How Much Height We Lose as We Age is Key Indicator
of Health, Mental Issues
High school grads shrink less that illiterate;
strong relationship between height loss and cognitive health found;
health habits as adults influence how much we shrink
April 1, 2013 – A large study of older adults,
which claims to be the first to examine height loss as we age, finds
that choices we make throughout life impact how much we shrink as senior
citizens. For example, High school grads shrink nearly 2 cm less than
The study by economists from the University of
Southern California, Harvard University and Peking University used
unique data from a new massive longitudinal survey of 17,708 adults
beginning at age 45. The researchers show for the first time that
lifestyle choices we make in adulthood - and not just the hand we're
dealt as children - influence how tall we stand as we age.
"Had we only examined the correlations between
measured height and health, we would have missed this important
insight," said John Strauss, professor of economics at USC, and an
investigator on a study published in the April 2013 issue of the
American Economic Journal: Applied Economics.
"The evidence shows that it is not only early-life
events that are associated with how we age, but health decisions in
later life as well."
While prior work has looked for the connection
between height and health — both in childhood and adulthood — the
researchers are the first to examine height loss as we age. They show
that regardless of your maximum height, the loss of height over time is
also an important indicator for other health issues as we age.
For example, the research reveals an especially
strong relationship between height loss and cognitive health. Those who
had lost more height were also much more likely to perform poorly on
standard tests of cognitive health such as short-term memory, ability to
perform basic arithmetic and awareness of the date.
Among the socioeconomic factors that correlate to
height loss, urban dwellers had much less height loss than those in
rural areas, the researchers found, in a country where there has been
significant migration to urban areas in the last few decades.
In addition, having completed primary school,
rather than being illiterate, is associated with 0.9 cm less height
shrinkage in men - a large difference when considering that overall
average height loss for men is 3.3 cm. Completing high school meant an
additional 1 cm less in shrinkage.
For women, having completed primary school was the
difference in 0.6 cm of shrinkage, compared to average overall height
decrease of 3.8 cm.
"Height has been recognized as an acceptable proxy
for childhood health conditions, but there are complications there,"
says USC economist Geert Ridder, a co-investigator on the study.
"Some of adult health might be determined by
childhood circumstances, but people shrink differentially, and that
shrinkage is also a measure of adult health conditions."
All humans go through physical changes with age,
including an increase in body fat and decrease in bone mass. But a
decrease in height can be further exacerbated by certain kinds of
arthritis, inflammation of spine joints or osteoporosis, which other
studies have shown are associated with such lifestyle choices as diet,
exercise and smoking.
The researchers used new data from the China Health
and Retirement Longitudinal Study, a groundbreaking sampling project led
by USC economist Strauss, Yaohui Zhao of the China Center for Economic
Research (CCER) at Peking University and Gonghuan Yang of the Chinese
Academy of Medical Sciences and Peking Union Medical College, that
covers 150 counties randomly chosen throughout China.
The baseline for the survey was collected from June
2011 to March 2012 and includes both subjective self-reported responses
to survey questions as well as objective physical measurements such as
These physical measurements and personal interviews
will be followed-up with the same 17,708 people every two years —
capturing, for the first time, critical data about human aging in the
most populous and most rapidly aging country in the world.
For example, recent changes in social security
policy and health insurance in China provide a valuable opportunity for
researchers to study how health care actually affects health and aging
in a large population, with insights for other developing health care
systems worldwide, as well as an opportunity to identify possible
under-diagnosis of various chronic conditions.
The researchers will also be able to examine the
role specific historical events in China may have had on long-term
health, including whether there are health and aging differences among
those who were "sent-down" during the Cultural Revolution.
The research is supported by the National Institute
of Aging, the China Natural Science Foundation, the Fogarty
International Center of the National Institutes of Health and the World
To estimate full adult height for older study
participants, the researchers examined relationships between current
height and the length of limbs, which do not shrink with age, from
younger survey participants who have not yet started shrinking.
Wei Huang, a graduate student in economics at
Harvard University, and Zhao and Xiaoyan Lei of Peking University were
co-authors of the study.
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