Publication bias in the environmental tobacco smoke/coronary heart disease epidemiologic literature

Abstract

Two approaches are used to assess publication bias in the environmental tobacco smoke/coronary heart disease (ETS/CHD) literature: (1) Statistical tests applied to all sex-specific relative risk (rr) estimates from 14 previously published studies indicate that publication bias is likely. A funnel graph of the studies' log relative risks plotted against their standard errors is asymmetrical, and weighted regression of the studies' log relative risks on their standard errors is significant (P < 0.01). (2) Previously unpublished ETS/CHD relative risks from the American Cancer Society's Cancer Prevention Studies (CPS-I and CPS-II) and the National Mortality Followback Survey (NMFS) do not show an increased CHD risk associated with ETS exposure. CPS-I: men, rr = 0.97 (0.90-1.05); CPS-I: women, rr = 1.03 (0.98-1.08); CPS-II: men, rr = 0.97 (0.87-1.08); CPS-II: women, rr = 1.00, (0.88-1.14); NMFS: men, rr = 0.97 (0.73-1.28); women, rr = 0.99 (0.84-1.16). Comparison of pooled relative risk estimates from 14 previously published studies (rr = 1.29; 1.18-1.41) and unpublished results from three studies (rr = 1.00; 0.97-1.04) also indicates that published data overestimate the association of spousal smoking and CHD (chi 2 = 25.1; P < 0.0001).