Increasing Trend in Admissions for Malignant Hypertension and Hypertensive Encephalopathy in the United States

Malignant hypertension and hypertensive encephalopathy are life-threating manifestations of hypertension. These syndromes primarily occur in patients with a history of poorly controlled hypertension. The purpose of this study was to investigate national trends in hospital admissions for malignant hypertension, hypertensive encephalopathy, and essential hypertension. This was a retrospective cohort study that used the Nationwide Inpatient Sample. We identified all hospitalizations between 2000 and 2011, during which a primary diagnosis of malignant hypertension (ICD 9 code: 401.0), hypertensive encephalopathy (ICD 9 code: 437.2), or essential hypertension (ICD 9 code: 401.9) was recorded. Time series models were estimated for malignant hypertension, hypertensive encephalopathy, essential hypertension and also for the combined series. A piecewise linear regression analyses was performed to investigate whether there were changes in the trends of these series. In addition, we also compared the characteristics of patients with these diagnoses. The estimated number of admissions for both malignant hypertension and hypertensive encephalopathy increased dramatically after 2007, whereas discharges for essential hypertension fell, and there was no change in trend for the combined series. Costs rose substantially for patients with these diagnoses after 2007, but mortality significantly fell for malignant hypertension and mortality for hypertensive encephalopathy did not change. The dramatic increase in the number of hospital admissions for hypertensive encephalopathy and malignant hypertension should have resulted in dramatic increases in morbidity, but it did not. The change is most likely related to changes in coding related to diagnostic-related groups that occurred in 2007.