Race and Gender Differences in Acute Respiratory Distress Syn

Abstract and Introduction

Objective: Acute respiratory distress syndrome (ARDS) is a devastating clinical disorder that affects critically ill patients with a wide variety of underlying illnesses. Presently, there is limited population-based information concerning both the impact of ARDS on mortality, and the effects of race and gender on national ARDS mortality rates. In this study, we have attempted to evaluate trends over an 18-yr period in deaths associated with ARDS in the United States.
Design: Case series.
Patients: The Multiple-Cause Mortality Files compiled by the National Center for Health Statistics from 1979-1996 contains information on 38,263,780 decedents. We identified 333,004 decedents who had ARDS.
Measurements and Main Results: We calculated age-adjusted annual ARDS mortality rates. The annual age-adjusted mortality rate for ARDS initially increased from 1979 (5.0 deaths per 100,000 individuals) to 1993 (8.1 deaths per 100,000 individuals). From 1993 to 1996, the mortality rate for ARDS decreased significantly to 7.4 deaths per 100,000 individuals. Annual ARDS mortality rates have been continuously higher for men when compared with women and for African-Americans when compared with white decedents and decedents of other racial backgrounds. When decedents were stratified by race and gender, African-American men had the highest ARDS mortality rates in comparison to all other subgroups (mean annual mortality rate of 12.8 deaths per 100,000 African-American men).
Conclusions: Although the annual ARDS mortality rate is slowly declining in the United States, significant race and gender differences in ARDS mortality exist.

The acute respiratory distress syndrome (ARDS) was first officially described in 1967 and is characterized by the sudden onset of severe hypoxemia and diffuse bilateral pulmonary infiltrates in the absence of acute congestive heart failure.^[1] ARDS occurs in critically ill patients with a wide variety of underlying illnesses and frequently occurs in patients without any preexisting history of lung disease.^[2,3] Although our understanding of the pathogenesis of ARDS has grown substantially over the last three decades, there have been only minor advances in the understanding of the epidemiology of ARDS.^[4]

There are clearly discrepancies in the prevalence and severity of several medical conditions on the basis of race and gender. In regard to race, African-Americans have a higher prevalence of essential hypertension.^[5] There are several well-publicized differences in cardiovascular care and outcome according to race.^[6] In the oncology literature, African-Americans have a higher risk of developing ovarian cancer and a worse outcome from breast cancer.^[7,8] In the field of pulmonary medicine, sarcoidosis has been estimated to be 10 to 17 times more prevalent in African-Americans when compared with whites in the Unites States.^[9,10] In addition, African-American men consistently had a higher lung cancer prevalence and mortality during the 1970s and 1980s when compared with white men.^[11] However unlike these other medical subspecialties, clinical studies concerning race and gender differences in critical care medicine are severely lacking.^[12,13,14]

One explanation for a deficiency in studies that examine race and gender differences in critically ill patients, and specifically those with ARDS, may be that the majority of epidemiologic studies involving these patients are based on data from single institutions. These registries have the advantage of systematically collecting predefined data on a relatively large number of patients over time.^[15] However, information from these single institution studies may not generalize to other clinical settings and may not be large enough to identify important epidemiologic trends.

Recently, we examined possible racial differences in ARDS mortality by using the 1993 National Mortality Followback Study database, which is a comprehensive survey of 22,957 decedents or 1% of all of the total annual deaths in the United States. Using proportional mortality ratios, we identified a positive association between ARDS mortality and nonwhite race.^[16] In this present study, we have analyzed the 1979 to 1996 Multiple-Cause Mortality Files to determine the effects of race and gender on ARDS mortality and to estimate annual ARDS mortality rates for the entire United States over an 18-yr period.

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