Hazard ratios (HRs) for risk of stroke in men and women by serum cotinine or active smoking level
| Non-smokers (serum cotinine ng/ml) (n=4405)* | Smokers (n=228) | Non-smokers | |||||
| ≤0.05 | 0.06–0.19 | 0.20–0.70 | 0.71–15 | 1–9 Cigarettes /day | Cotinine ≤15 ng/ml† | p(trend)† | |
| All participants | |||||||
| Mean cotinine (ng/ml) | 0.05 | 0.14 | 0.34 | 1.70 | 100.01 | 0.15 | |
| Number of participants | 1858 | 1031 | 975 | 541 | 228 | 4405 | |
| Number of events | 80 | 34 | 32 | 19 | 11 | 165 | |
| Person-years | 13990 | 7901 | 7593 | 4182 | 1602 | 33666 | |
| Stroke rates/1000 | 5.72 | 4.30 | 4.21 | 4.54 | 6.87 | 4.90 | |
| HR (95% CI) | |||||||
| Model 1 | 1.00 | 0.78 (0.52 to 1.17) | 0.73 (0.48 to 1.10) | 0.74 (0.44 to 1.23) | 1.13 (0.60 to 2.13) | 0.91 (0.83 to 1.01) | 0.051 |
| Model 2 | 1.00 | 0.81 (0.54 to 1.22) | 0.75 (0.50 to 1.15) | 0.69 (0.41 to 1.16) | 1.03 (0.52 to 2.04) | 0.91 (0.83 to 1.00) | 0.051 |
| Model 3 | 1.00 | 0.82 (0.55 to 1.23) | 0.74 (0.48 to 1.13) | 0.69 (0.41 to 1.17) | 1.03 (0.52 to 2.04) | 0.91 (0.82 to 1.01) | 0.065 |
| Excluding former smokers | (n=2232) | (n=228) | |||||
| Mean cotinine (ng/ml) | 0.05 | 0.14 | 0.33 | 1.74 | 100.01 | 0.13 | |
| Number of participants | 1036 | 550 | 441 | 205 | 230 | 2232 | |
| Number of events | 37 | 17 | 10 | 6 | 11 | 70 | |
| Person-years | 7717 | 4162 | 3401 | 1550 | 1615 | 16830 | |
| Stroke rates/1000 | 4.79 | 4.08 | 2.94 | 3.87 | 6.81 | 4.16 | |
| HR (95% CI) | |||||||
| Model 1 | 1.00 | 0.87 (0.49 to 1.55) | 0.62 (0.30 to 1.26) | 0.86 (0.36 to 2.07) | 1.07 (0.53 to 2.15) | 0.95 (0.81 to 1.11) | 0.526 |
| Model 2 | 1.00 | 0.90 (0.50 to 1.62) | 0.60 (0.29 to 1.22) | 0.78 (0.32 to 1.89) | 1.12 (0.50 to 2.47) | 0.94 (0.80 to 1.10) | 0.407 |
| Model 3 | 1.00 | 0.91 (0.50 to 1.62) | 0.61 (0.30 to 1.26) | 0.81 (0.33 to 1.99) | 1.21 (0.55 to 2.65) | 0.94 (0.80 to 1.11) | 0.476 |
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↵* HRs for non-smokers from models with cotinine ≤0.05 as baseline. HRs for smokers from models comparing cotinine ≤0.05 with smokers of 1–9 cigarettes/day. Participants with pre-existing myocardial infarction or stroke are excluded.
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↵† From Cox regression models of log2(cotinine) level (representing a doubling in cotinine) and stroke in non-smokers, cotinine ≤15 ng/ml.
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Model 1 = age+gender+region; Model 2 = model 1+BMI+SBP+DBP+total cholesterol+HDLc+triglycerides+FEV1+CRP+IL-6+white cell count; Model 3 = model 2+pre-existing diabetes+physical activity (inactive or active)+alcohol intake (none/occasional, light, heavy)+smoking history (never/ time since quitting)+social class (non-manual, manual and armed forces).
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CHD, coronary heart disease; CRP, C-reactive protein; FEV1, forced expiratory volume in 1 s; HDLc, high-density lipoprotein cholesterol; IL, interleukin.
