Table 3 Mixed smoking of both waterpipe and cigarettes and the risk of gastric cancer mortality in Northern Vietnam among 25,619 participants for over 12 years-following-up, 2008–2019

 Never smoker

215,223.6

35

1.00

1.00

 26–42

38,618.8

18

2.88 (1.63–5.10)

2.88 (1.38–5.99)

 15–25

44,017.9

16

2.27 (1.26–4.11)

 < 0.001

2.71 (1.27–5.78)

0.003

Frequency (session per day, missing 2 case)

 Never smoker

215,223.6

35

1.00

1.00

 One per week-10 per day

52,706.7

25

2.98 (1.78–4.98)

2.54 (1.33–4.84)

 11–100 per day

42,203.1

18

2.62 (1.48–4.62)

 < 0.001

2.31 (1.16–4.61)

0.014

Duration of smoking (years, missing 23 cases)

 Never smoker

215,223.6

35

1.00

1.00

 1–15

30,682.6

8

1.64 (0.76–3.55)

2.18 (0.90–5.29)

 16–65

28,977.9

14

3.01 (1.62–5.59)

 < 0.001

2.35 (1.10–5.04)

0.025

Cumulative smoking frequency (times, missing 3 cases)

 Never smoker

215,223.6

35

1.00

1.00

 1–164

45,557.0

17

2.34 (1.31–4.18)

2.47 (1.22–4.99)

 165–3,250

46,037.7

25

3.34 (2.00–5.59)

 < 0.001

2.60 (1.36–4.96)

0.004