Background Research on influenza burden in adults has focused on crude subgroups with cut-points at 65-years, limiting insight into how burden varies with increasing age. This study describes the incidence of influenza-related outpatient visits, emergency room (ER) visits, and hospitalizations, along with healthcare resource use and complications in the aging adult population. Methods Individuals ≥18 years of age in the United States were evaluated retrospectively in five seasonal cohorts (2015–2020 seasons) in strata of age with 5-year increments. Person-level electronic medical records linked to pharmacy and medical claims were used to ascertain patient characteristics and outcomes. Influenza-related medical encounters were identified based on diagnostic codes (ICD-10 codes J09*–J11*). Results Incidence of influenza-related outpatient visits was highest among people aged 18–34 years and declined with increasing age. For ER visits, incidence tended to be elevated for people aged 18–34 years, relatively stable from 35 through 60, and increased rapidly after 60. Hospitalization incidence remained relatively stable until about 50 years of age and then increased with age. One in three patients was diagnosed with pneumonia after hospitalization, regardless of age. Across seasons, age groups, and clinical settings, on average, 40.8% of individuals were prescribed antivirals and 17.2% antibiotics. Conclusions Incidence of influenza-related hospitalizations begins to increase around age 50 rather than the more common cut-point of 65, whereas incidence of outpatient visits was highest among younger adults. Influenza infections frequently led to antiviral and antibiotic prescriptions, underscoring the role influenza vaccination can play in combating antimicrobial resistance.

中文翻译：

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2015-2020 年流感季节美国各成人年龄段流感相关医疗事件发生率以及相关医疗资源使用和并发症

背景 对成人流感负担的研究主要集中在以 65 岁为分界点的粗略亚组上，限制了对负担如何随年龄增长而变化的了解。这项研究描述了与流感相关的门诊就诊、急诊室就诊和住院治疗的发生率，以及老年人群中医疗资源的使用和并发症。方法对美国 18 岁以上的个体进行回顾性评估，分为五个季节性队列（2015-2020 赛季），年龄层以 5 岁为增量。与药房和医疗索赔相关的个人电子病历用于确定患者特征和结果。与流感相关的医疗事件是根据诊断代码（ICD-10 代码 J09*–J11*）确定的。结果 18~34岁人群流感相关门诊发病率最高，并随年龄增长而下降。对于急诊就诊，18-34岁人群的发病率趋于升高，35-60岁人群相对稳定，60岁后迅速增加。住院发病率在50岁左右之前保持相对稳定，然后随着年龄的增长而增加。无论年龄大小，三分之一的患者在住院后被诊断出患有肺炎。在不同季节、年龄组和临床环境中，平均有 40.8% 的人服用抗病毒药物，17.2% 的人服用抗生素。结论 流感相关住院发生率在 50 岁左右开始增加，而不是更常见的临界点 65 岁，而门诊就诊发生率在年轻人中最高。流感感染经常导致患者开出抗病毒药物和抗生素处方，这凸显了流感疫苗接种在对抗抗菌药物耐药性方面的作用。