We investigated for the first time the sensitivity of all five adiposity indices,
including BMI, in assessing risk for DMT2, CHD, hypertension, dyslipidemia and metabolic
syndrome in an adult Arab population on two separate large-scale cohorts. First we
observed that VAI was most predictive of DMT2 and MetS as compared to the other indices,
including BMI, in cohorts 2008–2009 and 2013–2014, respectively. Several studies on
VAI confirm its significant association to glycemia-related biomarkers, including
adipocytokines 13], 14] and has recently been proven to be a reliable indicator of overt metabolic syndrome
21]. While this finding is strongly in favor of VAI’s increasing clinical use, it is
interesting to note that the concept of VAI for use in non-Caucasian populations needs
to be further tested. VAI is a gender-specific model derived from BMI, waist circumference,
triglycerides and HDL-cholesterol from healthy normal/overweight adult Caucasian populations
22], hence, its use in other ethnic groups, such as the ones used in this study should
be interpreted with caution. The sensitivity of VAI to CHD was not far from WHR, especially
in the 2013–2014 cohort and this was somehow expected, as several cases in the CHD
group harbor DMT2. It has been reported that CHD is more severe in patients with DMT2
and VAI is strongly associated with the severity of CHD 23].
With regards to the best adiposity index for determining CHD, WHR was superior among
other indices, confirming the recent report of Mousavi in a Middle-Eastern population
that WHR change was associated with incident mortality, something not observed with
BMI and waist circumference 24]. Our findings are also in accordance with several studies done using different populations,
asserting that WHR is superior to other indices, such as BMI, in predicting mortality
and cardiovascular events 25]–27]. Furthermore, it is somehow expected that WHR and waist circumference, markers of
abdominal obesity, together with other indices that utilized waist circumference as
part of the mathematical model (WHtR and VAI) to be better in predicting harder outcomes
related to vascular health than BMI and BAI 28], with waist circumference alone being sensitive in determining dyslipidemia and MetS.
As mentioned previously, several populations have assessed the clinical significance
of the various anthropometric indices and attempted to determine which ones are best
for use in the general population. In Singapore, where the general population was
less heterogenous than that of our study, they found that BAI was not better than
BMI or WHtR in identifying persons at risk for CVD 29]. This is in line with our present findings, where BAI was the least sensitive in
determining the cardiometabolic diseases studied. Furthermore, we found that WHtR
was most sensitive, albeit quite modest, in determining hypertension in the Arab population,
at least in the 2008–2009 cohort. This finding also supports the notion that probably,
at least in the Arab population, WHtR can also be used as a predictor for hypertension,
as several large-scale studies done in different ethnic groups also attest its superiority
over BMI (and waist circumference) for detecting cardiometabolic risk factors 30]–32].
It is important to highlight that the sensitivity of the various adiposity indices
were determined and compared from two independent cohorts, with differences not only
in time period but also in the subject selection. With the exception of WHR, which
maintained supremacy over other indices in predicting CHD, overall, there was no “bestâ€
index, as the sensitivity levels of the adiposity indices were modestly near one another.
Furthermore, VAI as a visceral fat function indicator is the only index used which
contains blood parameters that directly affect variance in insulin resistance 33], hence, the bias in comparison to anthropometric indices. What the present study
clearly suggests is that measures of abdominal adiposity maybe more clinically relevant
than BMI and BAI in their ability to detect cardiometabolic diseases in the Arab ethnic
population. Abdominal fat accumulation has been consistently linked to cardiovascular
prognosis and vascular complications 34], 35]. In particular, visceral adiposity influences vascular health in its association
with incident hypertension and its close associations to the cardiometabolic complications
of obesity 36], 37], making it a promising target of therapy for cardiometabolic diseases 38].
The authors acknowledge several caveats. The downsizing of the 30 original groups
to 5 may have created bias in the sensitivity of adiposity indices. While it may have
been ideal to assess the different diseases as a single entity without any comorbidity,
the intention was to maximize the sample size since the other groups were smaller
and combining them into a bigger group based on the presence of a single hard outcome
(CHD, DM, etc.) may hold more strength than simply excluding the group from the analysis.
Also, the findings did not include other relevant factors such as physical activity
and diet, as well as other biomarkers of adiposity and diagnostic markers (HbA1c and
imaging tests) in the assessment of adiposity indices. Nevertheless, the findings
are robust and support other several large-scale studies that highlight the clinical
significance of the various anthropometric parameters commonly used in epidemiologic
studies. It is also the first of its kind in the Arab population, where the incidence
of cardiometabolic diseases are more common than in other groups, reinforcing ethnic-specific
differences in the manifestation of insulin resistance-related diseases 39].
In summary, we determined for the first time the sensitivity of 6 anthropometric indices
(BMI, waist, WHR, WHtR, BAI and VAI) in determining cardiometabolic diseases in the
adult Arab population. In at least one cohort, VAI is most sensitive in determining
DMT2 and MetS (together with waist circumference), WHR in CHD, WHtR in hypertension
and waist circumference in dyslipidemia, highlighting the importance of body fat distribution,
abdominal obesity in particular, in assessing overall cardiometabolic risk. These
screening tools should be promoted for clinical use and their predictive values noted
in assessing at risk Arab adults.