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Duration and extent of cholesterol reduction and risk reduction

 

Clinical bottom line

Reduction in risk of fatal and non-fatal cardiac death depends on both the duration and extent of cholesterol reduction use. The greatest reduction in risk was associated with LDL reduction of at least 1.5 mmol/L for more than two years.


Reference


MR Law et al. Quantifying effect of statins on low density lipoprotein cholesterol, ischaemic heart disease, and stroke: systematic review and meta-analysis. BMJ 2003 326: 1423-1429.


Background

Statins to reduce total cholesterol and low density lipoprotein cholesterol have been available for a decade or more, and are now much used. The evidence here examined reduction of risk against the extent and duration of cholesterol reduction.

Systematic review

Randomised trials of cholesterol reduction by any means were sought, excluding those in which risk factors other than cholesterol were changed, fewer than five ischaemic heart disease events occurred, or in which there was no untreated control group. IHD events were IHD death or non-fatal myocardial infarction (and excluding silent infarcts).

Results

There were 58 trials with 76,000 treated patients and 72,000 controls, with 5,440 and 7,102 respective events, with treatments including fibrates, resins, niacin, statins or dietary change). Results from trials were standardised to a 1 mmol/L reduction in LDL cholesterol by raising the observed odds ratio to the power of 1.0 divided by the observed LDL cholesterol reduction.

Figure 1 shows the effects of duration alone. Full protection depended upon cholesterol reduction for at least two years.

Figure 1: Effect of duration of cholesterol reduction on risk of IHD

Table 1 shows the effects of duration together with the extent of LDL cholesterol reduction. Greater LDL reduction and longer duration of cholesterol reduction yielded larger reductions in risk.

Table 1: Effect of duration and extent of cholesterol reduction on risk of IHD

 

LDL cholesterol reduction (mmol/L)
Years in trials
0.2-0.7
0.8-1.4
≥1.5
1 and 2
6
19
33
3-5
19
31
50
6 or more
21
30
52

Comment

Very useful information, showing that for full benefit, cholesterol reduction has to be large and sustained.