Carrying a little extra weight
around does not, in itself, increase your patients'
risk of death, according to a landmark study published
in the latest issue of Critical Care. While overweight
people are clearly dying younger than the average, the
excess mortality is concentrated in those who have diabetes.
"It's fair to say that being overweight, even being
somewhat obese, did not bring any extra risk at all
once diabetes was controlled for," says co-author Dr
David Mannino of Kentucky University's Chandler Hospital.
"I think it's time for a reassessment of the link between
obesity and death rates that takes into account the
centrality of diabetes."
The surprising finding is based
on data from over 15,000 participants in the Atherosclerosis
Risk in Communities (ARIC) study. Over a three-year
period, cases of acute organ failure, and of death through
acute organ failure, were analysed using a variety of
risk factors, including obesity, smoking, and diabetes
or blood sugar level.
Needless to say, death rates climbed
with the subjects' weight. But all of the excess mortality
in obese patients appeared closely linked to diabetes
— those without the disease showed no extra risk
at all. "A normal-weight patient with diabetes was much
more at risk than an obese patient without diabetes,"
says Dr Mannino.
The risk for developing acute organ
failure was 2.4% among subjects with diabetes, versus
0.7% in those without the disease. Among those who did
suffer organ failure, both in-hospital mortality (46.5%
versus 12.2%) and three-year mortality (51.2% versus
21.1%) was much higher in subjects with diabetes than
in those without.
DIABETIC
WATCH
Of course, it's clear that obesity remains closely linked
to risk of early death. Participants with a BMI over
30, generally agreed as the cut-off point that defines
obesity, were three times as likely to have diabetes
as those of lower weight (22.4% versus 7.9%). "This
study shouldn't really change the advice given to patients,"
explains Dr Mannino. "Eating well and exercising regularly
can help prevent diabetes as well as obesity. But clinicians
might want to take extra care with normal-weight patients
who are diabetic," he adds.
In fact, the most vulnerable patient
of all could well be the underweight diabetic. This
study could be interpreted as lending support to the
theory that 'nutritional reserves' in heavier patients
may help them fend off acute illness, such as in-hospital
organ failure.
A
GROWING THREAT
Given the glut of research into the health effects of
obesity, it might seem unlikely that no one has ever
tried to tease apart the effects of excess weight and
diabetes until now. "I can't swear there are none,"
says Dr Mannino, "but we did a search and didn't find
any studies that really controlled for diabetes."
These latest findings will lend
support to the growing body of evidence that shows diabetes,
a disease that's striking more and more people at ever-younger
ages, is really the common factor behind millions of
deaths currently attributed to other causes.
According to Health Canada, diabetes
is listed as the seventh leading cause of death in the
country. But it's also one of the fastest growing diseases,
with more than 60,000 new cases of Type II diabetes
diagnosed yearly.
The ARIC study was conducted from
1986 to 1989 and new diabetes treatments have become
available since. But Dr Mannino says his team's findings
are likely valid nevertheless, because as a recent study
in Diabetes Care made clear, the proportion of
patients whose disease is "well controlled" hasn't improved
one iota over the past two decades.
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