Background Serum vitamin D deficiency is common in the patients with cardiovascular disease (CVD), but the association between serum vitamin D levels and risk of all-cause mortality in patients with CVD is controversial. Objective This study aimed to understand better the association between serum 25(OH)D status and risk of all-cause mortality in patients with prior CVD. Method We conducted a cohort study using data from the National Health and Nutrition Examination Survey from 2007 to 2018 to investigate the association between serum 25(OH)D and the risk of all-cause mortality using multivariate Cox regression models, with further subgroup analyses and interactions smooth curve fitting to address possible nonlinearities. Result A total of 3220 participants with prior CVD were included in this study, with a total of 930 deaths over a median follow-up of 5.52 years, with multivariable-adjusted serum vitamin D levels after natural log transformation (4.31–4.5 ) as a reference in COX regression, and corrected HRs and 95% CIs of 1.81 (1.31, 2.50), 1.34 (1.07, 1.66), 1.28 (1.05, 1.56),1.00 (reference), 1.10 (0.89, 1.37) for all-cause mortality, respectively. Results remained robust in the stratified analysis of interactions, but a L-shaped relationship was detected. We identified an inflection point of 4.5 after multivariate adjustment through a two-stage linear regression model and recursive algorithm. Conclusion Our findings demonstrate that increasing serum 25(OH)D levels may have a L-shaped relationship with risk of all-cause mortality and that increases in serum 25(OH)D levels do not continue to reduce the risk of all-cause mortality.
Background Serum vitamin D deficiency is common in the patients with cardiovascular disease (CVD), but the association between serum vitamin D levels and risk of all-cause mortality in patients with CVD is controversial. Objective This study aimed to understand better the association between serum 25(OH)D status and risk of all-cause mortality in patients with prior CVD. Method We conducted a cohort study using data from the National Health and Nutrition Examination Survey from 2007–2018 to investigate the association between serum 25(OH)D and the risk of all-cause mortality using multivariate Cox regression models, with further subgroup analyses and interactions smooth curve fitting to address possible nonlinearities. Result A total of 3220 participants with prior CVD were included in this study, with a total of 930 deaths over a median follow-up of 5.52 years, with multivariable-adjusted serum vitamin D levels (< 25 nmol/L) as a reference in COX regression, and corrected HRs and 95% CIs of 1.00 (reference), 0.74 (0.55, 1.00), 0.69 (0.51, 0.93), and 0.58 (0.43, 0.79) for all-cause mortality, respectively. Results remained robust in the stratified analysis of interactions, but a U-shaped relationship was detected. We identified an inflection point of 89.8 nmol/L after multivariate adjustment through a two-stage linear regression model and recursive algorithm. Conclusion Our findings demonstrate that increasing serum 25(OH)D levels may have a U-shaped relationship with risk of all-cause mortality and that increases in serum 25(OH)D levels do not continue to reduce the risk of all-cause mortality beyond specific criteria have a diminished protective effect.
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