CI)1 (Reference)1.17 (0.75-1.80)1.44 (0.95-2.19)1.10 (0.71-1.72)1.06 (0.66-1.71)0.941.04 (0.79-1.38)1 (Reference)0.69 (0.37-1.29)1.18 (0.68-2.05)1.07 (0.60-1.91)1.20 (0.68-2.12)0.251.05 (0.76-1.43)
  • * Per increment of 1 mg heme/d.

  • The no. colorectal cancer cases is lower than no. colon plus rectal cancer cases due to cases with tumors in both sites.

  • Adjusted for age at baseline (y), BMI (kg/m2), family history of colorectal cancer (yes, no), cigarette smoker (never, former, current), nonoccupational physical activity (<30, 30-60, 60-90, >90 min/d), total energy intake (kJ), consumption of alcohol (0-4.9, 5-14.9, 15-29.9, ≥30 g/d for men; 0, 0.1-4.9, 5-14.9, ≥15 g/d for women), and total vegetable consumption (g/d).

  • § Cases diagnosed during the first 2 years of follow-up were excluded.