Nevertheless, classification of lifetime abstainers is indeed a difficult task and, when carefully measured at more than one point in time, a substantial fraction of “lifetime abstainers” reported alcohol consumption at other different time points [138]. But those who were drinkers of small quantities on rare occasions would not bias the results of the comparison group since there is no plausible biological pathway for an effect of such drinking [139]. The best comparison group for alcohol epidemiology with respect to chronic disease outcomes would thus be a combination of lifetime abstainers with those who never consumed alcohol in quantities which could have a biological impact [138].
