We also performed
subgroup meta - analyses by type
of prevention (primary v secondary:
in this study, trials involving healthy populations or
patients with any specific disease except for cardiovascular disease were classified as primary prevention trials, and trials involving
patients with cardiovascular disease were classified as secondary prevention trials), type
of supplement by quality and dose (each supplement, vitamins only, antioxidants only, or antioxidants excluding vitamins), type
of outcome (cardiovascular death, angina, fatal or non-fatal myocardial infarction, stroke, or transient ischaemic attack), type
of outcome
in each supplement, type
of study design (randomised, double blind, placebo
controlled trial v open label, randomised
controlled trial), methodological quality (high v low), duration
of treatment (< 5 years v ≥ 5 years), funding source (pharmaceutical industry v independent organisation), provider
of supplements (pharmaceutical industry v not pharmaceutical industry), type
of control (placebo v no placebo), number
of participants (≥ 10000 v < 10000), and supplements given singly or
in combination with other vitamin or antioxidant supplements by quality.