Electronic letters to:

Research:
Igor Karp, Shun-Fu Chen, and Louise Pilote
Sex differences in the effectiveness of statins after myocardial infarction
CMAJ 2007; 176: 333-338 [Abstract] [Full text] [PDF]
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[Read eLetter] Statins after myocardial infarction: the elephant in the room.
Eddie Vos   (12 February 2007)

Statins after myocardial infarction: the elephant in the room. 12 February 2007
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Eddie Vos
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Re: Statins after myocardial infarction: the elephant in the room.

vos{at}health-heart.org Eddie Vos

The study by Karp et al (1) stratifies patients after myocardial infarction by having been prescribed statin, or not. This evidently excludes many patients in the bottom quartile for cholesterol [the approved use of statins in Canada being dyslipidemia] and may induce a 'healthy-user' bias.

Many studies, from Framingham (2) to Vorarlberg (3), show that in the over age 60 group such as in (1), being in the decreasing cholesterol (2) or in the lower quartile for cholesterol groups (3) selects those most likely to die early. Conversely, older patients, selected because of high-cholesterol (and thus more statin use) live longer.

The fact that baseline cholesterol measurements in this drug use study were not available, any benefit suggested by the authors with terms such as "statin-induced risk reduction" or "statin-conferred benefits" are in question.

Table 4 in (1) shows that half the cardiac and all-cause death risk reduction disappears when available factors such as age and co-morbidity were adjusted for. The elephant in the room remains the unknown baseline cholesterol level that, if adjusted for, would likely remove any assumed mortality benefit, certainly in women (ref. 16 in (1)) and likely in older men as shown in placebo controlled studies (references in (4)).

1: Karp I, Chen S-F, Pilote L. Sex differences in the effectiveness of statins after myocardial infarction. CMAJ Jan. 30, 2007; 176 (3).

2. Anderson KM, Castelli WP, Levy D. Cholesterol and mortality. 30 years of follow-up from the Framingham study. JAMA. 1987 Apr 24;257(16):2176-80. Medline 3560398

3. Ulmer H, Kelleher C, Diem G, Concin H.  Why Eve is not Adam: prospective follow-up in 149650 women and men of cholesterol and other risk factors related to cardiovascular and all-cause mortality. J Womens Health (Larchmt). 2004 Jan-Feb;13(1):41-53. Medline 15006277

4. Vos E, Rose CP. Questioning the benefit of statins CMAJ Nov. 8, 2005; 173 (10). Medline 16275976.

Conflict of Interest:

None declared