Consonni D, Bertazzi P A, Zocchetti C
Istituti Clinici di Perfezionamento, Clinica del Lavoro L Devoto, Milan, Italy.
Occup Environ Med. 1997 Nov;54(11):772-6. doi: 10.1136/oem.54.11.772.
In occupational epidemiology, the need to consider the age factor properly influences the choice of study design and analytical techniques. In most studies, age is viewed as a potential confounder. Age is strongly associated with end points of interest in occupational epidemiology (diseases, physiological characteristics, doses of xenobiotics, etc), but to measure age as a confounder it must be associated with the exposure under study. When the exposure of interest is time related-for example, duration of employment, time since first exposure, cumulative exposure-a strong intrinsic association with age can be anticipated, and age will behave as a (usually strong) confounder. When occupational exposures without a direct relation with age-for example, job, department, type of exposure-are evaluated, the degree and direction of confounding bias cannot be anticipated. Control of the confounding effect of age can be accomplished in the design phase of a study by way of randomisation, restriction, and matching. Randomisation is seldom viable in occupational settings. Restriction is rarely used in the case of age. Matching is often used in a case-control study as a method to increase the study efficiency, but it must be followed by proper matched or stratified analysis. Options for age adjustment in the analysis phase involve stratification and regression methods. In longitudinal studies the modified life table analysis is used to take into account the fact that subjects cross categories of age as the study proceeds. Stability of relative measures of effect over age strata favoured the greater use of relative risks than risk differences. In the presence of effect modification the influence of age should not be eliminated; its interaction with exposure should be explicitly considered.
在职业流行病学中，正确考虑年龄因素的必要性会影响研究设计和分析技术的选择。在大多数研究中，年龄被视为一个潜在的混杂因素。年龄与职业流行病学中感兴趣的终点（疾病、生理特征、外源性物质剂量等）密切相关，但要将年龄作为混杂因素来衡量，它必须与所研究的暴露相关。当感兴趣的暴露与时间相关时，例如就业持续时间、首次暴露后的时间、累积暴露，可以预期与年龄有很强的内在关联，并且年龄将表现为一个（通常很强的）混杂因素。当评估与年龄无直接关系的职业暴露时，例如工作、部门、暴露类型，混杂偏倚的程度和方向无法预测。在研究的设计阶段，可以通过随机化、限制和匹配来控制年龄的混杂效应。随机化在职业环境中很少可行。在年龄方面很少使用限制。匹配在病例对照研究中经常被用作提高研究效率的方法，但必须随后进行适当的匹配或分层分析。分析阶段年龄调整的选项包括分层和回归方法。在纵向研究中，使用修正的生命表分析来考虑随着研究进行受试者跨越年龄类别的事实。效应相对测量在年龄层中的稳定性有利于更多地使用相对风险而非风险差异。在存在效应修饰的情况下，不应消除年龄的影响；应明确考虑其与暴露的相互作用。
