Women who maintain a healthy weight and who have lower perceived stress may be
less likely to have chromosome changes associated with aging than obese and
stressed women, according to a pilot study that was part of the Sister Study.
The long-term Sister Study is looking at the environmental and genetic characteristics
of women whose sister had breast cancer to identify factors associated with
developing breast cancer. This early pilot used baseline questionnaires and
samples provided by participants when they joined the Sister Study.
Two recent papers published in Cancer Epidemiology Biomarkers and
Prevention looked at the length of telomeres, or the repeating DNA
sequences that cap the ends of a person’s chromosomes. Telomere length
is one of the many measures being looked at in the Sister Study.
Telomeres protect the ends of chromosomes and buffer them against the
loss of important genes during cell replication. Over the course of an
individual's lifetime, telomeres shorten, gradually becoming so short
that they can trigger cell death. The papers show that factors such as
obesity and perceived stress may shorten telomeres and accelerate the
"Together these two studies reinforce the need to start a healthy
lifestyle early and maintain it," said Linda Birnbaum, Ph.D., the
director of the National Institute of Environmental Health Sciences
(NIEHS), part of the National Institutes of Health. The researchers who
published these papers are from the NIEHS which sponsors the Sister
The papers are the first findings coming out of the Sister Study.
The Sister Study is just completing its enrollment of 50,000 women aged
35-74 to prospectively study risk factors for breast cancer. "We
anticipate a wealth of information to come out of the Sister Study,"
said Dale Sandler, Ph.D., chief of the Epidemiology Branch at NIEHS and
principal investigator of the Sister Study. "Not only do we hope to
find out more about the environmental and genetic factors that might
lead to breast cancer, we also want to learn more about how factors
such as stress, diet and exercise might impact cancer and other disease
One of the studies published this week found that women who were
obese for a long time had reduced telomere length. The researchers
looked at the relationship between various measures of current and past
body size and telomere length in 647 women enrolled in the Sister
Study. They found that women who had an overweight or obese body mass
index (BMI) before or during their 30s, and maintained that status
since those years, had shorter telomeres than those who became
overweight or obese after their 30s. "This suggests that duration of
obesity may be more important than weight change per se, although other
measures of overweight and obesity were also important," said Sangmi
Kim, Ph.D., epidemiologist and lead author on the paper. "Our results
support the hypothesis that obesity accelerates the aging process,"
The other paper published in February looked at the association
between telomere length and the perceived stress levels of 647 women
enrolled in the Sister Study, and found that similar to the obesity
finding, stress can also impact telomere length. The researchers
extracted DNA from blood drawn during initial enrollment to estimate
telomere length, and measured levels of stress hormones in urine
samples the women provided. Additionally, the researchers used a
standardized scale to characterize levels of perceived stress based on
answers to questions about how stressful participants perceived their
life situations. In general, the researchers report that women in the
Sister Study typically reported low levels of perceived stress.
"Even so, women who reported above-average stress had somewhat
shorter telomeres, but the difference in telomere length was most
striking when we looked at the relationship between perceived stress
and telomere length among women with the highest levels of stress
hormones," said Christine Parks, Ph.D., an NIEHS epidemiologist and
lead author on the paper. "Among women with both higher perceived
stress and elevated levels of the stress hormone epinephrine, the
difference in telomere length was equivalent to or greater than the
effects of being obese, smoking or 10 years of aging."
The researchers also found that the effects of stress may be stronger in older
women. They found that among women 55 years and older, those with higher perceived
stress had 5 percent shorter telomeres than women with low stress levels. "More
research is needed to determine if the shortening of telomeres in these women
is related to aging or hormonal differences in the stress response, or simply
represents the accumulated effects of stress across the lifespan," said Parks.
"These papers remind us that there are things people can do to
modify their behavior and live healthier lives, such as maintain a
healthy weight and cultivate healthy responses to stress," said
The NIEHS supports research to understand the effects of the
environment on human health and is part of NIH. For more information on
environmental health topics, visit our website at http://www.niehs.nih.gov.
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