Lymphedema is a disabling condition both underdiagnosed and undertreated. Epidemiological data on this disease is sparse.

The prevalence of lymphedema was studied in hospitalized patients registered in the Nationwide Inpatient Sample (NIS) of the United States (US) during the period 2016-2020. ICD-10 codes related to lymphedema were utilized to identify eligible cases. A descriptive epidemiological analysis was performed to investigate comorbidity burden. Furthermore, clinical outcomes during hospitalizations were analyzed, including in-hospital fatality, length of stay and total charges per hospitalization.

Patients with lymphedema represented 0.5% (n=795,770 of whom n=7440 hereditary) of hospitalizations between 2016 and 2020; the annual numbers increased from 143,320 in 2016 to 176,460 in 2019, subsequently falling to 162,585 in 2020. Patients with lymphedema had a median age of 67 (IQR: 57-77) years; 59% were female. Overall, hospitalizations of patients with lymphedema peaked in summer (July). The majority of lymphedema-related hospitalizations were emergency admissions (90%), often in association with phlegmon (39%), wounds (16%), psychiatric disorders due to substance abuse (13%), or venous thromboembolism (5.7%). The most frequent comorbidities were arterial hypertension (76%), chronic pulmonary disease (31%) and cancer (24%). The in-hospital fatality rate was 2.3%, the median length of stay was 5 (IQR: 3-8) days, and each hospitalization incurred a median of 36,038 (IQR: 20,251-66,782) US dollars, which was roughly three times higher than average hospitalization costs in the NIS in the same period. Furthermore, in multivariable analyses venous thromboembolism (OR: 1.71; 95%CI 1.50-1.95), cancer (OR: 1.47; 95%CI 1.36-1.60), and cerebro-cardiovascular diseases (OR: 1.45; 95%CI 1.27-1.65) were associated with higher case fatality rates, while the main drivers of the length of hospitalization were venous thromboembolism (beta: 2.01; 95%CI: 1.71;2.31), paralysis (beta: 1.92; 95%CI: 0.43;3.41), wounds (beta: 1.14; 95%CI: 0.99;1.28) and dementia (beta: 0.95; 95%CI: 0.75;1.15) .

This represents the first comprehensive nationwide study of the in-hospital epidemiological and economic burden of lymphedema in the US. The findings highlight that lymphedema, although underdiagnosed, affects a significant number of patients.