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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 4, July/August 2016
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AFRICA
They also impair the erythrocyte membrane and maturation
of red blood cells. As a result, they lead to the release of
juvenile erythrocytes from bone marrow into the circulation.
21
Additionally oxidative stress can affect the production of red
blood cells. These cells have tremendous antioxidant capacity and
are a primary oxidative sink, nevertheless, they are susceptible to
oxidative damage.
The oxidative stress associated with many clinical conditions
brings about raised RDW.
8
Activation of neurohumoral
mediators (such as angiotensin II and the sympathetic system
hormones) as well as inflammation and oxidative stress stimulate
abnormal erythropoiesis. Therefore the survival of red blood
cells is diminished on account of ineffective erythropoiesis.
7,21
All of these conditions can be observed in atherosclerotic
cardiovascular disease, leading to elevation of RDW.
In the present study, we aimed to investigate whether RDW
had an association with AS, which is an indicator of subclinical
atherosclerosis. We hoped to recognise atherosclerosis at an early
stage using RDW level, which is a routine parameter of a full
blood analysis in most patients. Because RDW could be affected
by many clinical conditions, we included healthy volunteers with
a high BMI in the study. Those with low haematocrit levels or
who had undergone blood transfusions in the previous six month
were excluded. We did not investigate whether there were iron,
folic acid or cyanocobalamine deficiencies in the subjects, since
the mean haematocrit level of the study population was normal.
The results of this study support our hypothesis, and indicate
the strong positive correlation between log-RDW and aortic
PWV. Also, age, resting heart rate and BMI were positively
correlated with aortic PWV. However, multiple regression
analysis suggested that log-RDW, resting heart rate and age were
independent predictors for aortic PWV.
It is known that elasticity of the arteries is impaired with
advanced age.
22,23
Similarly, it has been reported that increased
resting heart rate is associated with aortic stiffness and
atherosclerosis.
24,25
Our study supports these results. However,
an interesting result of our study was that RDW was the most
important independent predictor for aortic PWV in the stepwise
regression analyses.
In clinical practice, we believe that RDW and resting heart
rate, especially with advanced age, can indicate AS or subclinical
atherosclerosis in obese and overweight individuals. Therefore,
these patients may be identified at an early stage of atherosclerosis
and medically treated earlier and more aggressively, before the
development of any symptoms of atherosclerotic disease.
Aortic PWV, which is the travelling time of the pulse
wave from one point to another, indicates arterial stiffness,
and high values reflect atherosclerotic cardiovascular disease
with or without symptoms.
4,6,26
Atherosclerotic disease may be
determined by various symptoms or acute events; however,
subclinical atherosclerosis is not be easily recognised. Therefore,
some determinants of AS, such as aortic PWV and Aix75, have
been used to detect subclinical atherosclerosis.
Aortic PWV is the gold standard to evaluate AS and
cardiovascular risk, as has been shown in many studies.
13,16,25,26
A number of recently published studies have demonstrated
elevated aortic PWV in several cardiovascular disorders. Kullo
et al
. showed that aortic PWV was related to subclinical
coronary atherosclerosis, detected by the presence of coronary
artery calcium using computed tomography.
4
Another study by
Catalano
et al
. pointed out that augmentation index in patients
with peripheral artery disease, which is another parameter of
AS, was higher than in the normal population.
27
Our study
showed no changes in aortic Aix75 between the case subjects and
controls, unlike aortic PWV.
Obesity is an important risk factor for various health problems,
including atherosclerosis. It has recently been demonstrated
that people using high-fat dairy products had a higher aortic
PWV and carotid media thickness compared with those using
low-fat dairy products.
28
Vayá
et al.
and Fujita
et al.
reported an
elevated RDW in obese subjects, and our results are compatible
with these.
29,30
However, previous studies asserted that different
causes might be responsible for this elevation. Among them,
inflammation and hyposideraemia were blamed as responsible
mechanisms.
29,30
There is no consensus on the pathogenesis of the
rise in RDW in obese and overweight populations.
We also demonstrated a raised RDW and PWV in obese
and overweight persons compared with the healthy controls.
However, when the case group was divided into two subgroups
according to aortic PWV, the RDW of the overweight and obese
subjects with low aortic PWV was similar to that of the controls.
Conversely, those with high aortic PWV had a considerably
elevated RDW compared with the controls and the other group
(obese and overweight with low PWV).
Also, although there was a linear correlation between BMI
and RDW as well as aortic PWV, stepwise regression analyses
showed that log-RDW was an independent predictor in the final
models for the estimation of aortic PWV. These results indicated
that impaired aortic elastic properties with high aortic PWV may
contribute to increased RDW in overweight and obese patients,
apart from the previously stated reasons.
There are some limitations of our study. The main limitation
is the relatively small sample size. Another is that iron, folic
acid and cyanocobalamin levels were not determined in the
participants. However, volunteers with a haematocrit lower than
35% were not included in the study. Lastly, we did not evaluate
adipocytokines, such as leptin, adiponectin, resistin, chemerin
and visfatin, knowing their relationship with atherosclerosis and
angiogenesis.
Conclusion
This study indicated that raised aortic stiffness may be responsible
for elevated RDW values in obese and overweight persons.
Therefore, RDW may help to provide an early recognition of
atherosclerosis using a simple test instead of more sophisticated
devices, particularly if evaluated together with resting heart rate
in the older population.
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