Age- and Sex-Specific In-Hospital Mortality after Myocardial Infarction in Routine Clinical Practice

SAGE-Hindawi Access to Research Cardiology Research and Practice Volume 2010, Article ID 752765, 11 pages doi:10.4061/2010/752765 Clinical Study Age- and Sex-Specific In-Hospital Mortality after Myocardial Infarction in Routine Clinical Practice Chizobam Ani,1 Deyu Pan,1 David Martins,2, 3 and Bruce Ovbiagele4 1 Department of Family Medicine, Charles Drew University of Medicine and Science, Los Angeles, CA 90059-2518, USA 2 Department of Internal Medicine, Charles Drew University of Medicine and Science, Los Angeles, CA 90059-2518, USA 3 Department of Internal Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA 4 Department of Neurology and Stroke Center, University of California at Los Angeles, Los Angeles, CA 90095, USA Correspondence should be addressed to Chizobam Ani, Received 22 October 2010; Accepted 9 December 2010 Academic Editor: H. O. Ventura Copyright © 2010 Chizobam Ani et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Literature regarding the influence of age/sex on mortality trends for acute myocardial infarction (AMI) hospitalizations is limited to hospitals participating in voluntary AMI registries. Objective. Evaluate the impact of age and sex on in-hospital AMI mortality using a nationally representative hospital sample. Methods. Secondary data analysis using AMI hospitalizations identified from the Nationwide-Inpatient-Sample (NIS). Descriptive and Cox proportional hazards analysis explored mortality trends by age and sex from 1997–2006 while adjusting for the influence of, demographics, co-morbidity, length of hospital stay and hospital characteristics. Results. From 1997–2006, in-hospital AMI mortality rates decreased across time in all subgroups (P < .001), except for males aged <55 years. The greatest decline was observed in females aged <55 years, compared to similarly aged males, mortality outcomes were poorer in 1997-1998 (RR 1.47, 95% CI = 1.30–1.66), when compared with 2005-2006 (RR 1.03, 95% CI = 0.90–1.18), adjusted P value for trend demonstrated a statistically significant decline in the relative AMI mortality risk for females when compared with males (<0.001). Conclusion. Over the last decade, in-hospital AMI mortality rates declined for every age/sex group except males <55 years. While AMI female-male mortality disparity has narrowed, some room for improvement remains. 1. Introduction Cardiovascular disease is the leading cause of death and disability in the United States, accounting for the underlying cause of death for about 1 in 2.8 deaths in the United States [1, 2]. Fortunately, observations over the last 20 years suggest that death rates following an index AMI are steadily declining [3–7], largely due to effective drugs and revascularization procedures [8, 9]. Recent evidence also indicates that the hitherto reported sex disparity: higher mortality rates after AMI in young females relative to their similarly aged male counterparts may be diminishing [10–13]. However, many of the aforementioned studies obtained data from registries comprising hospitals that voluntarily signed up for participation or focused only on a specific age group (e.g., >65 years) and thus may not be broadly representative. Indeed, hospitals participating in these registries tend to differ from nonparticipating hospitals by being larger, more procedure-oriented centers with a major interest in the improvement of quality metrics and processes [14]. Using widely representative hospital administrative data, the main objective of this study was to assess trends in ageand sex-specific in-hospital mortality after AMI in the United States. A secondary objective was to examine recent nationwide patterns in the use of common procedures during AMI hospitalization by sex and age. 2. Methods Data were obtained from the Nationwide Inpatient Sample (NIS), developed as part of the Healthcare Cost and Utilization Project (HCUP), a Federal-State-Industry Cardiology Research and Practice Female versus male mortality rate 4 3.5 3 2.5 2 1.5 1 0.5 0 RR Mortality (%) 2 1997-1998 1999-2000 2001-2002 2003-2004 2005-2006 Male Female 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 Female-male AMI mortality HR trend: age <55 years R2 = 0.8327 1997-1998 1999-2000 2001-2002 2003-2004 2005-2006 Lower CI Linear (RR) RR Upper CI (a) (b) Figure 1: In-hospital AMI mortality rate and relative mortality trend (female versus male) by NIS year for age <55 years. partnership sponsored by the Agency for Healthcare Research and Qual ity (AHRQ) [15]. NIS is designed to approximate a stratified 20% sample of all non-Federal, short-term, general, and specialty hospitals serving adults in the United States. The sampling strategy selects hospitals within states that have State Inpatient Databases (SID) according to defined strata based on ownership, bed size, teaching status, urban/rural location, and region. All discharges from sampled hospitals for the calendar year are then selected for inclusion into NIS. To allow for national estimate extrapolation, both hospital and discharge weights were provided. Detailed information on the design of the NIS is available at http://www.hcup-us.ahrq.gov. From 1997 to 2006, NIS captured discharge-level information on primary and secondary diagnoses and procedures, discharge vital status, and demographics on discharges per year. Data elements that could directly or indirectly identify individuals were excluded; we thus considered all discharges to be independent. The unit of analysis was the discharge rather than the individual. A unique hospital iden tifier allows for linkage of discharge data to an NIS data set with hospital characteristics. To analyze myocardial infarction hospitalizations, we identified all discharges for which an ICD9-CM code of 410.xx (acute myocardial infarction including STEMI and NSTEMI) was listed as the primary diagnosis. This approach has been utilized by other studies and was taken to specifically focus on patients who presented with acute myocardial infarction and not those patients who had AMI secondary to other conditions like, surgery, hypotension, or other events post hospitalization. Total numbers of myocardial infarctions were obtained by summing across codes. Similarly procedure codes for the ten most common procedures were also identified using the reported ICD9-CM code. We accounted for procedure code changes that occurred in 2005 while extracting the data (single vessel percutaneous transluminal coronary angioplasty [PTCA] or coronary atherectomy with and without a thrombolytic agent; 36.01 and 36.02). This secondary data analysis study was approved by the Charles R Drew University of Medicine and Science IRB. 3. Statistical Analyses We compared trends in-hospital AMI mortality in males and females before and af (...truncated)