Low levels of vitamin D are associated with an important
early-warning sign of cardiovascular disease in patients with HIV, US
investigators report in the April 1st edition of Clinical Infectious Diseases.
The research showed a significant relationship between
vitamin D insufficiency and thickening of the carotid artery.
“To our knowledge, this study is the first to report the
association between vitamin D status and atherosclerotic vascular disease,
measured by cIMT [carotid intima-media thickness], in HIV-infected persons,”
comment the authors.
A number of studies have already shown that large numbers of
HIV-positive patients have low levels of vitamin D. In the general population,
vitamin D insufficiency has been associated with cardiovascular disease.
Investigators from the University of California-San
Francisco Study of the Consequences of the Protease Inhibitor Era cohort
therefore sought to establish the prevalence and risk factors for low vitamin D
levels in patients with HIV, and the relationship between vitamin D deficiency
and sub-clinical atherosclerosis (hardening of the arteries), measured by cIMT.
Their cross-sectional, or “snap-shot” study involved 139
patients, whose average age was 45.
The majority (84%) were male, 54% were white and 32% were black.
Three-quarters of patients were taking antiretroviral therapy and 71% of these
individuals had a viral load below 1000 copies/ml. The median CD4 cell count
was 336 cells/mm3.
Between a fifth and a third of patients had traditional risk
factors for cardiovascular disease such as smoking, high blood pressure, or
Over half (52%) of patients had vitamin D deficiency (below
30 ng/ml). Factors associated with insufficient levels of the vitamin included black
race (relative risk [RR] = 2.62; 95% CI, 1.80-3.82) and a higher body mass
index, or BMI (RR = 1.25 per BMI increase of 5; 95% CI, 1.03-1.51). Both of
these risk factors have been observed in other research.
Taking vitamin D supplements reduced the risk of
insufficiency by almost a third (RR = 0.70; 95% CI, 0.52-0.95).
During the first six months of HIV therapy, patients treated
with a non-nucleoside reverse transcriptase inhibitor (NNRTI) were 2.5 times
more likely than patients taking a protease inhibitor to have low levels of
vitamin D. The investigators call for this finding “to be re-evaluated in other
cohorts with longer NNRTI exposure.”
Further analysis showed that patients with vitamin D
deficiency were more likely to have increased cIMT.
The relationship between vitamin D insufficiency and
increased cIMT remained significant (p = 0.021) even after adjustment for
traditional risk factors for hardening of the arteries, HIV-related factors
such as viral load and duration of antiretroviral therapy, and lipid levels.
“We found that HIV-infected persons with vitamin D
insufficiency had a mean cIMT that was 0.13 mm greater than the mean cIMT for
those with normal vitamin D levels, even after extensive risk adjustment,”
comment the authors.
They note that increased cIMT is “a strong predictor of
future clinical events.” In the general population, an increase of 0.13 mm in
cIMT is associated with an 18% increase in the relative risk of stroke and 15%
increase in the relative risk of heart attack.
“We found that vitamin D insufficiency was common, and it
was significantly associated with cIMT independent of traditional and
HIV-related risk factors,” write the authors.
But they emphasise that “vitamin D insufficiency is a
readily modifiable risk factor” which can be diagnosed using simple blood tests
and treated with high-dose supplements.
The authors conclude that their findings “provide the basis
for future studies that prospectively examine the risk of clinical
cardiovascular disease associated with vitamin D status over time and the
effects of high-dose vitamin D supplementation on cIMT.”