Table 5 Cigarettes plus some occasions to smoke a waterpipe and the risk of gastric cancer mortality in Northern Vietnam among 22,471 participants for over 12 years following-up, 2008–2019

Age at starting smoking (years, missing 7 cases)

 Never smoker

215,223.6

35

1.00

1.00

 26–40

24,250.4

7

1.80 (0.80–4.06)

1.91 (0.74–4.95)

 15–25

26,969.3

8

1.88 (0.87–4.05)

0.047

2.34 (0.93–5.91)

0.058

Frequency (cigarette per day, missing one case)

 Never smoker

215,223.6

35

1.00

1.00

 One per week-6 per day

30,613.6

8

1.63 (0.76–3.53)

1.63 (0.67–3.94)

 7–80 per day

30,365.2

13

2.70 (1.43–5.11)

0.002

2.51 (1.16–5.43)

0.019

Duration of smoking (years)

 Never smoker

215,223.6

35

1.00

1.00

 1–15

33,150.4

9

1.71 (0.82–3.56)

2.15 (0.91–5.07)

 16–65

26,510.1

13

3.06 (1.62–5.78)

 < 0.001

2.38 (1.10–5.18)

0.024

Cumulative frequency (times, missing one case)

 Never smoker

215,223.6

35

1.00

1.00

 1–100

33,129.1

10

1.90 (0.94–3.83)

2.19 (0.95–5.02)

 104–2,800

25,351.6

11

2.72 (1.38–5.36)

0.002

2.31 (1.03–5.17)

0.032