What can lifespan variation reveal that life expectancy hides? Comparison of five high-income countries.

OBJECTIVES: In most countries, life expectancy at birth (e0) has improved for many decades. Recently, however, progress has stalled in the UK and Canada, and reversed in the USA. Lifespan variation, a complementary measure of mortality, increased a few years before the reversal in the USA. To assess whether this measure offers additional meaningful insights, we examine what happened in four other high-income countries with differing life expectancy trends. DESIGN: We calculated life disparity (a specific measure of lifespan variation) in five countries -- USA, UK, France, Japan and Canada -- using sex- and age specific mortality rates from the Human Mortality Database from 1975 to 2017 for ages 0--100 years. We then examined trends in age-specific mortality to identify the age groups contributing to these changes. SETTING: USA, UK, France, Japan and Canada. PARTICIPANTS: aggregate population data of the above nations. MAIN OUTCOME MEASURES: Life expectancy at birth, life disparity and age-specific mortality. RESULTS: The stalls and falls in life expectancy, for both males and females, seen in the UK, USA and Canada coincided with rising life disparity. These changes may be driven by worsening mortality in middle-age (such as at age 40). France and Japan, in contrast, continue on previous trajectories. CONCLUSIONS: Life disparity is an additional summary measure of population health providing information beyond that signalled by life expectancy at birth alone.