Table 2. Age- and multivariate-adjusted relative risks (95% CI) of suicide by smoking statusa.
| Men (HPFS, 1986–2008) | Women (NHS, 1976–2008) | Women (NHS II, 1989–2007) | Pooled resultsd | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
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| Smoking Variables | Cases/Pers.- years | Age-adjustedb | Multivariatec | Cases/Pers.-years | Age-adjustedb | Multivariatec | Cases/Pers.-years | Age-adjustedb | Multivariatec | Multivariatec |
| Smoking status | ||||||||||
| Never | 63/416,827 | 1.00 | 1.00 | 66/1,522,797 | 1.00 | 1.00 | 32/1,084,429 | 1.00 | 1.00 | 1.00 |
| Former smoker | 68/392,099 | 1.09 (0.77–1.54) | 1.09 (0.76–1.56) | 57/1,258,900 | 1.09 (0.77–1.56) | 1.18 (0.83–1.69) | 18/399–971 | 1.43 (0.80–2.55) | 1.21 (0.67–2.18) | 1.15 (0.91–1.45) |
| Current smoker | 34/61,462 | 4.38 (2.85–6.74) | 3.00 (1.90, 4.76) | 98/708,260 | 2.93 (2.13–4.03) | 2.70 (1.95–3.72) | 21/177,080 | 4.20 (2.42–7.30) | 2.24 (1.25–4.02) | 2.69 (2.11–3.42) |
| Cigarettes smoked per day (CPD) in current vs. never smokers | ||||||||||
| Never | 63/416,827 | 1.00 | 1.00 | 66/1,522,797 | 1.00 | 1.00 | 32/1,084,429 | 1.00 | 1.00 | 1.00 |
| 1–14 CPD | 9/16,712 | 4.43 (2.13–9.19) | 3.67 (1.70–7.91) | 21/205,058 | 2.25 (1.37–3.70) | 2.32 (1.41–3.82) | 6/63,594 | 3.44 (1.44–8.22) | 2.30 (0.94–5.64) | 2.59 (1.77–3.79) |
| 15–24 CPD | 8/17,744 | 3.31 (1.54–7.11) | 2.24 (0.99–5.06) | 25/270,509 | 1.92 (1.20–3.07) | 1.94 (1.20–3.11) | 6/60,413 | 3.76 (1.57–9.01 | 2.12 (0.85–5.25) | 2.03 (1.39–2.94) |
| ≥25 CPD | 12/17,386 | 6.47 (3.34–12.5) | 4.62 (2.19–9.74) | 45/195,980 | 4.71 (3.19–6.95) | 4.11 (2.74–6.14) | 5/27,270 | 7.07 (2.74–18.2) | 3.54 (1.31–9.57) | 4.13 (2.96–5.78) |
| Ptrend | <.001 | <.001 | <.001 | <.001 | <.001 | 0.006 | <.001 | |||
| Duration of smoking among former and current smokers | ||||||||||
| <10 years | 15/109,907 | 1.00 | 1.00 | 14/305,567 | 1.00 | 1.00 | 5/73,892 | 1.00 | 1.00 | 1.00 |
| 10–19 years | 10/100,018 | 0.71 (0.32–1.61) | 0.68 (0.29–1.57) | 32/432,833 | 1.55 (0.82–2.91) | 1.47 (0.78–2.76) | 12/293,143 | 0.60 (0.21–1.70) | 0.54 (0.19–1.53) | 0.89 (0.47–1.68) |
| ≥20 years | 63/215,211 | 2.06 (1.15–3.68) | 1.69 (0.92–3.12) | 105/1,173,711 | 1.90 (1.07–3.36) | 1.73 (0.97–3.08) | 19/197,263 | 1.14 (0.42–3.07) | 0.68 (0.25–1.87) | 1.45 (0.90–2.31) |
| Ptrend | 0.002 | 0.03 | 0.03 | 0.06 | 0.34 | 0.78 | 0.01 | |||
| Age started smoking among former and current smoker | ||||||||||
| ≥20 years | 11/23,274 | 1.00 | 1.00 | 36/281,251 | 1.00 | 1.00 | 7/49,414 | 1.00 | 1.00 | 1.00 |
| <20 years | 13/24,318 | 1.26 (0.52–3.05) | 1.94 (0.61–6.18) | 53/378,017 | 1.11 (0.72–1.71) | 1.18 (0.76–1.82) | 8/97,370 | 0.63 (0.23–1.74) | 0.49 (0.17–1.41) | 1.06 (0.58–1.95) |
| Years since quitting in former vs. never Smokers | ||||||||||
| Never | 63/416,653 | 1.00 | 1.00 | 66/1,522,797 | 1.00 | 1.00 | 32/1,084,429 | 1.00 | 1.00 | 1.00 |
| ≤5 years | 9/41,289 | 1.69 (0.83–3.43) | 1.59 (0.75–3.35) | 12/199,237 | 1.30 (0.70–2.40) | 1.48 (0.79–2.74) | 3/73,568 | 1.52 (0.46–4.97) | 1.08 (0.33–3.57) | 1.45 (0.93–2.26) |
| >5 years | 55/340,696 | 0.98 (0.68–1.42) | 1.05 (0.72–1.53) | 40/992,857 | 1.00 (0.67–1.48) | 1.13 (0.76–1.68) | 14/319,511 | 1.34 (0.71–2.52) | 1.21 (0.64–2.30) | 1.10 (0.86–1.42) |
| Ptrend | 0.30 | 0.46 | 0.58 | 0.39 | 0.77 | 0.27 | 0.62 | |||
Abbreviations: CI, confidence interval; CPD, cigarettes smoked per day; HPFS, Health Professionals Follow-up Study; NHS, Nurses' Health Study; RR, relative risk.
Cases of suicide were codes E950 to E959 according the Eight Revision InternationalClassification of Diseases (ICD).
Adjusted for age (continuous) and time interval.
Further adjusted for high alcohol consumption (≥30 g/d, yes or no), body-mass index (<25, 25–29.9, ≥30 kg/m2), physical activity (quintiles), cups of caffeinated coffee (continuous), marital status (married/partnership or widowed/separated/divorced/single), and reported regular use of minor tranquilizers (yes or no), and antidepressants (yes or no). For women of NHS2, multivariate model was further adjusted for hormonal status (post-menopausal without or with hormonal therapy, pre-menopausal or never used hormonal therapy).
Results from multivariate models were combined using random-effect model.