Life expectancy and disparity: an international comparison of life table data

Abstract

Objectives: To determine the contribution of progress in averting premature deaths to the increase in life expectancy and the decline in lifespan variation.

Design: International comparison of national life table data from the Human Mortality Database.

Setting: 40 developed countries and regions, 1840-2009.

Population: Men and women of all ages.

Main outcome measure: We use two summary measures of mortality: life expectancy and life disparity. Life disparity is a measure of how much lifespans differ among individuals. We define a death as premature if postponing it to a later age would decrease life disparity.

Results: In 89 of the 170 years from 1840 to 2009, the country with the highest male life expectancy also had the lowest male life disparity. This was true in 86 years for female life expectancy and disparity. In all years, the top several life expectancy leaders were also the top life disparity leaders. Although only 38% of deaths were premature, fully 84% of the increase in life expectancy resulted from averting premature deaths. The reduction in life disparity resulted from reductions in early-life disparity, that is, disparity caused by premature deaths; late-life disparity levels remained roughly constant.

Conclusions: The countries that have been the most successful in averting premature deaths have consistently been the life expectancy leaders. Greater longevity and greater equality of individuals' lifespans are not incompatible goals. Countries can achieve both by reducing premature deaths.

Figure 1

The association between life disparity in a specific year and life expectancy in that year for males in 40 countries and regions, 1840–2009 (see online supplementary table 1). The correlation coefficient between them is 0.77 (95% CI 0.76 to 0.78). The black triangle represents the USA in 2007; the USA had a male life expectancy 3.78 years lower than the international record in 2007 and a life disparity 2.8 years greater. The brown points denote years after 1950, the orange points 1900–1949 and the yellow points 1840–1900. The light blue triangles represent countries with the lowest life disparity but with a life expectancy below the international record in the specific year; the dark blue triangles indicate the life expectancy leaders in a given year, with life disparities greater than the most egalitarian country in that year. The black point at (0,0) marks countries with the lowest life disparity and the highest life expectancy. During the 170 years from 1840 to 2009, 89 holders of record life expectancy also enjoyed the lowest life disparity. The equivalent figure for females is presented in online supplementary figure 2.

Figure 2

The relationship between total life disparity (red), early-life disparity up to the threshold age (blue) and late-life disparity after the threshold age (green). The darkest hues relate to data from 1950–2009, middle hues 1900–1949 and lightest hues 1840–1899. Total disparity is an additive function of early-life disparity and late-life disparity. Since 1840 the decrease in total life disparity has resulted from reductions in early-life disparity. The correlation coefficient between early-life disparity and total life disparity is 0.997 (95% CI 0.997 to 0.997). Late-life disparity has remained remarkably constant at about 5 years across a wide range of life expectancies. Hence, according to this measure, there has been neither a marked compression nor expansion of mortality at advanced ages as life expectancy has increased. Data are for females from the 40 countries and regions of the Human Mortality Database (see online supplementary table 1).

Figure 3

The relationship between remaining life expectancy at age 15 (e₁₅) and life disparity at age 15, according to the year in which e₁₅ was first reached. Up until 1960 and for e₁₅ from 54 to 59, the pioneers in first attaining a level of remaining life expectancy did so with higher levels of life disparity than the laggards. Since 1960 and at higher remaining life expectancies, the relationships between remaining life expectancy and life disparity at age 15 are not correlated. Ages 15 and over were examined to make the results comparable to those obtained by Smits and Monden.⁵ Data are for females from the 40 countries and regions in the Human Mortality Database (see supplementary online table 1)