Hypertension is a common chronic condition, but the burden of emergency department (ED) visits due to hypertension and associated patient and hospital characteristics are not well described. The goals of this study were to (1) establish the burden of hypertension-related ED visits, estimated by the total number, proportion of adult visits, and population-based rate, (2) evaluate for change over time, and (3) identify associated patient and hospital characteristics. The Nationwide Emergency Department Sample from 2006 to 2012 was used to identify hypertension-related ED visits ( International Classification of Diseases, Ninth Revision, Clinical Modification codes 401 to 405, inclusive, and 437.2), and this was linked to US Census Bureau July population estimates to determine population-based rates for each study year. Negative binomial regression was performed to determine whether rates of hypertension-related ED visits changed over time. A total of 165,946,807 hypertension-related ED visits occurred during the 7-year study period (23.6% of all adult ED visits), and hypertension was the primary diagnosis for 6,399,088 (0.9% of all adult ED visits). The estimated yearly incidence rate increased 5.2% per year (incident rate ratio, 1.052; 95% confidence interval, 1.044 to 1.061; p <0.001) for hypertension-related visits and 4.4% per year (incidence rate ratio, 1.044; 95% confidence interval, 1.038 to 1.051; p <0.001) for ED visits with a primary diagnosis of hypertension. Over the same time, the proportion hospitalized decreased and the proportion of visits increased at safety net hospitals and among uninsured patients. In conclusion, these data indicate that hypertension-related ED visits are common and increasing.
Hypertension is a common and costly disease that increases the risk of heart attack, stroke, heart failure, renal failure, and death. Uncontrolled hypertension for even a few weeks is associated with increased risk of acute cardiovascular events and death. From 2000 to 2011, hospitalizations for hypertension increased more than 27%, and from 2003 to 2006, the cost of hypertension-associated hospitalizations was $113 billion, or 15% of all hospital costs. In the United States (US), there are an estimated 136.3 million emergency department (ED) visits annually or 44.5 per 100 adults. Increasingly, Americans seek ED care for chronic conditions or acute manifestations of chronic disease. Elevated blood pressure is common during ED visits, and total hospitalizations for hypertension have increased over time. Chronic conditions such as hypertension that have traditionally been managed in primary care clinics are being evaluated and treated with greater frequency in the ED. Using a national administrative database, the goals of this study were to (1) establish the burden of hypertension-related ED visits, estimated by the total number, proportion of adult visits, and population-based rate, (2) evaluate for change over time, and (3) identify associated patient and hospital characteristics.
Methods
We conducted a descriptive epidemiologic analysis of hypertension-related ED visits from 2006 to 2012 using the Nationwide Emergency Department Sample (NEDS). NEDS is a publicly available database from the Healthcare Cost and Utilization Project maintained by the Agency for Healthcare Research and Quality and is the largest source of US ED administrative data. NEDS is designed to be representative of all ED visits and is constructed from the Healthcare Cost and Utilization Project State Emergency Department Databases and the State Inpatient Databases. In 2012, 30 states and 950 hospitals contributed data for 31 million ED visits, for an approximate 20% stratified sample of US hospital-based EDs. For each ED visit, there are up to 15 International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9 CM) codes, as well as more than 50 other patient, visit, hospital, and region-level variables. For hospitals included in NEDS, all ED visits from each institution are included. Weighting is required to calculate national estimates. Estimates of ED utilization using NEDS are similar to other national data sets, such as the National Hospital Ambulatory Medical Care Survey. This study was approved after institutional review board review.
We included adult (age ≥18 years) ED visits from 2006 to the end of 2012. Hypertension was identified by the following ICD-9 CM codes: 401 to 405 (inclusive) and 437.2. This combination of ICD-9 CM codes has been shown to have specificity of 0.95 and positive predictive value of 0.97 for identifying visits truly related to hypertension. “Hypertension-related ED visits” were defined as ED visits with any diagnosis code of hypertension. “ED visits with a primary diagnosis of hypertension” were defined ED visits in which hypertension was the first diagnosis code.
Comorbid conditions were identified using ICD-9 CM codes, where an asterisk indicates inclusion of subcodes : hypertension (401.1, 401.9, 405.1*, and 405.9*), diabetes (250.00, 250.01, 250.02, and 250.03), coronary artery disease (412, 414.00, 414.01, 414.02, 414.03, 414.04, 414.05, 414.06, 414.07, 414.8, and 414.9), chronic kidney disease (575*), heart failure (428*), chronic obstructive pulmonary disease (491*, 492*, and 496*), and cerebrovascular disease (430, 431, 432.0, 432.9, 434.01, 434.11, 434.91, and 435.9).
ED visits without hospitalization were considered outpatient ED visits. ED visits for uninsured patients were those classified as self-pay. Safety net hospitals were defined as: (1) >30% of ED visits for patients insured by Medicaid; (2) >30% of visits for patients without insurance; or (3) combined Medicaid and uninsured pool >40%.
Analyses were conducted in accordance with Agency for Healthcare Research and Quality recommendations, including weighting and stratification; all reported values are weighted. Using US Census Bureau July population estimates, incidence rates (annual and monthly) were calculated separately for hypertension-related ED visits and ED visits with a primary diagnosis of hypertension for each study year. Patient and hospital level characteristics were computed for each year of the study and for the entire study period of 7 years. Two negative binomial regression models were used to estimate the annual change in incidence rates for: (1) hypertension-related ED visits and (2) ED visits with a primary diagnosis of hypertension.
In exploratory analyses, annual incidence rates of hypertension-related ED visits were stratified by age (aged <45, 45 to 64, 65 to 79, and ≥80 years) and geographic region (Northeast, South, Midwest, and West, defined according to US census boundaries ). Given seasonal variation in blood pressure, monthly incidence rates were computed. To better understand conditions associated with ED visits for hypertension, the most common co-occurring diagnoses were determined for ED visits with a primary and, separately, secondary diagnosis of hypertension. Analyses were conducted using survey packages in SAS 9.4 (SAS Institute, Cary, North Carolina) and Stata 14 IC (STATA Corp, College Station, Texas).
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