Am J Epidemiol. 2014 Feb 1;179(3):299-302. doi: 10.1093/aje/kwt274. Epub 2013 Dec 18.
Cumulative exposure--the product of intensity and duration for a constant exposure rate or its integral over time if variable--has been widely used in epidemiologic analyses of extended exposures, for example, the "pack-years" variable for tobacco smoking. Although the effects of intensity and duration are known to differ for exposures like smoking and ionizing radiation and simple cumulative exposure does not explicitly allow for modification by other time-related variables, such as age at exposure or time since exposure, the cumulative exposure variable has the merit of simplicity and has been shown to be one of the best predictors for many exposure-response relationships. This commentary discusses recent refinements of the pack-years variable, as discussed in this issue of the Journal by Vlaanderen et al. (Am J Epidemiol. 2014;179(3):290-298), in the broader context of general exposure-time-response relationships.
累积暴露量——在恒定暴露率下，强度和持续时间的乘积，或者在暴露率随时间变化的情况下的积分——在扩展暴露的流行病学分析中得到了广泛应用，例如吸烟的“包年”变量。尽管已知吸烟和电离辐射等暴露的强度和持续时间的影响不同，并且简单的累积暴露量不能明确允许其他与时间相关的变量（例如暴露时的年龄或暴露后的时间）进行修正，但累积暴露量变量具有简单的优点，并且已经被证明是许多暴露-反应关系的最佳预测因子之一。本评论在更广泛的一般暴露-时间-反应关系背景下，讨论了本期杂志中 Vlaanderen 等人讨论的“包年”变量的最新改进（Am J Epidemiol. 2014;179(3):290-298）。
