Hospitalizations for mitochondrial disease across the lifespan in the U.S.

IMPORTANCE: Mitochondrial disease is being diagnosed with increasing frequency. Although children with mitochondrial disease often have severe, life-limiting illnesses, many survive into adulthood. There is, however, limited information about the impact of mitochondrial disease on healthcare utilization in the U.S. across the lifespan.
OBJECTIVES: To describe the characteristics of inpatient hospitalizations related to mitochondrial disease in the U.S., to identify patient-level clinical factors associated with in-hospital mortality, and to estimate the burden of hospitalizations on individual patients.
DESIGN: Cross-sectional and longitudinal observational studies.
SETTING: U.S. hospitals. PARTICIPANTS: Individuals with hospital discharges included in the triennial Healthcare Cost and Utilization Project (HCUP) Kids Inpatient Database (KID) and the National Inpatient Sample (NIS) in 2012 (cross-sectional analysis); individuals with hospital discharges included in the HCUP California State Inpatient Database from 2007 to 2011, inclusive (longitudinal analysis). EXPOSURE: Hospital discharge associated with a diagnosis of mitochondrial disease. MAIN OUTCOME MEASURES: Total number and rate of hospitalizations for individuals with mitochondrial disease (International Classification of Diseases, 9th revision, Clinical Modification code 277.87, disorder of mitochondrial metabolism); in-hospital mortality.
RESULTS: In the 2012, there were approximately 3200 inpatient pediatric hospitalizations (1.9 per 100,000 population) and 2000 inpatient adult hospitalizations (0.8 per 100,000 population) for mitochondrial disease in the U.S., with associated direct medical costs of $113million. In-hospital mortality rates were 2.4% for children and 3.0% for adults, far exceeding population averages. Higher socioeconomic status was associated with both having a diagnosis of mitochondrial disease and with higher in-hospital mortality. From 2007 to 2011 in California, 495 individuals had at least one admission with a diagnosis of mitochondrial disease. Patients had a median of 1.1 hospitalizations (IQI, 0.6-2.2) per calendar year of follow-up; infants under 2y were hospitalized more frequently than other age groups. Over up to five years of follow up, 9.9% of participants with any hospitalization for mitochondrial disease were noted to have an in-hospital death. CONCLUSIONS AND RELEVANCE: Hospitalizations for pediatric and adult mitochondrial diseases are associated with serious illnesses, substantial costs, and significant patient time. Identification of opportunities to prevent or shorten such hospitalizations should be the focus of future studies.