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Table 4 Relative risk of breast cancer in relation to ever smoking, by level of alcohol consumption

From: Smoking and risk of breast cancer in the Generations Study cohort

Strata Total number of cases in strata HR for ever smoking relative to never smoking within strata of alcohol consumptiona 95% CI P value
Alcoholb
 Non-drinker 110 0.97 0.61–1.52 0.89
 Ever drinker 1705 1.18 1.07–1.30 0.0010
   Interaction P c = 0.41
Alcoholb
 Non-drinker 110 0.97 0.61–1.52 0.89
  < 20 g/day 706 1.17 1.00–1.36 0.049
 20 to < 40 g/day 356 1.17 0.95–1.44 0.13
 40 to < 60 g/day 87 1.12 0.73–1.72 0.61
  ≥ 60 g/day 27 1.92 0.78–4.76 0.16
 Current, amount unknown 180 1.47 1.09–1.98 0.011
 Former drinker 295 0.98 0.78–1.25 0.89
 Drinker, details missing 54 0.73 0.38–1.42 0.35
   Interaction P c = 0.33
  1. aAdjusted for attained age (Cox regression time scale); time since recruitment to cohort (0, 1–2, 3+ years); birth cohort (1908–1939, 1940–1949, 1950–1959, 1960–1969, 1970–1996); benign breast disease (yes/no); family history of breast cancer in first-degree relatives (yes/no); socio-economic score (Acorn score as trend, missing); age at menarche (trend, missing); age at first pregnancy (trend, missing); parity (trend, missing); duration of breastfeeding (trend, missing); current oral contraceptive use before menopause (yes/no); physical activity [log(metabolic equivalent) trend, missing]; pre-menopausal body mass index at age 20 years (trend, missing); post-menopausal body mass index (trend, missing); menopausal hormone therapy use (never used, ex-user, current oestrogen-only user, current oestrogen plus progestogen user, current user of other types, missing); menopausal status (pre- or post-menopausal) and age at menopause (trend, missing)
  2. bTime updated through follow-up period
  3. cInteraction across all categories, including missing groups