Yale School of Medicine, PO Box 208034, New Haven, CT 06520, USA.
Stroke. 2013 Feb;44(2):531-3. doi: 10.1161/STROKEAHA.112.670547. Epub 2013 Jan 8.
A systematic review found an association between the July start of internships and residencies and higher mortality rates for hospitalized patients, but data related to stroke are limited. We assessed seasonal variations in 30-day risk-adjusted mortality rates (RAMRs) after ischemic stroke by hospital teaching status.
The analysis included all fee-for-service Medicare beneficiaries aged ≥ 65 years with a primary discharge diagnosis of ischemic stroke (International Classification of Diseases, 9th revision, codes 433, 434, and 436) from 1999 to 2006. Hierarchical linear regression models calculated RAMRs, adjusting for patient demographics and comorbidities. Annual data were combined and reconstructed for time series analyses; RAMRs were calculated for each month. Structural models compared monthly seasonal patterns stratified by hospital teaching status.
Of 2 824 694 ischemic stroke discharges, 51.7% were from teaching hospitals. There were seasonal patterns within each calendar year, with the highest 30-day RAMR in the winter and the lowest in the summer, but with a smaller peak in July. Thirty-day RAMRs decreased from 1999 to 2006, as did seasonal variations within each calendar year. Seasonal patterns were similar for teaching and nonteaching hospitals.
The 30-day RAMR decreased overall, but seasonal patterns were present, with the highest RAMR in January and a smaller peak in July. Because patterns were similar for teaching and nonteaching hospitals, the July peak cannot be explained by the introduction of new trainees in the beginning of the academic year. The reasons for these seasonal patterns warrant further investigation.
一项系统评价发现，实习和住院医师培训从 7 月开始与住院患者的死亡率升高有关，但与中风相关的数据有限。我们评估了医院教学状态与缺血性中风后 30 天风险调整死亡率（RAMR）之间的季节性变化关系。
分析纳入了 1999 年至 2006 年所有符合条件的 Medicare 受益人的数据，这些患者年龄均≥65 岁，初次出院诊断为缺血性中风（国际疾病分类第 9 版，代码 433、434 和 436）。采用分层线性回归模型，调整患者的人口统计学和合并症因素，计算 RAMR。对年度数据进行合并和时间序列分析重构；为每个月计算 RAMR。结构模型比较了按医院教学状态分层的月度季节性模式。
在 2824694 例缺血性中风出院患者中，51.7%来自教学医院。每年都存在季节性模式，冬季 30 天 RAMR 最高，夏季最低，但 7 月的峰值较小。从 1999 年到 2006 年，30 天 RAMR 下降，每年的季节性变化也随之下降。教学医院和非教学医院的季节性模式相似。
尽管整体 30 天 RAMR 下降，但仍存在季节性模式，1 月 RAMR 最高，7 月峰值较小。由于教学医院和非教学医院的模式相似，因此，7 月的高峰不能用学年开始时新学员的介入来解释。这些季节性模式的原因值得进一步研究。
