Disability Disparities May Be Explained by Obesity, Smoking, Physical Labor
New research from Tarlise Townsend
Excess body mass, smoking and manual labor explain a large proportion of disability
disparities in the United States, according to a new University of Michigan study.
While it's well documented that those with less education, and especially those without
a high school diploma, are more likely to become disabled, less is known about the
mechanisms behind that link, University of Michigan researchers say.
"We know that smoking, obesity and manual labor are heavily shaped by educational
attainment, and that they in turn increase the risk of disability," said lead author
Tarlise Townsend, who conducted the work while a doctoral student at the University
of Michigan School of Public Health.
"So we wanted to know at the U.S. population level, how much of the educational disparities
in disability are explained by those three factors? We wanted to better understand
the pathways by which education 'gets under the skin' to influence disability risk."
Townsend and colleagues found that those three factors accounted for 60% of educational
disparities in disability in younger women (65 and younger), 65%-70% in younger men,
40% in older women and 20%-60% in older men.
They followed more than 3,000 individuals at risk for disability from 2003 to 2015
by using data from the nationally representative Panel Study of Income Dynamics—the
longest running longitudinal household survey in the world—housed at the University
of Michigan Institute for Social Research.
To define disability, the researchers utilized a standard set of survey indicators
that ask about people's ability to carry out everyday life activities such as bathing
or showering, preparing meals and doing heavy housework.
While previous research looked at prevalence of disability, which provides a snapshot
of who has a disability at a given time, the University of Michigan study increased
methodological rigor by looking at incidence, or the switch from not having a disability
to having a disability.
"Then we said, 'OK, what is the role of these three factors in explaining educational
disparities in disability?" Townsend said. "If, for example, nobody had smoked in
the population, how much smaller would the disability gap be? If nobody were overweight
or obese in the population, how much smaller would the disability gap be?
"That allowed us to estimate how much of the disability gap in the U.S. population
is explained by those risk factors, versus how much of it has to be explained by other
mechanisms."
The researchers found that smoking and manual labor were the main drivers of disparities
in disability in men under 65. Whereas for both younger and older women, the main
driver was overweight and obesity.
"If we want to reduce disparities in disability, we need to understand the mechanisms
by which educational attainment translates into disability," Townsend said. "It's
crucial to remember that changing these risk factors requires much more than individual-level
volition.
"These behaviors, as well as the type of work people do, are shaped by a range of
powerful societal forces. If we want to reduce disparities in disability, we need
to think hard about how we can both improve educational attainment and 'unlink' education
from these risk factors: occupational opportunity, obesity and smoking."
For a long time, disability seemed to be falling in the American population, but that
trend ended in the early 2000s, Townsend said. Now, Americans are becoming disabled
at younger ages, and educational disparities in disability seem to be growing.
"We don't understand why disability levels in the U.S. have plateaued and why disparities
in disability by educational attainment are so large," said co-author Neil Mehta,
assistant professor of Health Management and Policy at the University of Michigan
School of Public Health. "Our study helps shed some light in understanding these troubling
patterns."
The study is published in the Journal of Gerontology Social Sciences.