In a novel study of health disparities in the
United States, Stanford University School of Medicine researchers have
identified 22 socioeconomic and environmental variables that together are
better indicators of early death than are race or geography. The findings upend
long-held beliefs that where you live and the color of your skin are the best
markers for how long you may live.
The
innovative analysis shows that when factors related to local social conditions
— including education, income and job — are controlled for, health differences
based on being black or white, urban or rural, virtually disappear.
The
study, which will be published online April 17 in PLoS ONE,
examined data about the probability of survival to age 70 for every county of
sufficient size in the nation, classified by sex and race. It then considered
how a number of other factors affect those premature mortality results.
"Geographic
and racial disparities," said first author Mark Cullen, MD, "are best
understood as related to disparities in education, occupations and the like,
which are strongly associated with outcomes in every county we studied, whether
it was large, small, urban, rural, Southern or not."
Cullen,
professor of medicine and chief of the Division of General Medical Disciplines,
added: "While there is an enormous survival difference between some
counties and others, it is the social and environmental characteristics of a
given county and its population that matter the most."
Large
differences in life
expectancy have been documented between different regions of the
country. There is, for example, higher mortality in big urban areas and in the
South. A 2011 study in Population Health Metrics showed that in five counties
in Mississippi, men can expect to live to an average age of 66.5, which is
several years less than the nationwide average.
Racial
disparities in life expectancy are also well-established; adding to the
evidence was a recent UCLA study in Health Services Research showing that
"white males live about seven years longer on average than
African-American men, and that white women live more than five years longer
than their black counterparts."
For
their work, Cullen and his colleagues wanted to present an alternative outcome
to the commonly used life expectancy measurement and look instead at premature
mortality because it more clearly focuses on factors in health during the prime
of people's working lives. Using national data sources for the years 1999-2001,
they examined the probability of survival to age 70 for each sex-race group by
county. (They restricted the study to two races: black and white.)
Not
surprisingly, the paper reports wide variation from county to county as well as
"the chasmic difference between blacks and whites, true for both
sexes." While confirming this racial divide, the researchers made the
startling finding that the counties with the best survival numbers for blacks
had rates that were only a little higher than those in the worst counties for
whites. And they also found that 82 percent of white females born today could
expect to live until age 70 as compared with 54 percent of black males. The
latter comparison is one that hasn't been shown before, Cullen said, and
demonstrates how black men are dying so much more often in their 40s, 50s and
60s.
The
researchers next examined the effect of 22 socioeconomic and environmental variables
on the survival-to-age-70 figures in each race/sex group. They found that
factors such as education, income, job and marital status account for most of
the differences between the various groups.
Cullen
explained, "Once certain factors — such as the fraction of adults in the
county who finish high school, the fraction with managerial or professional
jobs and the fraction of adults who live in two-parent households — are
accounted for, even geography,
such as being in the South, is moot."
It's
not where the county is located that is important. "It's the socioeconomic
variables that turn out to be so predictive," Cullen said. "In a
region where education status is incredibly low, jobs and family structure are
terrible, and there is no wealth, people's health is not going to be
good."
As a
way of testing their findings, the team ran a separate analysis to see what
would happen if the 22 variables were equal among black and whites — for
example, if they had the same level of education and the same mix of managerial
and professional jobs. "Amazingly, almost all of the projected mortality
differences evaporate," said Cullen. "In this hypothetical
experiment, the chances of survival until 70 would be almost identical for
whites and blacks."
As for
future research, Cullen said he and his colleagues want to better understand
why the experience of black men in particular is so abysmal. Some of the policy
changes that would benefit them, such as improvements in the education system
and stronger support to keep families together, are long-term and will take
generations to fix, he said, so the team wants to identify things that could be
changed in the short term.
Cullen
said he is also interested in exploring the resilience of women and what it is
about their biology and lifestyle that makes them so much more likely than men
to live to age 70.
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