Death and
serious complications more likely in patients with vitamin D deficiency, study
suggests
Patients with low blood levels of vitamin D are at increased risk of death and
serious complications after noncardiac surgery, suggests a study in Anesthesia
& Analgesia.
"Vitamin D
concentrations were associated with a composite of in-hospital death, serious
infections, and serious cardiovascular events," according to the new
research by Dr Alparslan Turan and colleagues of the Cleveland Clinic. They
believe their results warrant further study to see if giving vitamin D
supplementation before surgery can reduce the risk of these adverse outcomes.
Lower Vitamin D Levels
Linked to Higher Surgical Risk
The researchers analyzed
the relationship between vitamin D level and surgical outcomes in approximately
3,500 patients who underwent operations other than heart surgery between 2005
and 2011. Only patients who had available data on vitamin D levels around the
time of surgery—from three months before to one month afterward—were included
in the study.
The concentration of
vitamin D (specifically, 25-hydroxyvitamin D) in blood samples was analyzed as
a risk factor for death, cardiovascular events, or serious infections while in
the hospital. The analysis included adjustment for other factors such as
demographic characteristics, medical conditions, and type and duration of surgery.
Most patients did not
meet the recommended 25-hydroxyvitamin D concentration of greater than 30
nanograms per milliliter (ng/mL). The median vitamin D level was 23.5
ng/mL—more than 60 percent of patients were in the range of vitamin D
insufficiency (10 to 30 ng/mL). Nearly 20 percent had vitamin D deficiency
(less than 10 ng/mL).
"Higher vitamin D
concentrations were associated with decreased odds of in-hospital
mortality/morbidity," the researchers write. For each 5 ng/mL increase in
25-hydroxyvitamin D level, the combined risk of death, cardiovascular events,
or serious infections decreased by seven percent.
Patients at the lowest
level of 25-hydroxyvitamin D (less than 13 ng/mL) were at highest risk of death
or serious complications. Those with higher vitamin D levels (up to 44 ng/mL)
had about half the risk as those in the lowest group. The association with low
vitamin D was statistically significant only for cardiovascular complications,
although there were "strong trends" for mortality and infections.
Further Study Needed to
Determine Cause and Effect
"Vitamin D
deficiency is a global health problem," according to Dr Turan and
coauthors. In addition to protective cardiovascular and neurological effects,
vitamin D plays an important role in the immune system.
The high rates of vitamin
D insufficiency and deficiency in the surgical patients studied are consistent
with previous findings in the general population. In recent years, studies have
suggested that vitamin D levels may affect a wide range of health outcomes.
Patients undergoing
surgery are at risk of cardiovascular and infectious complications, both of
which may be aggravated by vitamin D deficiency. Previous studies found no
increased risk of adverse outcomes related to vitamin D levels in patients
undergoing cardiac surgery. It may be that the tissue injury and inflammation
associated with heart surgery overwhelms any potential protective effect of
vitamin D.
However, Dr Turan and
colleagues note that their study had some important limitations of their
study—especially the fact that it included only patients who had recent
measurements of vitamin D levels. They may represent a less-healthy group,
introducing a potential source of selection bias.
The study can't determine whether
there is any cause-and-effect relationship between vitamin D levels and the
risk of adverse outcomes. Dr Turan and colleagues suggest a formal randomized
trial to evaluate whether preoperative vitamin D supplementation can reduce the
risk of serious complications and death after surgery.
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