Hughes John R, Callas Peter W
Department of Psychiatry, University of Vermont, Burlington, VT 05401, USA.
Nicotine Tob Res. 2006 Feb;8(1):7-12. doi: 10.1080/14622200500431635.
Articles on smoking cessation often present curves representing the percentage of smokers still abstinent over time. The purpose of this paper is to illustrate how common conclusions from inspecting these curves may be misleading because they are based on assumptions of which readers are not aware. For example, when active and control abstinence curves converge, this is often interpreted to indicate a diminution of treatment effect size over time. We use illustrative data to show that this interpretation is correct if one assumes a treatment has a constant additive effect; however, if one assumes treatment has a constant multiplicative effect, then converging curves can still indicate a constant treatment effect. Converging abstinence curves are also often interpreted to indicate that the rate of relapse is greater in the active than the control group. We illustrate that this interpretation is correct if one is interested in cumulative relapse rate and uses all subjects in the denominator; however, if one is interested in relapse over a discrete subperiod of time (e.g., immediately after treatment stops), and thus uses only those at risk for relapse, then converging curves can still indicate a constant relapse rate. When trials interpret abstinence curves, they should make clear whether they are assuming additive or multiplicative effects of treatment and are discussing overall or local relapse rates. They should also report both additive and multiplicative effect sizes.
关于戒烟的文章常常呈现出代表随着时间推移仍保持戒烟状态的吸烟者百分比的曲线。本文的目的是说明，通过审视这些曲线得出的常见结论可能具有误导性，因为它们基于读者未意识到的假设。例如，当主动戒烟组和对照组的戒烟曲线趋于一致时，这通常被解释为表明治疗效果大小随时间减小。我们用示例数据表明，如果假设治疗具有恒定的相加效应，那么这种解释是正确的；然而，如果假设治疗具有恒定的相乘效应，那么曲线趋同仍可表明治疗效果恒定。趋同的戒烟曲线也常常被解释为表明主动戒烟组的复发率高于对照组。我们说明，如果关注累积复发率并将所有受试者作为分母，那么这种解释是正确的；然而，如果关注在一个离散的子时间段（例如，治疗刚结束后）内的复发情况，从而仅将有复发风险的人作为分母，那么曲线趋同仍可表明复发率恒定。当试验解读戒烟曲线时，应明确他们是假设治疗的相加效应还是相乘效应，以及讨论的是总体复发率还是局部复发率。他们还应报告相加效应大小和相乘效应大小。
