Is the calculation of a risk factor without reference to a pathophysiology of any real benefit ?
Even though the QDScore is the first algorithmn to calculate the 10
year risk for type 2 diabetes, how will individuals or GPs respond to a
positive result ? Does the knowledge lead to an effective treatment ? If
so, how does the treatment relate to a pathophysiology ?
A major problem is that the authors failed to recognise that there
was a common feature in most of the risk factors. Thus,aging, high
BMI,smoking status, hypertension and cardiovascular disorders are all
associated with an increase in blood viscosity and a reduction in red cell
Furthermore, the selected age range (25 to 79 years) appears to have
been treated as a continuum, but during the aging process, from about 50
years of age, blood viscosity rises and red cell deformability is reduced
in concert with an increase in fibrinogen levels. And the selected range
excludes children and adolescents who have been diagnosed with type 2
diabetes. In childhood obesity, a high BMI has been shown to be
associated with similar changes of fibrinogen levels, blood viscosity and
red cell deformability as occurs in the aging process. (1) Others have
published similar findings. Ernst et al (2) have reported that in grossly
obese individuals on a low calorie diet, blood viscosity was reduced and
red cell deformability was increased.
The effects of smoking were assessed as smokers or non-smokers, but
the increase in blood viscosity is related directly to the numbers of
cigarettes smoked. So the risk from smoking 4 cigarettes daily is greatly
different from that of smoking 40 cigarettes daily. Cessation of smoking
reverses the smoking-related changes.
In 1930 attention was drawn to the fact that blood pressure was
related directly to blood viscosity and subsequent studies have confirmed
that relationship, although it has failed to gain clinical recognition.
There is a large literature which documents the association of increased
blood viscosity with cardiovascular disorders. Although it was recognised
that social deprivation was associated with other risk factors (diet,
obesity, smoking) it was not recognised that the effects of all three
factors would be cumulative, which would explain the poor outcome. It is
of some relevance that there are published reports which show that type 2
diabetes is associated with increased blood viscosity and poorly
deformable red cells. Those changes may be exacerbated by similar changes
in risk factors.
Therefore of the 9 risk factor used in the development of the
QDScore, 7 factors share the common feature of altered blood rheology.
How does this impinge on the QDScore ? What benefits will flow from
calculating a QDScore, in comparison with simply recognising that altered
blood rheology is the major factor even in the pre-diabetic state ? An
important fact is the blood rheology changes are potentially treatable.
Huang et al (3) reported that Gingko biloba extract (Egb 761) lowered
blood viscosity and improved red cell deformability and, "...it
effectively improved retinal capillary flow rate in type 2 diabetic
patients with retinopathy." Because of the beneficial effects of the
omega-3 fatty acids in fish oil in other disorders, it is surprising that
this has not been shown in type 2 diabetes. A 1994 report (4) concerning
the consumption of seal oil and salmon by Alaskan Natives, concluded,
"Consumption of seal oil and salmon, high in omega-3 fatty acids, appears
to lower the risk of glucose intolerance and is a potentially modifiable
risk factor for NIDDM in Alaskan Natives."
While it is uncertain to what extent the QDScore would be affected by
recognising that 7 of the 9 risk factors shared a common feature, it does
raise questions about the utility of the algorithm. For that reason, when
faced with pre-diabetic patients, GPs could suggest that they explore the
potential of Gingko biloba extract (Gbl761) at 180mgs daily or fish oil at
6 to 10 grams daily, with the objective of normalising the flow properties
of their blood.
1. Cacciari E, Balsamo A, Palareti G, et al. Haemorheologic and
fibrinolytic evaluation in obese children and adolescents. Eur J Pediatr
1988; 147: 381-4.
2. Ernst E, Weihmayer T, Matrai A, et al. Changes in blood rheology of
grossly obese individuals during a very low calorie diet. In J Obesity
1989; 13 (Suppl 2):167-8.
3. Huang SY, Jeng C, Kao SC, et al. Improved haemorrheological
properties by Gingko biloba extract (Egb761) in type 2 diabetes mellitus
complicated with retinopathy. Clin Nutr 2004; 23: 615-21.
4. Adler AI, Boyco FJ, Schraer CD, et al. Lower prevalence of impaired
glucose tolerance and diabetes associated with daily seal oil or salmon
consumption among Alaska Natives. Diabetes Care; 1994: 1498-501.
Competing interests: No competing interests