Elevated total cholesterol: its prevalence and population attributable fraction for mortality from coronary heart disease and ischaemic stroke in the Asia-Pacific region

Woodward et al.
Eur Jrnl of Cardiovascular Prevention & Rehabilitation

Special Introduction by the Authors
Raised serum total cholesterol is, together with age, sex, smoking and raised blood pressure, one of the major risk factors for coronary heart disease and ischaemic stroke. Many studies have shown that the association between cholesterol and each of these diseases (the leading causes of death in many countries) is continuous (linear, on a logarithmic scale) down to low levels of cholesterol below conventional thresholds of ‘cardiovascular safety', such as 6.2 mmol/l (240 mg/dl). Based on observations across the world, the World Health Organisation's Global Burden of Disease project has identified the theoretical minimum cholesterol distribution as that with mean 3.8 mmol/l and standard deviation 0.6 mmol/l.

The Asia-Pacific region has the largest population of any region of the world, and many countries in this region have recently experienced, or will soon experience, a transition to Western diets and lifestyles. This may be assumed to be associated with increases in blood cholesterol, and thus ischaemic diseases. A paper by Mark Woodward and colleagues, in the August issue of the European Journal of Cardiovascular Prevention and Rehabilitation, includes the results of a systematic review of nationally representative surveys of cholesterol levels across the region. Most studies reported the prevalence of cholesterol that was 6.2 mmol/l or greater - this ranged from 4% in the Philippines to 27% in Australia (for both sexes). Using data from the Asia Pacific Cohort Studies Collaboration, it was estimated that the percentage of deaths due to coronary disease that was attributable to cholesterol of 6.2 mmol/l or more, for men in the region, ranged between 1% in Malaysia to 12% for Australia. For women, the corresponding percentages were 2% and 10%. Similar, but about 1% higher, estimates were found for ischaemic stroke. However, these estimates, whilst appropriate to some guidelines (such as the US ATPIII definition of high cholesterol) underestimate the true effect of cholesterol by ignoring both the theoretical minimum distribution and the measurement error in recording cholesterol on only one occasion (regression dilution bias). Taking these issues into account, Woodward et al show that the percentage of heart disease and ischaemic stroke deaths due to non-optimal cholesterol are about twice as large as those for ATPIII high cholesterol. Whilst for the less developed countries of the Asia-Pacific region, virtually no deaths may be due to non-optimal cholesterol (because cholesterol is optimally distributed in these countries), most Asian and Pacific countries show between 20 and 40% of coronary deaths being due to non-optimal cholesterol, in both sexes. For ischaemic stroke, the percentages typically range between 10-20% for men and 15-30% in women. In Australia and New Zealand, which have cholesterol distributions akin to much of Europe, about 46% of coronary and 27% of ischaemic stroke deaths amongst men were estimated to be due to non-optimal cholesterol. Amongst female Australasians, the corresponding percentages are 41 and 35%.

These findings suggest that number of deaths from ischaemic disease that are attributable to elevated cholesterol are greater than previously estimated. Public health interventions in the populous Asia-Pacific region, for example to reduce consumption of dietary fats, would be expected to have a tremendous effect on reducing cholesterol levels and thus reducing the immense number of ischemic heart and stroke deaths that may otherwise be anticipated in the region in years to come.

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