Potential Years of Life Lost (PYLL)

Sex and Gender-based Analysis of this topic

Definition

Potential years of life lost (PPYL) is a measure of the relative impact of various disease and lethal forces on society [1]. PYLL highlights the loss to society as a result of youthful or early deaths. The figure for potential years of life lost due to a particular cause is the sum, over all persons dying from that cause, of the years that these persons would have lived had they experienced normal life expectation (typically 75 years for Canadian calculations) [2]. For example, if a person dies at age 55, the result is 20 PYLL. By summing PYLL across a population, it is possible to estimate the impact of specific causes of death in terms of years of life lost. PYLL is typically expressed as a standardized rate per 100,000 population. In 2001, Canadian PYLL was estimated to be 5101.5 per 100,000, with sex-specific rates of 3863 for women and 6328 for men [3]. As the calculation of PYLL takes age at death into account, it places a higher weight on mortality among the younger age groups than among older age groups than standard mortality rates [5].

 
 
Sex Issues

Although men have a higher PYLL across all causes, when only sex-specific causes of death are examined (including such causes as complications of pregnancy, cancers of the reproductive system, perinatal death), PYLL among women is approximately four times higher than among men [4]. There are also differences between the sexes in the predominant causes of PYLL. For example, cancers are responsible for the most PYLL for women, followed by injuries and cardiovascular disease [6]. Among men, injury is responsible for the most PYLL, followed by cancer and cardiovascular disease.

 
 
Gender Issues

As can be seen above, a large portion of the sex difference in overall PYLL can be explained by external, non-biological causes that are higher for men than women, particularly at younger ages. These include higher mortality risks from preventable causes, such as accidents, poisonings, and non-domestic violence [4]. Gender roles, especially the association between masculinity and risk-taking behaviour, create higher risks for men.

Smoking has been linked to a number of the top causes of mortality including lung cancer, acute myocardial infarction, and chronic obstructive pulmonary disease (COPD). Sex-specific trends in smoking show that historically, men have always smoked more than women. However, smoking rates have been converging in recent years. According to data from the 2007 Canadian Tobacco Use Monitoring Survey, for youth in grades 10-12, 47% of females report having tried cigarettes compared to 49.5% of males [7]. The effects of higher rates of female smoking can be seen in the fact that the largest specific cause of PYLL for women is lung cancer, which surpassed PYLL from breast cancer in the last decade [4].

 
 
Diversity

Specific analysis of PYLL among various cultural groups is not readily available, but subpopulation trends in life expectancy and mortality can provide an indication of groups who are more likely to experience greater PYLL. Geographically speaking, women who live in rural and remote areas of Canada have considerably shorter life expectancies and higher mortality rates than women in the rest of Canada [4]. Life expectancies for Aboriginal women are shorter than their non-Aboriginal counterparts. One study found that on-reserve First Nations women had a life expectancy that was on average 8 years shorter than non-First Nations women in Manitoba [8]. Mortality rates are also higher for people with low socio-economic status compared to those with high socio-economic status, regardless of whether status was determined by education, occupation, or income [9].

 
 
Critique

Mortality metrics, including PYLL, are useful lenses through which to analyze the overall health of the Canadian population. PYLL provides pertinent information concerning sex- and gender-specific causes of mortality, which can guide healthcare policy and programs aimed at the population health level. However, PYLL also has some notable shortcomings. PYLL does not take quality of life into account, or in other words, does not adjust for levels of disability associated with years of life lived. Additionally, PYLL is often calculated without discounting future years lived, so that the value of a year of life lived immediately is equal to that of a year of life lived many years in the future. Finally, because PYLL is based on mortality data, it is often limited with respect to diversity and inequity information, unless mortality data is linked with Census data.

NOTE: PYLL is affected by any mortality-causing agent, including accidents, disease, or genetic factors. Any mortality-related data source will be applicable to PYLL studies, including cancer, cardiovascular disease, and many others.

 
 
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