 “Life
is a disease; and the only difference between one man
and another is the stage of the disease at which he lives.
You are always at the crisis: I am always in the convalescent
stage,” wrote George Bernard Shaw in his 1921 play
Back to Methuselah.
The
969-year-old Methuselah — the biblical character
synonymous with longevity — would have had a pretty
easy go of convalescence especially following surgery
according to new research that shows that the rate of
surgical site infections (SSIs) drops once patients
pass the 65-year mark.
Dr Keith Kaye of Duke University
and colleagues report that SSIs increase about 1% per
year from age 17 to 65 and then decrease by about 1%
per year after age 65. In their study, published in
the April 1 issue of the Journal of Infectious Diseases,
they noticed that when age was studied as a dichotomous
variable, being over 65 was associated with an increased
risk of SSI; but when age was analyzed as a continuous
variable, the risk of SSI decreased after age 65. In
their study, there were no surgical site infections
in patients over 95 years.
The researchers studied 144,485 patients
admitted to 11 southeastern US hospitals between February
1991 and July 2002 for various types of surgical procedures.
Overall, 1,684 or 1.2% developed surgical site infections.
AGE
OLD SECRETS
A host of earlier studies have come up with contradictory
results — some indicating that SSI risk increased
in old age while others were more in line with these
recent findings. All this past research has led many
in the medical field to believe that an increase in
age and SSIs are directly related — but no one
is exactly sure how.
The authors of the current study
stand firmly behind their findings and even go as far
as to offer explanations to back them up. One suggestion
is that those over 65 who aren’t contraindicated
for surgery might be less sick. “In addition,
the decreased risk for the very old patients (ie, over
age 80) may be due to a ‘hardy survivor’
effect,” suggest the authors in their study. “In
other words,” they add, “persons who survive
to much older ages may have a genetic makeup that enables
them to better withstand threats to health than some
middle-aged persons.”
Another possibility put forward might
be that SSIs “were detected less frequently in
older patients than in younger patients because the
clinical manifestations of infection, such as fever,
were atypical or were not present.” Some skeptics
may suggest that perhaps older patients have operative
procedures with low risk of SSI while younger ones underwent
more complicated surgeries with greater risks. However,
the authors counter that “the distribution of
types of operative procedures was similar for patients
under age 65 years of age and for patients over 65 years
of age.”
MORE
INVESTIGATION NEEDED
In an editorial accompanying the study, Drs Thomas
Talbot and William Schaffner of Vanderbilt University
called Dr Kaye’s study “impressive,”
though note it relied heavily on data from community
instead of university hospitals. “Patients may
be less severely ill than those in a university hospital
and thus may have a lower risk of surgical site infections,”
they remark. “Despite these limitations, the study
by Kaye et al has many strengths. Primarily,
the sheer volume of patients and procedures studied
affords substantial power to their findings,”
they add.
All agree
that future investigations are needed to answer several
questions, particularly “If increasing age is
truly associated with decreased SSIs, is there a biologically
plausible physiologic explanation for such findings?”
J Infect Dis Apr
2005;191:1056-62
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