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Randomized Trials of Vitamin Supplements and Eye Disease

2014-08-27 04:00:16 | BioPortfolio

Summary

To determine whether vitamin E supplementation reduces the risk of cataract and age-related macular degeneration (AMD) in women.

To determine whether vitamin C supplementation reduces the risk of cataract and AMD in women.

To determine whether beta-carotene supplementation reduces the risk of cataract and AMD in women.

To determine whether alternate day, low-dose aspirin reduces the risk of cataract and AMD in women.

To identify potential risk factors for cataract and AMD including cigarette smoking, alcohol intake, blood pressure, blood cholesterol, cardiovascular disease, height, body mass index, and diabetes.

Description

Cataract and AMD are two of the most important causes of visual impairment in older Americans. Approximately 3.3 million people have visual impairment due to cataract. Cataract extraction, although one of the safest and most successful of all operations, is now the most frequently performed operation in the United States among persons older than 60, costing an estimated $1.5 billion annually. AMD is the leading cause of new cases of blindness in persons aged 65 and older. Approximately 25 percent of persons aged 65 years and older have signs of AMD. The pathogenesis of AMD, however, is only partly understood, and its etiology remains obscure. For most patients, there is no available treatment. The public health burden imposed by cataract and AMD will only increase in the coming decades as the U.S. population ages.

These randomized, double-masked, placebo-controlled trials will test the hypotheses that supplementation with antioxidant vitamins and with low-dose aspirin reduces the risk of age-related cataract and AMD. The study populations are the Women's Health Study (WHS) and the Women's Antioxidant Cardiovascular Study (WACS). The WHS is a randomized, double-masked, placebo-controlled trial using a 2x2 factorial design to test low-dose aspirin (100 mg on alternate days) and vitamin E (600 IU on alternate days) in the primary prevention of cardiovascular disease (CVD) and cancer. It is being conducted among 39,876 apparently healthy female health professionals age 45 years and older. The WACS is a randomized, double-masked, placebo-controlled secondary prevention trial using a 2x2x2x2 factorial design to test antioxidant vitamins (vitamins E [600 IU on alternate days] and C [500 mg daily], beta carotene [50 mg on alternate days]), and a combination of folate (800 mg daily), vitamin B6 (25 mg daily), and vitamin B12 (1 mg daily) among women who are at high risk for CVD morbidity and mortality. It is being conducted among 8,171 female health professionals, ages 40 years or older, who either have preexisting CVD or have at least three coronary risk factors and therefore are at high risk for the development of CVD.

In addition to the randomized comparisons, the investigators will also examine risk factors for age-related cataract and AMD in these two populations. Factors to be examined include cigarette smoking, alcohol intake, blood pressure, blood cholesterol, cardiovascular disease, height, body mass index, diabetes, and dietary factors.

In each study population, followup questionnaires were sent at 6 and 12 months after randomization and every 12 months thereafter requesting information about development of relevant study end points including cataract and AMD and participant compliance with study medications. Reported diagnoses of cataract and AMD are confirmed by medical record review. The primary analysis for the randomized studies will be incidence of AMD or cataract in the treatment and placebo groups. Survival analysis will be used to determine whether there is a difference in time to AMD or cataract diagnosis.

Study Design

Allocation: Randomized, Control: Placebo Control, Intervention Model: Factorial Assignment, Masking: Double-Blind, Primary Purpose: Prevention

Conditions

Macular Degeneration

Intervention

Aspirin, Beta-Carotene, Vitamin C, Vitamin E

Status

Active, not recruiting

Source

National Eye Institute (NEI)

Results (where available)

View Results

Links

Published on BioPortfolio: 2014-08-27T04:00:16-0400

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Medical and Biotech [MESH] Definitions

A lipid cofactor that is required for normal blood clotting. Several forms of vitamin K have been identified: VITAMIN K 1 (phytomenadione) derived from plants, VITAMIN K 2 (menaquinone) from bacteria, and synthetic naphthoquinone provitamins, VITAMIN K 3 (menadione). Vitamin K 3 provitamins, after being alkylated in vivo, exhibit the antifibrinolytic activity of vitamin K. Green leafy vegetables, liver, cheese, butter, and egg yolk are good sources of vitamin K.

A nutritional condition produced by a deficiency of VITAMIN D in the diet, insufficient production of vitamin D in the skin, inadequate absorption of vitamin D from the diet, or abnormal conversion of vitamin D to its bioactive metabolites. It is manifested clinically as RICKETS in children and OSTEOMALACIA in adults. (From Cecil Textbook of Medicine, 19th ed, p1406)

OXIDOREDUCTASES which mediate vitamin K metabolism by converting inactive vitamin K 2,3-epoxide to active vitamin K.

A form of MACULAR DEGENERATION also known as dry macular degeneration marked by occurrence of a well-defined progressive lesion or atrophy in the central part of the RETINA called the MACULA LUTEA. It is distinguishable from WET MACULAR DEGENERATION in that the latter involves neovascular exudates.

A family of phylloquinones that contains a ring of 2-methyl-1,4-naphthoquinone and an isoprenoid side chain. Members of this group of vitamin K 1 have only one double bond on the proximal isoprene unit. Rich sources of vitamin K 1 include green plants, algae, and photosynthetic bacteria. Vitamin K1 has antihemorrhagic and prothrombogenic activity.

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