Korsgaard Søren, Christiansen Christian Fynbo, Schmidt Morten, Sørensen Henrik Toft
Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
Clin Epidemiol. 2021 Nov 3;13:1051-1059. doi: 10.2147/CLEP.S334546. eCollection 2021.
Studies examining myocardial infarction (MI) often seek to include only incident MIs by excluding recurrent MIs. When based on historical data, identification of previous MI depends on the length of the look-back period. However, international registries often cover a short time period, consequently containing left-censored data, making it impossible to determine if a first MI in a period is truly an incident MI. We evaluated whether the proportion of MIs identified as recurrent MIs depends on the look-back period, and how including recurrent MIs in a planned incident MI cohort impacts survival estimates.
We used the Danish National Patient Registry, covering all Danish hospitals since 1977 to identify first MIs during 2010-2016 (index events). The hospital registry history preceding the index event was then searched for previous MIs. We plotted the proportion of index events identified as recurrent MIs as a function of the look-back period. Moreover, we calculated 5-year all-cause mortality and confidence intervals (CIs) using the 1-Kaplan-Meier method for five cohorts based on the index events and defined by look-back periods of 0, 5, 10, 20, and up to 39 years.
Among 63,885 index events, 3.4% were identified as recurrent MIs with 5 years of look-back, 7.9% with 10 years, 14% with 24 years, and 15% with up to 39 years. All-cause mortality risk was 36% (95% CI: 36-37%) with 0 years of look-back, 35% (95% CI: 35-36%) with 5 years, 35% (95% CI: 35-36%) with 10 years, 34% (95% CI: 34-35%) with 20 years, and 34% (95% CI: 33-34%) with up to 39 years.
Most recurrent MIs were identified with a look-back period of 24 years. Including recurrent MIs in a planned incident MI cohort, due to shorter look-back periods, overestimated the mortality risk.
研究心肌梗死（MI）时，通常试图通过排除复发性心肌梗死来仅纳入首次发生的心肌梗死。基于历史数据时，既往心肌梗死的识别取决于回顾期的长短。然而，国际注册研究通常涵盖的时间段较短，因此包含左删失数据，这使得无法确定某一时期的首次心肌梗死是否真的是首次发生的心肌梗死。我们评估了被识别为复发性心肌梗死的心肌梗死比例是否取决于回顾期，以及将复发性心肌梗死纳入计划中的首次心肌梗死队列对生存估计有何影响。
我们使用丹麦国家患者注册数据库，该数据库涵盖自1977年以来丹麦所有医院，以识别2010 - 2016年期间的首次心肌梗死（索引事件）。然后在索引事件之前的医院注册记录中查找既往心肌梗死。我们绘制了被识别为复发性心肌梗死的索引事件比例随回顾期变化的函数图。此外，我们使用1 - Kaplan - Meier方法为五个基于索引事件且由0、5、10、20和长达39年的回顾期定义的队列计算5年全因死亡率和置信区间（CI）。
在63,885例索引事件中，5年回顾期内有3.4%被识别为复发性心肌梗死，10年回顾期内为7.9%，24年回顾期内为14%，长达39年回顾期内为15%。回顾期为0年时，全因死亡风险为36%（95%CI：36 - 37%），5年时为35%（95%CI：35 - 36%），10年时为35%（95%CI：35 - 36%），20年时为34%（95%CI：34 - 35%），长达39年时为34%（95%CI：33 - 34%）。
大多数复发性心肌梗死是通过24年的回顾期识别出来的。由于回顾期较短，将复发性心肌梗死纳入计划中的首次心肌梗死队列会高估死亡风险。
