Fig. 1
West–east gradient in CVD mortality
Fig. 2
Expenditure on health care
Within Europe, CVD mortality has in general declined in the West and increased in the East, although it is starting to decline in some Eastern European countries [3]. Brazil has seen a steady reduction in total CVD standardized mortality rates of from 287 to 162/100,000 over the 24-year period from 1980 to 2003 [4].
Atherosclerosis: Slow Development, Fast Death
Atherosclerosis has its antecedents in utero, and may be evident as fatty streaks in childhood (Fig. 3). It generally develops insidiously over many years before becoming clinically manifest in middle age or later. Obstructive disease may present as angina, whereas a potentially fatal acute coronary syndrome represents plaque rupture.
Fig. 3
The development of atherosclerosis
Within about two hours of a coronary artery occlusion due to plaque rupture, one half of deaths will have occurred and survivors, if not in time for percutaneous intervention (PCI) or thrombolysis, are likely to have sustained irreversible myocardial damage [5]. The implications of these observations are that treatments such as PCI, while impressive for those fortunate enough to be in time to benefit from them, will of course be inapplicable for those who suffer sudden or early death, and palliative for many others due to the advanced nature of the underlying disease and the likelihood of irreversible myocardial damage.
Risk and Causation
A risk factor may be defined as a characteristic that is associated with the subsequent development of a disease. Establishing a causal relationship between a factor associated with a disease is generally straightforward if there is a single cause, for example hypothyroidism. It is more complex if there is a single cause but other factors determine if it becomes manifest, such as tuberculosis. It is more complex again if there are multiple factors, which could be causal, many of which are co-incidental characteristics of a rising standard of living.
Originating in the work of Doll and Hill [6] relating to smoking and lung cancer, a list of criteria has been developed to allow a judgment as to whether an association between a putative factor and CVD is sufficiently likely to be one of cause and effect to justify public health action:
1.
Is causality biologically plausible?
2.
Is the relationship strong?
3.
Is it graded (the stronger the exposure, the greater the likelihood of disease)?
4.
Temporality—is it clear that the presence of the factor preceded the development of the disease?
5.
Is it independent in that its effect is still evident after adjusting for the effects of other factor?
6.
Is the association consistent in repeated studies?
7.
Is there agreement between different scientific disciplines (basic science, pathology, epidemiology et cetera)?
8.
Does reducing or removing the factor reduce the risk?
Based on a century of grinding research, the following conclusions may be reasonable with regards to risk factors and CVD:
Clearly causal: High saturated fat die, blood cholesterol level, tobacco smoking, hypertension.
Probably or indirectly causal: Overweight, physical inactivity, Lp(a), diabetes, renal failure, triglycerides, social deprivation.
Uncertain: HDL cholesterol, fibrinogen, high sensitivity CRP, homocysteine.
In the search for direct causes of CVD, the critical importance of the “causes of the causes” should not be underestimated, in particular social deprivation, which drives many of the direct causes of CVD and other causes of premature death; the poor really do die young [7].
Arising, Table 1 is a conventional classification of risk factors.
Table 1
Lifestyles and characteristics associated with increased risk of future CVD
Lifestyles | Biochemical or physiological characteristics (modifiable) | Personal characteristics (non-modifiable) |
|---|---|---|
Diet high in saturated fat, cholesterol and calories | Elevated plasma cholesterol (LDL cholesterol) Low plasma HDL cholesterol | Age Sex |
Tobacco smoking | Elevated plasma triglycerides < div class='tao-gold-member'>
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