Vitamin E May Protect Against Venous Thromboembolism in Women

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Vitamin E May Protect Against Venous Thromboembolism in Women

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September 12, 2007 — Women randomized to receive vitamin E

supplementation have a significant 21% reduction in incidence of

venous thromboembolism, according to results from the Women's Health

Study published online in the September 10 Publish Ahead of Print

issue of Circulation.

" Supplementation with vitamin E may antagonize vitamin K in healthy

adults, but it is unclear whether intake of vitamin E decreases the

risk of venous thromboembolism (VTE), " write J. Glynn, PhD,

ScD, from the Brigham and Women's Hospital at Harvard Medical School

in Boston, Massachusetts, and colleagues. " The Women's Health Study

tested whether vitamin E supplementation for 10 years decreased the

risk of cardiovascular disease or cancer in a large group of women

without these diseases at entry. We report here the effect of

randomized allocation to vitamin E or placebo on the occurrence of

VTE, a prospectively evaluated, secondary end point of this trial. "

In the Women's Health Study, 39,876 women aged 45 years or older were

randomized to receive 600 IU of natural source vitamin E or placebo on

alternate days. Blood samples drawn before randomization from 26,779

participants were used to determine factor V Leiden, G20210A

prothrombin, and 677C>T methylenetetrahydrofolate reductase (MTHFR)

polymorphisms.

Prospectively evaluated, secondary endpoints of the trial were

documented VTE, including deep vein thrombosis or pulmonary embolism,

and unprovoked VTE, defined as VTE in the absence of recent surgery,

trauma, or cancer diagnosis. The median follow-up period was 10.2 years.

Of 482 women who had VTE during follow-up, 213 were in the vitamin E

group and 269 were in the placebo group, yielding a significant 21%

hazard reduction (relative hazard, 0.79; 95% confidence interval [CI],

0.66 - 0.94; P = .010). The hazard reduction was 27% for unprovoked

VTE (relative hazard, 0.73; 95% CI, 0.57 - 0.94; P = .016).

Subgroup analyses showed that hazard reduction was 44% in the 3% of

participants who reported VTE before randomization (relative hazard,

0.56; 95% CI, 0.31 - 1.00; P = .048). In contrast, hazard reduction

was only 18% in women without prior VTE (relative hazard, 0.82; 95%

CI, 0.68 - 0.99; P = .040). For women with either factor V Leiden or

the prothrombin mutation, the hazard reduction associated with vitamin

E treatment was 49% (relative hazard, 0.51; 95% CI,

0.30 - 0.87; P = .014).

" These data suggest that supplementation with vitamin E may reduce the

risk of VTE in women, and those with a prior history or genetic

predisposition may particularly benefit, " the authors write. " The

estimated numbers of women who need to be treated with vitamin E for

10 years to prevent 1 VTE were 357 (95% CI, 200 to 1659) in the

overall population and 52 (95% CI, 32 to 144) in the high-risk

subgroup of women with a history of VTE or prothrombotic mutation. "

Study limitations include restriction to healthy and generally

health-conscious women, cautious interpretation required for secondary

endpoints in a trial, and inability to determine potential mechanisms

of action of vitamin E on risk for VTE.

" Overall, vitamin E may be a useful treatment for prevention of a

first or recurrent VTE, " the authors conclude. " Because VTE was a

prospectively evaluated, secondary end point of the Women's Health

Study, the protective effect observed here requires confirmation in

additional studies. Given its lack of efficacy for prevention of

cardiovascular disease and cancer, vitamin E may be most appropriate

for people at high risk of VTE. "

The National Institutes of Health funded this study. Roche Molecular

Systems, Inc, provided the genotyping platform used in this study. The

Natural Source Vitamin E provided vitamin E and vitamin E placebo.

Bayer Healthcare provided aspirin and aspirin placebo. The authors

have disclosed no relevant financial relationships.

Circulation. Published online September 10, 2007.