Vitamin D status and cardiovascular disease. Observational studies in patients who underwent coronary angiography
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Background: Vitamin D is required to maintain a healthy cardiovascular system, but it is unknown whether variation in vitamin D status in the general population is physiologically relevant to development of cardiovascular diseases (CVDs).
Aim: To study vitamin D status and investigate the associations of vitamin D status with atherosclerosis progression, all-cause and CVD mortality.
Methods: Observational data from patients in Western-Norway with suspected coronary artery disease were used (n=4116). Vitamin D status was assessed by the measurement of plasma 25-hydroxyvitamin D (25OHD) concentrations, atherosclerosis progression by repeat coronary angiography and survival data obtained from national registries.
Results: Mean 25OHD most strongly associated with seasonality, adiposity and cod liver oil consumption. Seasonal variation in 25OHD differed by age. During winter and summer ~50% and ~80% of the participants were vitamin D sufficient, respectively. When modelling baseline values, cosinor models most accurately predicted follow-up values for patients with repeated measurements of 25OHD. Baseline concentrations of 25OHD were not associated with atherosclerosis progression after ~1 year of follow-up, but were inversely associated with a higher risk of all-cause and cardiovascular mortality after ~12 years of follow-up. Despite a linear tendency, non-linearity was observed in the relationship with all-cause mortality, with higher risk among individuals with 25OHD concentrations below 42.5 nmol/l and above 100 nmol/l in comparison to those between 42.5 – 100 nmol/l.
Conclusions: Seasonal variation has a strong influence on vitamin D status and researchers should consider cosinor models when adjusting for seasonality. A high frequency of insufficiency during winter indicates inadequate dietary intakes despite a high frequency of cod liver oil use in this population. Vitamin D status was inversely associated with a higher risk of all-cause and CVD mortality, but not associated with subclinical progression of atherosclerosis. The relationship with allcause mortality was J-shaped, with increased risk also among a smaller segment of participants with high 25OHD concentrations.