Purpose

Workers’ compensation claims consist of occupational injuries severe enough to meet a compensability threshold. Theoretically, systems with higher thresholds should have fewer claims but greater average severity. For research that relies on claims data, particularly cross-jurisdictional comparisons of compensation systems, this results in collider bias that can lead to spurious associations confounding analyses. In this study, I use real and simulated claims data to demonstrate collider bias and problems with methods used to account for it.

Methods

Using Australian claims data, I used a linear regression to test the association between claim rate and mean disability durations across Statistical Areas. Analyses were repeated with nesting by state/territory to account for variations in compensability thresholds across compensation systems. Both analyses are repeated on left-censored data. Simulated claims data are analysed with Cox survival analyses to illustrate how left-censoring can reverse effects.

Results

The claim rate within a Statistical Area was inversely associated with disability duration. However, this reversed when Statistical Areas were nested by state/territory. Left-censoring resulted in an attenuation of the unnested association to non-significance, while the nested association remained significantly positive. Cox regressions with simulated claims data demonstrated how left-censoring can reverse effects.

Conclusions

Collider bias can seriously confound work disability research, particularly cross-jurisdictional comparisons. Work disability researchers must grapple with this challenge by using appropriate study designs and analytical approaches, and considering how it affects the interpretation of results.

中文翻译：

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行政工人赔偿索赔数据中的对撞机偏差：跨辖区研究的挑战

目的

工人赔偿索赔包括严重到足以满足赔偿门槛的职业伤害。从理论上讲，具有更高阈值的系统应该有更少的索赔但更高的平均严重性。对于依赖索赔数据的研究，特别是补偿系统的跨辖区比较，这会导致对撞机偏差，从而导致虚假关联混淆分析。在这项研究中，我使用真实和模拟的索赔数据来证明对撞机偏差和用于解释它的方法的问题。

方法

使用澳大利亚索赔数据，我使用线性回归来检验索赔率与统计区域内的平均残疾持续时间之间的关联。通过按州/地区嵌套重复分析，以解释补偿系统中补偿阈值的变化。对左删失数据重复这两种分析。使用 Cox 生存分析对模拟索赔数据进行分析，以说明左审查如何逆转影响。

结果

统计区域内的索赔率与残疾持续时间呈负相关。但是，当统计区域按州/领地嵌套时，情况发生了逆转。左删失导致非嵌套关联衰减为不显着，而嵌套关联仍然显着为正。带有模拟索赔数据的 Cox 回归证明了左审查如何逆转影响。

结论

对撞机偏见会严重混淆工作障碍研究，尤其是跨司法管辖区的比较。工作障碍研究人员必须通过使用适当的研究设计和分析方法来应对这一挑战，并考虑它如何影响结果的解释。