BMJ  2005;330:1208 (21 May), doi:10.1136/bmj.330.7501.1208-a

Letter

Secondary prevention of heart disease with statins

Findings are unexpected

EDITOR—Wei et al reported that statins are as effective in the community as in clinical trials in the secondary prevention of coronary heart disease, but they have not commented on some even more surprising results.¹ They reported benefit for calcium blockers, in contradiction of previous findings^2-4 and found blockers to be much more effective than previously thought (odds ratio for risk reduction 0.38 v 0.81 in a previous systematic review²).

We are concerned that these unusually positive findings across the board may reflect an undetected bias in the study design, rather than the true benefit of drug treatment. The marked differences between the intervention and control groups have already been pointed out by Penston [first letter], and most of these differences were controlled for in the analysis. However, the significant rise in statin use from 3% in 1993 to 63% in 2001 means that the intervention and control groups are effectively cohorts from different time periods. This would also affect the results for blockers and calcium blockers, both of which were much more commonly used in the statin group.

It is not possible to draw meaningful conclusions from this study until the effect of date of discharge from hospital is allowed for in the analysis, and we therefore suggest that the authors reanalyse the data to take this into account.

r.fleetcroft{at}uea.ac.uk
University of East Anglia School of Medicine, Health Policy and Practice, Norwich NR4 7TJ

University of East Anglia School of Medicine, Health Policy and Practice, Norwich NR4 7TJ

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Competing interests: None declared.

References

1. Wei L, Ebrahim S, Bartlett C, Davey PD, Sullivan FM, MacDonald TM. Statin use in the secondary prevention of coronary heart disease in primary care: cohort study and comparison of inclusion and outcome with patients in randomised trials. BMJ 2005;330: 821. (9 April.)[Abstract/Free Full Text]
2. Teo KK, Yusuf S, Furberg CD. Effects of prophylactic antiarrhythmic drug therapy in acute myocardial infarction. An overview of results from randomized controlled trials. JAMA 1993;270: 1589-95.[Abstract]
3. Aronow WS. Management of the elderly person after myocardial infarction. J Gerontol A Biol Sci Med Sci 2004;59: 1173-85.[Abstract/Free Full Text]
4. Van der Elst ME, Buurma H, Bouvy ML, de Boer A. Drug therapy for prevention of recurrent myocardial infarction. Ann Pharmacother 2003;37: 1465-77.[Abstract/Free Full Text]

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Relevant Article

Statin use in the secondary prevention of coronary heart disease in primary care: cohort study and comparison of inclusion and outcome with patients in randomised trials

Li Wei, Shah Ebrahim, Christopher Bartlett, Peter D Davey, Frank M Sullivan, and Thomas M MacDonald
BMJ 2005 330: 821. [Abstract] [Full Text] [PDF]