Clinical Question:
Does a higher fasting glucose level or a higher 2-hour postprandial glucose
level in men predict mortality?
Bottom Line:
These data support the decision to lower the FPG diagnostic for diabetes
from 7.8 to 7.0 mmol/l, show that both IFG and impaired glucose tolerance
have risks between the normal and diabetic ranges, and show that the OGTT
adds predictive power to that of FPG alone and should not be abandoned. The
lowering of IFG to 5.6 mmol/l from 6.1 mmol/l, at least for mortality, is,
however, not supported by our results.
Reference:
Sorkin JD, Fleg JL, Muller DC, Andres R. The relation of fasting and 2-h
postchallenge plasma glucose concentrations to mortality. Diabetes Care
2005;28:2626-32.
Study Design:
Cohort (prospective)
Synopsis:
Under the auspices of the National Institutes of Health, American Diabetes
Association, and World Health Organization, expert committees lowered the
fasting plasma glucose (FPG) concentration diagnostic for diabetes from 7.8
to 7.0 mmol/l and defined 6.1-6.9 mmol/l as impaired fasting glucose (IFG)
and <6.1 mmol/l as normal fasting glucose. In 2003, IFG was lowered to
5.6-6.9 mmol/l and normal fasting glucose to <5.6 mmol/l. Reports of the
relationship between glucose concentration and all-cause mortality have been
inconsistent. It is not known if the 2-h plasma glucose (2hPG) concentration
from an oral glucose tolerance test (OGTT) adds to the predictive power of
FPG. We followed 1,236 men for an average of 13.4 years to determine the
relationship between both FPG and 2hPG and all-cause mortality. Risk for
mortality did not increase until the FPG exceeded 6.1 mmol/l. Risk increased
by approximately 40% in the 6.1-6.9 mmol/l range and doubled when FPG ranged
from 7.0 to 7.7 mmol/l. A combination of the 2hPG and FPG allowed better
estimation of risk than the FPG alone. Within any category of FPG, risk
generally increased as the 2hPG increased, and within any category of 2hPG,
risk generally increased as the FPG increased.
One important caveat: This type of study shows a relationship, which may or
not be a cause. In other words, even though higher glucose levels were
associated with higher mortality, it doesn't necessarily mean that lowering
blood glucose levels will reverse this risk; the increased glucose levels
could simply be a marker and not a cause of mortality. |