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Table 2 Multivariate a adjusted hazard ratio (HR) estimates for rectal cancer with 95% confidence intervals (CI) among women (n = 302,866) and men (n = 299,376) according to various measures of smoking exposure at enrollment, compared with never smokers

From: Smoking increases rectal cancer risk to the same extent in women as in men: results from a Norwegian cohort study

  Men Women
  Cases n = 1,336 Person-years HR 95% CI Cases n = 840 Person-years HR 95% CI
Smoking status         
Never 298/98,388 1,369,691 1.00 Ref. 350/123,503 1,744,944 1.00 Ref.
Former 433/78,662 1,138,881 1.28 1.11-1.50 169/64,021 824,913 1.26 1.05-1.52
Current 605/122,326 1,913,477 1.26 1.09-1.45 321/115,342 1,621,343 1.29 1.10-1.51
Ptrend b     <0.05     <0.05
Ever 1,038/200,988 3,052,358 1.27 1.11-1.45 490/179,363 2,446,256 1.28 1.11-1.48
Ever smokersc         
Age at smoking initiation in years         
≥25 116/16,415 268,600 1.23 0.99-1.52 99/23,150 357,101 1.19 0.95-1.49
20-24 211/38,540 592,480 1.35 1.13-1.61 136/40,824 588,736 1.45 1.18-1.78
≤19 362/96,856 1,294,339 1.28 1.08 − 1.50 142/80,620 928,955 1.35 1.10-1.67
Ptrend b     <0.05     <0.05
Number of cigarettes smoked per day         
1-9 207/39,218 604,421 1.07 0.90-1.29 169/59,570 824,198 1.15 0.96-1.39
10-19 524/99,761 1,526,804 1.35 1.17-1.56 255/93,002 1,268,980 1.37 1.16-1.62
≥20 259/56,319 832,845 1.31 1.11-1.55 64/25,270 337,874 1.38 1.05-1.81
Ptrend b     <0.0001     <0.0001
Smoking duration in years         
1-19 326/80,190 1,250,222 1.21 1.03-1.42 220/87,999 1,263,528 1.17 0.99 − 1.40
20-29 457/97,685 1,471,526 1.29 1.11-1.50 222/81,713 1,089,772 1.37 1.15-1.64
≥30 232/21,144 299,518 1.31 1.09-1.59 48/7,918 76,398 1.54 1.11-2.12
Ptrend b     <0.05     <0.0001
Number of pack-years smokedd         
0-9 298/68,003 943,796 1.17 0.99-1.37 241/88,884 1,270,193 1.21 1.02-1.42
10-19 385/74,235 1,014,305 1.33 1.14-1.54 178/64,544 862,029 1.38 1.14-1.66
≥20 302/52,392 647,100 1.35 1.14-1.58 69/23,263 288,147 1.47 1.13-1.91
Ptrend b     <0.0001     <0.0001
  1. aAdjusted for age, body mass index, level of physical activity all at enrollment and duration of education. bNever smokers included in the model. cTotal numbers of ever smokers do not equal the total in different smoking exposures due to missing values in different smoking exposures groups. dPack-years were calculated as numbers of cigarettes smoked per day, divided by 20 and multiplied by the number of years smoked.
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