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Construct Overview of Mortality

Please note that this section is an archive and is no longer being updated.

Background

Mortality is simply defined as a ratio of the number of deaths to the total population of interest. Mortality is an important concept in the healthcare environment as it is related to the quality of patient care, treatment effectiveness, and understanding of the etiology and course of disease. Data used to estimate mortality are collected by most governments and are readily available.¹ In the U.S., we rely on the CDC's National Center for Health Statistics (NCHS) to provide data on mortality via the National Vital Statistics System (NVSS). These data are based on birth and death events at local and state levels.

Death events from state data are housed in a central electronic index, the National Death Index (NDI), implemented in 1981.² After death certificates are collected at a local level, death data are compiled from county and state levels and sent from the state to the NCHS. The NDI includes death events from 1979 onward. An additional feature implemented in 1997, NDI Plus, made it possible to locate the cause of death based on ICD-9 codes. If researchers wish to use the NDI for statistical purposes, they must submit an application to the NCHS to be reviewed and approved over the course of a few months.³

VA Relevance

The Department of Veterans Affairs uses a database known as the Beneficiary Identification and Records Locator Subsystem (BIRLS) to house vital status data, in addition to the widely used Patient Treatment File (PTF). The BIRLS contains records of all veteran beneficiaries and includes veterans whose survivors made application for death benefits, veterans discharged since March 1973, and Medal of Honor and VA education benefit awardees.⁴ The BIRLS database contains records from pre-Civil War to present day. Cause of death is not coded in the BIRLS. The BIRLS Death File is available as a SAS dataset and may be accessed by VA investigators. Those interested in using this dataset should contact the Austin Automation Center (AAC).

The PTF is a database that contains data on inpatient veterans. Date of death from October 1991 to present day is available in the PTF Main File, which also includes demographic and summary data (i.e. date of admission, medical facility).³

Researchers suggest that to increase accuracy, both the BIRLS and PTF should be used to assess mortality in the VA.³ Other research has indicated that veterans' mortality assessment may be improved by using VA data and death certificates.⁴

Measurement

Simple death rates are typically derived from administrative data, such as from the NDI and BIRLS. Reporting of deaths is typically fairly accurate as it is hard to misclassify, although the reporting of cause of death is more prone to error as it relies on the assigning and entering of diagnostic codes, such as the ICD codes.¹ In determining the sensitivity and specificity of mortality sources, the death certificate is typically considered to be the gold standard criterion.³

Standard off-the-shelf instruments are not used to assess mortality. Rather, in addition to administrative data, clinicians and researchers use mortality prediction models, which are scoring systems designed to estimate an individual's risk of dying. There are numerous scoring systems designed for specific diseases and age cohorts, and also generic scoring systems. Three commonly accepted generic scoring systems are the Acute Physiology and Chronic Health Evaluation (APACHE), Simplified Acute Physiology Score (SAPS), and Mortality Probability Model (MPM). These three models are briefly described below.

Most Frequently Cited Instruments

1. Acute Physiology And Chronic Health Evaluation (APACHE)
   [4,182 Citations]
2. Simplified Acute Physiology Score (SAPS)
   [1,101 Citations]
3. Mortality Probability Model (MPM)
   [324 Citations]

1. WHO Collaborating Center for Health Technology Assessment. 2004. Measuring Health and Mortality. Accessed July 2005. Available: http://www.iph.uottawa.ca/whohta/projects/eo_toolkit/chp1/ch1a_c.htm
2. National Center for Health Statistics. 2005. National Vital Statistics System. Accessed July 2005. Available: http://www.cdc.gov/nchs/data/factsheets/nvss.pdf
3. Cowper DC, Kubal JD, Maynard C, Hynes DM. A primer and comparative review of major US mortality databases. Ann Epidemiol. 2002 Oct;12(7):462-8. PMID: [Abstract]
4. Lorenz KA, Asch SM, Yano EM, Wang M, Rubenstein LV. Comparing strategies for United States veterans' mortality ascertainment. Popul Health Metr. 2005 Feb 24;3(1):2. PMID: [Abstract]
5. ISI Web of Knowledge, Accessed January 2006. Available: http://isi01.isiknowledge.com/portal.cgi/wos/.