Editor—Ebrahim et al studied whether blood cholesterol concentrations are predictive for haemorrhagic and ischaemic stroke in a large cohort of young and middle aged Korean civil servants.1 They found that low concentrations of cholesterol were associated with haemorrhagic stroke while high concentrations were associated with ischaemic stroke.
The incidence of stroke rises sharply with increasing age. The overwhelming majority of all strokes occur in subjects aged 70 and over. The mean age of the participants in this study was about 42 (SD 9). This means that 95% of study participants were under 60 at baseline and therefore under 70 at end of follow-up. This is important since the predictive value of total cholesterol concentration for cardiovascular mortality is heavily dependent on age. After 70 there seems to be no association with cardiovascular mortality,2 while after 80 high total cholesterol concentration might even be beneficial.3,4 A similar pattern with age probably also holds for cholesterol and risk of stroke.5
Figure 1.
Credit: GEOFF KIDD/SPL
We agree with the authors that the burden of stroke is becoming greater as the population ages, making its prevention a priority. However, in this case it is not possible to simply transpose the findings from young and middle aged people to the elderly population at risk. Therefore, the study by Ebrahim et al does not contribute significant knowledge whether total cholesterol concentration is a risk factor for the vast majority of strokes.
Competing interests: None declared.
References
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