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Mortality by β-carotene (BC) supplementation: participants who initiated smoking at ≥21 years and smoked ≥21 cigarettes/d (Alpha-Tocopherol Beta-Carotene Study 1985–1993). The Kaplan–Meier survival curves for the BC and placebo arms are shown. Each step indicates one death. (a) Mortality after randomisation. For the difference between the two curves, P = 0·024. (b) Mortality by follow-up age.
