Why should you care about the distribution of deaths?

Cristian Newman (Unsplash)

Would you rather live in a society where everyone dies at the age of 80 or in a society where half of the population dies at 40 and the other half at 120? Interestingly, both of these societies have the same life expectancy: 80. Life expectancy is the average age at death. It tells us nothing about the distribution of deaths across ages. But many of us care about that distribution.

In Europe and North America, life expectancy increased rapidly from the beginning of the 19th century mostly due to falling infant and child mortality rates, which resulted in a shift of the distribution of deaths as they became more and more centered around older ages. Rising life expectancy thus coincided with declining inequality in age at death. However, since the second half of the 20th century, most improvements in life expectancy have been due to decreases in mortality rates at older ages. As a result, inequality in ages at which people die has increased in some countries, including the United States (US).

Our study

What can be concluded about changes in population health when increasing life expectancy is accompanied by increasing inequality in the ages at which people die? We tackle this question in our ongoing research.

In short, we propose a methodology to evaluate changes in the distribution of deaths across ages on the basis of a set of moral principles. We start from a principle that is expected to command universal support: a longer life is always preferred to a shorter one. If this is insufficient to find the preferred distribution of deaths over ages, then we move to a more demanding principle: a death at an older age is preferred to a death at a younger age.

We apply the method to 1999-2017 life table data from the US to determine whether the distribution of mortality improved or deteriorated over this period given the postulated moral principles. We find that while the distribution was improving over most of the period, it has deteriorated since 2015. Indeed, since 2015, mortality has continued to decline at older ages (around 80), but these improvements do not outweigh increases in midlife mortality (ages 30 to 70). However, we also note improvements in the distribution of deaths across ages for women and for the black population in 2017 compared to 2016. These improvements are most likely driven by black women.

Implications: what now?

Our method uses standard life table data and so can be applied in most countries over many periods or to make comparisons between countries. It offers the potential to move away from focus on the average age-at-death (life expectancy) towards an evaluation of population health that is sensitive to inequality in the ages at which people die. It could be used to evaluate how specific causes of death impact the distribution of deaths across ages.

PhD student

Jawa Issa

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