Primary Care Corner with Geoffrey Modest MD: Life Expectancy and Income

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By Dr. Geoffrey Modest

A massive data analysis was done looking at the relationship between income and life expectancy in the US from 2001-2014 (see doi:10.1001/jama.2016.4226).

Details:

  • Income data was from 1.4 billion de-identified tax records from 1999-2014, using pretax household earnings as measure of income. For those not filing a tax return, they looked at the sum of all wage earnings (W-2 forms) plus unemployment benefits. Income was adjusted to 2012 dollars
  • Mortality data from Social Security Administration tax records.
  • Assessed life expectancy at 40 years of age by household income percentile, sex, geographical area.
  • Evaluated 1,408,287,218 person-year observations for people aged 40-76. Mean age 53. mean household earnings $61,175/yr
  • For people under 63 yo, mortality rates were calculated based on income percentile 2 years earlier (they chose 63 yo, since income rates after age 61 correlate less well with earlier earnings). They used models to estimate mortality rates after age 76, and were adjusted for racial/ethnic composition of income groups. local variations of life expectancy were assessed based on zip code of where their income tax returns were mailed

Results:

  • ​Total of 4,114,380 deaths among men ​(mortality rate of 596.3 per 100K); 2,694,808 deaths among women (mortality rate of 375.1 per 100K)
  • Higher income was associated with greater longevity throughout the income distribution, based on the income distribution at age 40
    • Gap in life expectancy between the richest 1% and the poorest 1% was 14.6 years (14.4-14.8) for men and 10.1 years (9.9-10.3) for women
    • Gap between men and women was more pronounced in the bottom 1% [6.0 years (5.9-6.2)] vs in the top 1% [1.5 years (1.3-1.8)]
    • The overall gap was non-linear by $$: going from the 95th to 100th% ($224K to $1.95M annual income) had much smaller gains in life expectancy than going from the 10th to 15th% ($14K to $20K)
  • Inequality in life expectancy increased over time
    • Between 2001 and 2014, life expectancy increased by 2.34 years for men and 2.91 for women in the top 5% of the income distribution, but only 0.32 years for men and 0.04 years for women in the bottom 5% (p<0.001 for both sexes)
  • ​Life expectancy in low-income people varied substantially across local areas. In the bottom income quartile, life expectancy varied by approx 4.5 years between areas with the highest and lowest longevity
    • Changes in life expectancy between 2001 to 2014 ranged from gains of more than 4 years to losses of more than 2 years across areas
    • The variations formed “belts” in their maps of the US: the states with the lowest life expectancy in the bottom income quartile were from Michigan to Kansas (including Ohio, Indiana, Kentucky, Tennessee Arkansas, Oklahoma); the states with the highest were California, New York and Vermont. In terms of the highest income quartile, the lowest life expectancy (<85.3 yrs) were Nevada, Hawaii,and Oklahoma; and the highest life expectancy (>87.6 yrs) was in Utah, Washington DC, and Vermont
    • Also, trends in life expectancy over time varied: greatest increase was in Massachusetts (>0.19 years annually) for those in the bottom income quartile;  and life expectancy decreased (losing > 0.09 years annually) in Alaska, Iowa and Wyoming
  • Local geographical differences in life expectancy in the lowest income quartile were significantly correlated with health behaviors (e.g., negatively with smoking, r=-0.69, p<0.001 and obesity, r=-0.47, p<0.001; but positively with exercise rates, r=0.32, p=0.004), but not with access to medical care for the lowest income group (assessing health insurance spending, quality of primary care), physical environmental factors (air pollution, lack of access to healthy food; though of note, there was almost statistically significant differences between rich and poor life expectancy in those areas with the most residential segregation), income inequality/social cohesion (income inequality seems to be within income groupings, but they also looked at % religious, % Black), or labor market conditions (unemployment rates, changes in population, changes in size of labor force).
    • Life expectancy for low-income people was positively correlated with the local fraction of immigrants (r=0.72, p<0.001), median home values (r=0.66, p<0.001), fraction of college graduates (r=0.42, p<0.001), population density (r=0.48, p<0.001) and local per-capita government expenditures (r=0.57, p<0.001)
    • Life expectancy for high-income people was less variable, but notable for exercise rates (r=0.46, p<0.001); negatively correlated with Medicare expenditures (r=-0.55, p<0.001) but positively with index of preventive care (r=0.55, p<0.001)
    • Data from the National Center for Health Statistics (NCHS) show that the majority of the variations in those with low SES are related to medical causes (heart disease, cancer) vs external causes (accidents, suicide, homicide)

A few perspective issues:

  • ​As a point of international reference, the life expectancy for men in the bottom 1% income in the US is similar to the mean life expectancy for men in Sudan and Pakistan; men in the top 1% in the US have higher life expectancy than the mean for any other country
  • As an internal point of reference, the 10-year gap in life expectancy between the top and bottom 1% in the US is equivalent to the decrement in life expectancy attributable to lifetime smoking
  • ​From NCHS statistics, the difference in the improved life expectancy for the rich over the poor (around 3 years, in comparing top and bottom 5%) is equivalent to the increase in life expectancy at birth if all cancer deaths were eliminated (3.2 years)

So, some points:

  • This is a quick and dirty, but large and powerful study which gets into some of the details of health inequalities in the US.  The measurements of income, based on tax returns mostly, is undoubtedly missing much, especially from the low income group (typically still very low incomes but from under-the-table jobs, unreported income by undocumented workers, etc.) and from very high income group (offshore shell companies, legal and illegal shenanigans to hide income). Also, the mortality rates in those >76 yo is based on mathematical modeling/estimates. And some of the health outcome differences between the income groups is no doubt affected by local circumstances (even the rich in some areas are exposed to the same environmental exposures as the poor, perhaps some of the same food quality, cultural issues such as types of food eaten or priority to do exercise, or access to the highest tech medical care). Some support for this last argument is that the poor do better if living in areas of higher education and more affluence (higher median home values, etc.), which may represent certain local cultural values, such as less smoking (and, in our poorer communities in Boston, there is clearly less smoking, for example, than in many other areas of the country). Also, the finding that the trend in communities with more geographical separation to have more longevity differences also supports that the more isolation of the different income communities from each other tends to make the longevity lines clearer.
  • Perhaps some of the most poignant and socially-relevant findings are:
    • The gaps are increasing, with some of the poorer communities experiencing a decrease in life expectancy
    • ​One other inequity (noted in other blogs) is the regressive nature of our Social Security system: the rich live longer, so get social security payments for a longer time
    • Although just reading numbers sometimes makes it hard to really understand the impact of the differences, the comments about equivalency of these differences with lifetime smoking or zero deaths from cancer really put this in perspective
    • Also, the international perspective I think is quite useful. again, the US does quite poorly overall in life expectancy, except for the very wealthy, and, per several other blogs (see below), this really does correlate with our remarkably poor social systems (or even “safety nets”) as compared to essentially every other westernized, resource-rich country (as noted in the blog below, the book The American Health Care Paradoxshows quite well that we spend huge amounts on “health care”, but unlike other countries, the vast majority of this is for medical care instead of social or public health programs that promote public health). It is telling in the above JAMA study that longevity was associated with local governmental expenditures, which may reflect more social or public health programs
  • I am pretty surprised that access to care was not so related to life expectancy. Not sure how to explain that, since so much literature has come out, for example, about cancer or heart disease outcome differences by income or by race/ethnicity. One interesting finding was that Medicare coverage at age 65 did not affect longevity, and one might think that there would be improved health care access when getting Medicare; though I certainly see many patients who do not qualify for Medicare (did not work the 40 quarters, or were undocumented workers who may have worked 2 jobs for way more than 40 quarters…). Perhaps some of the issue is that they really only looked at income and did not do a detailed analysis by race/ethnicity (many of their analyses did include race- and ethnicity-adjusted life expectancy, but I’m not really sure what that means, and they did not breakdown any of the more specific data above by these important demographics).

See https://stg-blogs.bmj.com/bmjebmspotlight/2016/02/24/primary-care-corner-with-geoffrey-modest-md-increasing-disparities-in-life-expectancy/​ which goes into detail about the increasing life expectancy disparity paralleling income disparity, with a pretty long list of comments, which I will not repeat here, which also includes an article on mortality in younger people, finding a much higher mortality in the US than in other countries.

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