Premature Death
What Is It?
The County Health Rankings seeks to quantify and compare the health status of county populations by measuring the burden of premature deaths (premature mortality), an important measure of a population’s well-being. Premature deaths are deaths that occur before a person reaches an expected age, e.g., age 75. Many of these deaths are considered to be preventable.
Why Do We Measure It?
Measuring premature mortality, rather than overall mortality, underlies the intent of the County Health Rankings to focus attention on deaths that could have been prevented.[1] By examining premature mortality rates across communities and investigating the underlying causes of high rates of premature death, resources can be targeted toward strategies that will extend years of life.
Measurement Strategies
Vila et al. provides a comprehensive summary of the various methods that can be used to quantify death rates, including the crude death rate, age-specific death rates, age-adjusted death rates, years of potential life lost and others. Because there is no one best measure that captures all aspects of mortality, a judgment must be made based on which dimension of mortality is most useful for a particular application.[1] Different strategies, such as age-adjustment, may also be employed to facilitate comparisons across populations with different characteristics.
In contrast to more traditional death rates, Years of Potential Life Lost (YPLL) emphasizes the processes underlying premature mortality in a population.[3] The concept behind YPLL involves using the number of years of life (life-years) lost due to premature death, defined by a standard cut-off age in a population, to obtain a total sum of the life-years lost before ages 65, 75, or 85 (for example). Dranger and Remington provide a more detailed description of the YPLL calculation methodology.[4] As with age-adjusted death rates, it is possible to calculate age-adjusted YPLL rates using a standard population to make the measure comparable among populations.[4] There is debate over how “premature” death is defined and which age – 65, 75, or 85 – is most appropriate to use as the upper age limit for calculating YPLL.
Although YPLL and age-adjusted death rates are the most commonly used measures, other measures have been proposed that take a different approach. Vila et al. provides more information about these other measures:
- Potential gains in life expectancy (PGLE)
- Cumulative rate of potential life lost (CRPLL)[1]
Finally, while the other mortality measures discussed are ways of quantifying and presenting death rates in alternative ways, the life expectancy measure can be thought of as an inverse measure of death, or a measure of how long a population is surviving on average. Since life expectancy changes with age and with time, life expectancy calculations are more complex than those required for calculated YPLL.[4]
What Is the County Health Rankings Measurement Strategy?
The County Health Rankings reports YPLL as its measure of premature death based on all deaths occurring before the age of 75. Each of these deaths contributes to the total number of years of potential life lost. For example, a person dying at age 50 would contribute 25 years of life to the YPLL index. The YPLL is age-adjusted to the 2000 U.S. population to allow comparison between counties and is reported as a rate per 100,000 people. Three-year averages are used to create more robust estimates of mortality, particularly for counties with smaller populations. YPLL rates are calculated from data in the National Vital Statistics System and are provided by the CDC’s National Center for Health Statistics.
Measure Strengths & Limitations
YPLL is a widely used measure of the rate and distribution of premature mortality. The measure was introduced mainly because simple mortality rates do not fully address the issue of premature death, the impact of disease and death, and its cost to society.[5] Reduction in YPLL is an important public health goal.[6]
YPLL emphasizes deaths of younger persons, whereas statistics that include all mortality and not just premature mortality are dominated by deaths of the elderly.[7] Including all mortality would have a significant impact on the County Health Rankings and may draw attention to areas with higher mortality rates among the oldest segment of the population, where there may be little that can be done to change chronic health problems that have developed over many years.[1]
YPLL is often used to determine the burden of premature death due to a particular cause within a population, but it can also be effectively used to distinguish the burden of premature death in populations.[4]
YPLL is not without weaknesses. The measure can be difficult for lay people and public health practitioners to interpret.[4] For example, the Epidemiology Bureau in Florida investigated this issue and learned that county Public Health Units often did not understand how to interpret YPLL.[8]
YPLL weights deaths that occur at younger ages more heavily than deaths at older ages. For example, using YPLL-75, a death at age 55 counts twice as much as a death at age 65, and a death at age 35 counts eight times as much as a death at age 70.[4] Further, deaths that occur after the age limit are not accounted for at all. Because of this, YPLL can fail to completely capture the burden of chronic disease, especially if the age cut-off is set too low.[4]
References
[1] Vila PM, Booske BC, Remington PL. Measuring Mortality in the Wisconsin County Health Rankings. Madison, WI: University of Wisconsin Population Health Institute; 2006. Technical Report.
[2] Gordis L. Epidemiology. Philadelphia, PA: Elsevier Saunders; 2004.
[3] Arca M, Diorio F, Forastiere F, Tasco C, Perucci CA. Years of potential life lost (YPLL) before age 65 in Italy. Am J Public Health. 1988;78:1202-1205.
[4] Dranger E, Remington P. YPLL: A Summary Measure of Premature Mortality Used in Measuring the Health of Communities. Madison, WI: University of Wisconsin Population Health Institute;2004. Issue Brief 5(7).
[5] Lee WC. The meaning and use of the cumulative rate of potential life lost. Int J Epidemiol. 1998;27:1053-1056.
[6] Gardner JW, Sanborn JS. Years of potential life lost (YPLL)-what does it measure? Epidemiology. 1990;1:322-329.
[7] Centers for Disease Control and Prevention. Premature mortality in the United States: Public health issues in the use of years of potential life lost. MMWR Morb Mortal Wkly Rep. 1986;35(suppl 2):1S-11S.
[8] McDonnell S, Vossberg K, Hopkins RS, Mittan B. Using YPLL in health planning. Public Health Rep. 1998;113:55-61.
