Waterpipe plus some occasions to smoke a cigarette per week | Person-years | Case (n = 67) | Crude HR (95%CI) | p for trend | Adjusted HR (95%CI) a | p for trend |
---|---|---|---|---|---|---|
Age at starting smoking (years, missing 6 cases) | ||||||
 Never smoker | 215,223.6 | 35 | 1.00 |  | 1.00 |  |
 26–42 | 26,559.5 | 15 | 3.45 (1.88–6.32) |  | 3.49 (1.64–7.44) |  |
 15–25 | 27,559.8 | 11 | 2.45 (1.24–4.83) |  < 0.001 | 2.81 (1.24–6.36) | 0.001 |
Frequency (session per day) | ||||||
 Never smoker | 215,223.6 | 35 | 1.00 |  | 1.00 |  |
 One per week-10 per day | 40,835.7 | 24 | 3.63 (2.16–6.10) |  | 2.96 (1.55–5.62) |  |
 11–75 per day | 20,866.4 | 8 | 2.30 (1.07–4.97) |  < 0.001 | 1.87 (0.79–4.41) | 0.029 |
Duration of smoking (years, missing one case) | ||||||
 Never smoker | 215,223.6 | 35 | 1.00 |  | 1.00 |  |
 1–20 | 41,727.6 | 14 | 2.06 (1.11–3.83) |  | 2.20 (1.05–4.62) |  |
 21–70 | 18,526.2 | 17 | 5.55 (3.11–9.90) |  < 0.001 | 3.04 (1.51–6.09) | 0.001 |
Cumulative frequency (times, missing one case) | ||||||
 Never smoker | 215,223.6 | 35 | 1.00 |  | 1.00 |  |
 1–150 | 30,581.4 | 13 | 2.63 (1.39–4.97) |  | 2.65 (1.26–5.60) |  |
 156–3,250 | 28,693.2 | 18 | 3.79 (2.15–6.70) |  < 0.001 | 2.69 (1.36–5.33) | 0.004 |