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

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 smokers^c

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 smoked^d

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