Mortality Inequality Shrinks for Young Americans

Ricki Lewis, PhD

April 21, 2016

Mortality inequality declined significantly among people aged 30 years and younger in the past 3 decades in the United States, according to a study published online April 21 in Science. Mortality inequality continued to increase among older adults during the same period.

"Our results point to decreasing inequality in mortality, particularly among the younger cohorts who will form the future adult and elderly population of the United States," write Janet Currie, PhD, from Princeton University in New Jersey, and Hannes Schwandt, PhD, from the Institute for the Study of Labor in Bonn, Germany.

The improvements could be the effect of more even distribution of health and healthcare, they note. "In at least one important example, the case of expansions of public health insurance for poor infants and young children in the late 1980s and early 1990s, the reduced early death rates in these cohorts are associated with better health and higher earnings as these cohorts reach young adulthood. Thus there appears good reason to hope that today's young will also be healthier when they reach old age and that inequality in mortality will decrease among these elderly in the future."

Several studies during the last 2 decades have shown increased mortality among poorer people, with some investigators suggesting that the gap is widening and that overall life expectancy is falling among the poor. However, Dr Currie and Dr Schwandt point out that most analyses of life expectancy focus on people older than 40 years or follow life expectancy from birth without accounting for changing socioeconomic factors. In addition, analyses of children and adolescents have been lacking.

To fill that knowledge gap, the investigators used county-level data to analyze mortality in 1990, 2000, and 2010 in the United States by income level. They ranked all counties by poverty level and grouped them into 20 bins according to wealth, with each bin representing about 5% of the overall US population. The approach enabled comparisons between poverty level and mortality in different age groups over time. For any of the three times, the researchers could point to a poorest group of counties and a richest group, although the exact counties with these designations may have changed.

The study considered 21,175,011 deaths as 3-year mortality rates for Census years 1990, 2000, and 2010. Socioeconomic county characteristics (poverty rate, median and per capita income, percentage of high school dropouts) came from the Census in 1990 and 2000 and from the 2008 to 2012 American Community Survey for 2010. The disparity is large, with 30.47% living in poverty in 1990 for the poorest counties and 28.30% in poverty for 2010 compared with 3.75% in 1990 and 5.58% in 2010 for the most economically well-off counties.

The researchers note that analyzing overall life expectancy at birth for the three periods "masks considerable heterogeneity in trends in mortality rates at different ages." Whereas, using their age-specific approach, they found that 3-year mortality rates for male newborns decreased by 4.2 per 1000 (going from 9.77 to 5.53) in the richest counties from 1990 to 2010, but decreased by 8.49 deaths per 1000 (going from 18.28 to 9.79) in the poorest counties.

The researchers saw a similar decline in mortality inequality for males up to age 20 years, after which the inequality decreased somewhat until age 50 years, but no significant difference was seen from ages 50 to 75 years. After age 75 years, the mortality inequality increased significantly among men.

Mortality among females also fell until age 19 years, with greater improvements in the poorest counties. The improvements in mortality inequality continued, but at a slower rate, until age 30 years, but then showed no improvement for women aged 30 through 45 years. For women older than 45 years, mortality inequality increased during the study period.

The researchers conclude, "Our analysis of these rates indicates that inequality in mortality between rich and poor counties has strongly declined among infants, children and young adults up to age 30 of either gender as well as among adult males up to age 50. Among older adults, mortality has continued to decline, though declines are generally greatest in the richest counties, indicating increasing inequality in mortality, which is in line with the literature that has focused on inequality trends at older ages."

The researchers list possible explanations for the closing disparity among the young: better air quality, less smoking, early education programs, and expansion of health insurance.

A limitation of the study design is not accounting for possible changing demographics of counties over time.

The authors have disclosed no relevant financial relationships.

Science. Published online April 21, 2016. Full text

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