Telomeres are long stretches of DNA at the ends of our
chromosomes, which protect our genes from damage or improper regulation.
Telomeres don't last forever. In most of our cells,
telomeres get shorter each time that cell divides. And when they get too
short, the cell either quits dividing or dies.
‘People who had more infections as babies harbor a key marker of cellular aging as young adults: the telomeres are shorter than in adults who were healthier as infants.’
That makes telomere length particularly important for the cells
of our immune system, especially the white blood cells circulating in
our bloodstream. When activated against a pathogen, white blood cells
undergo rapid rounds of cell division to raise a defensive force against
the infectious invader.
But if telomeres in white blood cells are
already too short, the body may struggle to mount an effective immune
Many studies - in laboratory animals and humans - have associated
shorter telomeres with poor health outcomes, especially in adults. But few studies have addressed whether or not events early in a person's life might affect telomere length.
New research indicates that people who had more infections as babies
harbor a key marker of cellular aging as young adults: the protective
stretches of DNA which "cap" the ends of their chromosomes are shorter
than in adults who were healthier as infants.
The findings, published in the American Journal of Human Biology
, shed new light on how the intricate interplay between genetics and environment impacts human health.
"These are important and surprising findings because - generally
speaking - shorter chromosome 'caps' are associated with a higher
burden of disease later in life," said lead author Dan Eisenberg, an
assistant professor of anthropology at the University of Washington.
The 'caps' Eisenberg and his co-authors measured are called telomeres.
Prize-winning scientist who studies telomeres has compared them to
aglets - the plastic or metal sheath covering ends of shoelaces. When
aglets wear down, the shoelace is exposed to fraying and degradation
from environmental forces.Eisenberg turned to the Cebu
Longitudinal Health and Nutrition Survey, which has tracked the health
of over 3,000 infants born in 1983-1984 in Cebu City in the Philippines.
Researchers collected detailed data every two months from mothers on
the health and feeding habits of their babies up through age two.
Mothers reported how often their babies had diarrhea - a sign of
infection - as well as how often they breastfed their babies.
As these babies grew up, scientists collected additional health data
during follow-up surveys over the next 20 years. In 2005, 1,776 of
these offspring donated a blood sample. By then, they were 21- or
22-year-old young adults.
Eisenberg measured telomere length in cells from those blood
samples. He then combined the data on adult telomere length with
information about their health and feeding habits as babies.
He found that babies with higher reported cases of diarrhea at six to
12 months also had the shortest telomeres as adults. This six-month
period is the typical age for weaning infants, as well as a time of
increasing mobility and exploration. It is also a time when infectious
diseases in infants reach their peak. Based on the environment and
public health situation in Cebu City at the time, these cases of
diarrhea were most likely brought about by infection, Eisenberg said.
Diarrheal infection is a very serious global health concern as it is
the second leading cause of death in children under age five. The
association Eisenberg found between this infection and telomeres is
large enough that it might influence aging in important ways. For
example, those with an average level of diarrheal infection as babies,
compared to those who with no reported infections, showed the equivalent
of three additional years of telomere "aging" - based on the rate of
telomere shortening among middle-aged adults.
One explanation is that the adults have shorter telomeres because
they had more infections as infants. Infections spur increased cell
replications and inflammation, both of which can shorten telomeres. But,
Eisenberg said, another explanation is also possible.
"It could also be that they had shorter telomeres at birth," said
Eisenberg. "And perhaps as a result, they were more susceptible to
infections at six to 12 months and maintained these short telomeres into
adulthood." If this were the case, then telomeres may be an important
determinant of whether or not children around the world succumb to
Surprisingly, he found no association between breastfeeding by mothers and telomere length in their offspring as adults.
"We were expecting to see a relationship between breastfeeding and
telomere length because babies receive maternally-produced antibodies
through breastmilk, which can help them fight off pathogens while their
own immune systems are developing," said Eisenberg. "In addition,
breastfed babies are less likely to be exposed to infectious agents
through contaminated food and water."
In addition, one study from 2016 reported that, among 121 Latino
children in California, exclusive breastfeeding in the first six weeks
after birth was associated with longer telomeres at age four or five. But
there are many reasons that could explain the difference between the
2016 study in California and this new study from the Philippines,
"If breastfeeding does effect telomere length, it could be that the
effect goes away by age 21," said Eisenberg. "Also, infants in these
studies were from vastly different parts of the world - which likely
affects the pathogens they were exposed to and the other typical
parenting habits of women who breastfeed."
Only more data on health, telomere length and environment can resolve the debate, Eisenberg concluded.