US: Focus on years of life lost rather than cause of death to understand mortality trends

The research published this month in the American Journal of Public Health calculated years of life lost to the top 15 causes of death in the US between 1995 and 2015 (examining more than two million death certificates each year), compared this to the number of deaths and examined reasons for differences.

“Focusing on life-years provides perspective on the societal burden of disease and highlights the disparities in disease burden,” said Glen Taksler, Cleveland Clinic researcher and lead author of the study. “Reordering mortality by life-years lost paints a more complete picture of changing mortality and its distribution across various populations.”

As an example, researchers concluded that, although heart disease is the leading cause-of-death overall, other conditions, such as cancer, caused more life-years lost.

In 2015, heart disease caused 6 per cent more deaths than cancer - 635,310 compared to 596,730 - but cancer caused 23 per cent more life-years lost - 9,260,413 for cancer compared to 7,529,750 for heart disease - because cancer is more common in young and middle-aged adults.

The analysis also highlights the differential success in treating heart disease and cancer. Improvements in primary and secondary prevention for coronary artery disease, coupled with better acute treatments, have led to a 42 per cent reduction in years of life lost to heart attacks since 1995.

In contrast to the gains in heart disease, years of life lost to cancer increased 16 per cent from 1995 to 2015. This was mostly because of growth in the number of middle-aged Americans. Life-years lost only declined for six types of cancer, highlighting the need to target cures for the least survivable cancers to achieve population-level gains.

Conditions that disproportionately affect young people appeared more prominently when measured by life-years lost. For example, highlighting the growing epidemic of drug overdoses, the entire gains of the past 20 years in preventing and treating HIV were offset by the increase in life-years lost to accidental deaths.

Racial disparities were also studied. Progress in heart disease was mostly limited to whites; life-years lost increased 20.8 percent for black males and 3.5 percent for black females, which the researchers attribute to increased population size and life expectancy for young and middle-aged minorities.

The researchers note life-years lost is not a new concept but has rarely been used to assess long-term mortality trends for all leading causes of death.

“We believe this thinking can best inform policymakers to prioritise research funding and measure progress toward mortality reduction on the basis of disease burden,” Taksler said.

American Journal of Public Health: doi:10.2105/AJPH.2017.303986)