|
Even though familial hypercholesterolemia
-- a genetic condition that causes very high cholesterol
levels -- has been linked to the early onset of heart disease,
the risk of early death may vary significantly among
people with the disorder.
Moreover, researchers speculate, the
findings suggest that other factors such as diet and
exercise help determine the overall death risk of people
with the genetic condition.
In a study of an extended family affected
by familial hypercholesterolemia, investigators found that,
over two centuries, about 40% of family members lived
normal life spans.
During the 1800s, members of the family
tended to live longer than average for the time,
but the rate of early death began to rise in 1915, reaching
a peak in the 1950s, according to the authors. Since then,
the life expectancy of the family members has been increasing.
But the investigators found that death
rates varied considerably from branch to branch of the
family tree. During the decades when the family as a whole
had shorter-than-average life spans, some branches of the
family had normal life spans and others had extremely high
rates of premature death.
The wide variations in risk suggest
that environmental factors, such as
-
diet,
-
smoking
-
and physical activity
may interact with genetics to affect
the risk of cardiovascular disease and early death.
It is possible that high levels of "bad"
LDL cholesterol might have protected 19th century family
members from infections common at the time, while the lack
of other heart disease risk factors, such as widespread
cigarette smoking or fatty diets, might have reduced their
risk of death.
Since death rates varied from branch
to branch of the family tree, other genetic factors might
have affected the risk as well. Variations in social class
and in where different branches lived may also have had
an effect.
Whatever the reasons for the variations,
the study shows that even though genes are important in
determining life expectancy, environmental factors also
play a major role.
British
Medical Journal April 28, 2001;322:1019-1023
| 