Economic burden and secondary complications of influenza-related hospitalization among adults in the US: a retrospective cohort study

This study aims to describe the healthcare resource utilization (HCRU) and direct medical cost of influenza-related hospitalizations to illustrate the persistent economic burden of influenza among adults in the US. A retrospective cohort study was conducted using the PINC AI Healthcare Database. Adults hospitalized with a diagnosis of influenza between August 1–May 31 from 2016–2023 were identified and stratified by age (18–49, 50–64 and ≥65 years). The index hospitalization was defined as the individual’s first influenza-related hospitalization during each season. Patient demographics, comorbidities, and hospitalization characteristics were assessed during the index hospitalization. Index hospitalization length of stay (LOS), in-hospital mortality, intensive care unit (ICU) admissions, mechanical ventilation (MV) usage, and costs were evaluated overall and by MV usage, ICU admission, and secondary complication status. Pre-index influenza-related outpatient and emergency department (ED) visits (7 days prior) were also evaluated. Primarily initiated in the ED, the median LOS for influenza-related hospitalizations was 3–4 days. Inpatient mortality increased with age (2.2–4.4%). Combined mean hospitalization and initial ED visit costs were $12,556–$14,494 (2017/18; high severity season) and $11,384–$12,896 (2022/23; most recent season). Compared to other age groups, adults ≥65 years had higher proportions of hospitalization with no MV or ICU usage. Adults 18–49 years had the highest proportion of ICU admission only, whereas adults 50–64 years had the highest MV usage only and both MV and ICU admission. MV and/or ICU usage was associated with higher hospitalization costs. Increasing proportionally with age, the majority of influenza-related hospitalizations had a secondary complication diagnosis, which were associated with elevated costs. Analysis of this hospital-based administrative database relied on coding accuracy. Only hospital system-associated outpatient/ED visits were captured; the full scope of HCRU was under-ascertained. The economic burden of influenza-related hospitalizations remains substantial, driven by underlying conditions, MV/ICU usage and secondary complications. This study described the healthcare resource utilization (HCRU) and costs for US adults ≥18 years old hospitalized with influenza and associated secondary complications such as pneumonia, asthma exacerbation and malignant hypertension between 2016–2023. The researchers analyzed a hospital admission database and found that, for the healthcare system, average cost per influenza-related hospitalization ranged from $11,384 to $14,494, depending on the influenza season and age of the patient. Over 96% of patients admitted to a hospital initially presented at the emergency department, 20–30% of patients required mechanical ventilation (MV) or intensive care unit (ICU) admission, and the median hospital length of stay was 3–4 days. This study adds to the existing evidence by providing economic burden estimates for the 2022/23 influenza season, the most recent influenza season after the COVID-19 pandemic, and found slightly lower HCRU and cost for influenza hospitalizations relative to prior seasons. Also, the study comprehensively analyzed economic burden by patient age groups and found lower HCRU and costs among patients ≥65 years compared to adults 18–49 years and 50–64 years consistently for all seasons. Additionally, the study found that the proportion of patients with MV usage alone, with MV usage and an ICU admission, and average hospitalization costs were greatest among patients 50–64 years, highlighting the potential benefit of increasing rates of seasonal influenza vaccination among this age group. Finally, the study found higher costs among patients with complications related to their influenza infection compared to patients without complications. Overall, the study found that influenza-related hospitalization can contribute to substantial economic burden in the US in the most recent time period.

本研究旨在描述流感相关住院的医疗资源利用（healthcare resource utilization, HCRU）与直接医疗成本，以阐明美国成人群体中流感持续存在的经济负担。本研究采用PINC AI医疗数据库（PINC AI Healthcare Database）开展回顾性队列研究。纳入2016-2023年8月1日至5月31日期间因确诊流感住院的成人受试者，并按年龄分层（18-49岁、50-64岁及≥65岁）。将受试者在每个流感季内的首次流感相关住院定义为指数住院。对指数住院期间的患者人口学特征、合并症及住院特征进行评估，并从整体层面及按机械通气（mechanical ventilation, MV）使用情况、重症监护病房（intensive care unit, ICU）收治情况与继发并发症状态分层，评估指数住院的住院时长（length of stay, LOS）、住院死亡率、ICU收治率、MV使用情况及住院成本。此外，还对指数住院前7天内的流感相关门诊及急诊（emergency department, ED）就诊情况进行分析。研究结果显示，流感相关住院患者多首诊于急诊，中位住院时长为3-4天；住院死亡率随年龄增长而升高（2.2%-4.4%）。合并住院与初始急诊就诊的平均总成本在2017/18流感季（重症高发季）为12556-14494美元，在2022/23流感季（最新流感季）为11384-12896美元。与其他年龄组相比，≥65岁成人未使用MV或未入住ICU的住院占比更高；18-49岁成人仅需ICU收治的比例最高，而50-64岁成人仅需MV使用、同时需MV与ICU收治的比例均为最高。使用MV和/或入住ICU与更高的住院成本相关。继发并发症诊断的流感相关住院占比随年龄增长呈正比升高，且此类患者的住院成本显著升高。本研究基于医院管理数据库开展分析，依赖于编码准确性；仅捕获了与医院系统关联的门诊/急诊就诊情况，因此医疗资源利用的完整范围存在低估。流感相关住院的经济负担依然可观，其驱动因素包括基础疾病、MV/ICU使用及继发并发症。本研究针对2016-2023年美国≥18岁因流感住院且合并肺炎、哮喘急性发作、恶性高血压等继发并发症的成人群体，分析了其医疗资源利用与成本情况。研究团队通过分析住院入院数据库发现，按流感季与患者年龄不同，每例流感相关住院的平均成本介于11384美元至14494美元之间。超过96%的住院患者首诊于急诊，20%-30%的患者需MV支持或ICU收治，中位住院时长为3-4天。本研究补充了现有证据：首次针对新冠疫情后最新的2022/23流感季提供了经济负担估算数据，且发现该季的流感住院医疗资源利用与成本较既往季候略低。此外，本研究按患者年龄组全面分析了经济负担，发现所有流感季中，≥65岁患者的医疗资源利用与成本均低于18-49岁及50-64岁成人。研究还发现，仅使用MV、同时使用MV与ICU收治的患者占比及平均住院成本在50-64岁年龄组中最高，这凸显了为该年龄群体提升季节性流感疫苗接种率的潜在益处。此外，合并流感感染相关并发症的患者，其住院成本显著高于无并发症患者。总体而言，本研究证实，在近期时间段内，流感相关住院仍会给美国医疗系统带来可观的经济负担。