Canadian researchers are reporting
what they say is a better way to identify
teens whose cholesterol levels put them at
high risk for heart disease as adults.
The current guidelines, established in 1992
in the United States, have limited ability
to single out younger people who will be at
high risk in the future, said the research
team led by Ian Janssen, a professor of kinesiology
and epidemiology at Queen's University in
Kingston, Ontario.
"The essential difference with our method
is that it takes into account the age and
gender of a teen when determining who is at
risk," Janssen said.
The report was expected to be published in
the Aug. 29 issue of Circulation.
Janssen and his colleagues used data from
the U.S. National Health and Nutritional Examination
Surveys conducted between 1988 and 2002. Information
on more than 6,000 participants aged 12 to
20 was used to develop age- and gender-specific
growth curves for total cholesterol, LDL ("bad")
cholesterol, HDL ("good") cholesterol
and triglyceride fat levels. These curves
are similar to the curves used to monitor
and estimate height and weight patterns in
children and teens.
The cholesterol curves were then linked to
adult cholesterol and fat levels that predict
cardiovascular risk. The result is a reading
that can predict a teen's future risk of heart
disease, Janssen said.
The major advantage of the new guidelines
is that they take into account the fluctuations
in cholesterol and fat levels that occur with
age, Janssen said. "We know that your
cholesterol levels change significantly from
age 2 to 20, changes that go with maturation,"
he said.
The current guidelines published by the U.S.
National Cholesterol Education Program don't
take those age-related changes into account,
Janssen said. They simply say that any teen
in the top 5 percent of readings is at risk,
an entirely arbitrary level, he said.
"Why not choose the 90th percentile
instead of the 95th?" he asked. "There
is no real risk attached to either of these
percentiles."
Gender must also be taken into account because
the curves for the two sexes differ, the Canadian
researchers said. For example, male levels
of LDL cholesterol decrease early in the teen
years, then start rising at about 15 years
of age, while female levels increase steadily
from 12 to 20.
The current federal guidelines, endorsed
by the American Heart
Association, recommend cholesterol
screening tests for adolescents whose parents
have abnormal cholesterol levels or if there
is a family history of cardiovascular disease
before age 50.
"Hopefully, physicians already are testing
those teenagers," Janssen said. "Hopefully,
this method provides a better way to identify
those at high risk."
