Seshamani Meena, Gray Alastair
University of Pennsylvania School of Medicine, Philadelphia, USA.
Health Econ. 2004 Apr;13(4):303-14. doi: 10.1002/hec.826.
Zweifel and colleagues have previously proposed that proximity to death is a more important influence on health-care costs than age, suggesting that demographic change per se will not have a large impact on future aggregate health expenditure. However, issues of econometric methodology have led to challenges of the robustness of these findings. This paper revisits the analysis. Using a longitudinal hospital data set from Oxfordshire, England, the two-step Heckman model from the Zweifel study is first replicated, to find that neither age nor proximity to death have a significant effect on hospital costs. Econometric problems with the model are demonstrated, and instead a two-part model shows both age and proximity to death to have significant effects on quarterly hospital costs. Cost predictions, calculated with bootstrapped 95% confidence intervals, further demonstrate that while age may significantly affect quarterly costs, these cost changes are small compared to the tripling of quarterly costs that occurs with approaching death in the last year of life. The analyses show the importance of model selection to properly assess the determinants of health-care expenditures.
茨魏费尔及其同事此前曾提出，接近死亡对医疗保健成本的影响比年龄更为重要，这表明人口结构变化本身对未来总体医疗支出不会产生重大影响。然而，计量经济学方法问题给这些研究结果的稳健性带来了挑战。本文重新审视了这一分析。利用来自英国牛津郡的纵向医院数据集，首先复制了茨魏费尔研究中的两步赫克曼模型，结果发现年龄和接近死亡对医院成本均无显著影响。文中展示了该模型存在的计量经济学问题，取而代之的是一个两部分模型，该模型表明年龄和接近死亡对季度医院成本均有显著影响。通过自抽样法计算的95%置信区间得出的成本预测结果进一步表明，虽然年龄可能会显著影响季度成本，但与生命最后一年接近死亡时季度成本增长两倍相比，这些成本变化较小。分析表明模型选择对于正确评估医疗保健支出的决定因素非常重要。
