Association of vitamin D with all-cause and cardiovascular disease mortality in COPD population: A cohort study from NHANES 2007-2018

Abstract

Background The correlation between low levels of vitamin D and an increased risk of various inflammatory diseases has been well established. However, the specific relationship between vitamin D levels and mortality in individuals suffering from chronic obstructive pulmonary disease (COPD) remains unclear. Therefore, the aim of this investigation was to explore the link between serum 25-hydroxyvitamin D [25(OH)D] concentrations and the probability of mortality from all causes and cardiovascular diseases (CVD) in American adults diagnosed with COPD. Methods A total of 1796 adults diagnosed with COPD, who participated in the National Health and Nutrition Examination Survey (2007–2018), were enrolled in this study. Data regarding deaths were obtained through linkage to the National Death Index (NDI) records until December 31, 2019. The association between 25(OH)D concentrations and the risk of mortality was examined both continuously using restricted cubic splines and categorically (< 25.0, 25.0–49.9, 50.0–74.9, and ≥ 75.0 nmol/L) through Cox regression modeling. Competing risk models were employed to explore the relationship between serum 25(OH)D levels and the incidence of CVD-related mortality in individuals diagnosed with COPD. Sensitivity and stratified analyses were conducted to assess the robustness of the findings. Results Over the course of the follow-up period, a total of 357 cases of all-cause mortality were observed, of which 85 were attributed to CVD-related causes. After accounting for various confounding factors, the study revealed that lower serum 25(OH)D levels were significantly associated with a heightened risk of all-cause and CVD-related mortality among COPD patients. When compared to individuals in the lowest category, those in the highest category of serum 25(OH)D showed a 52% reduction in all-cause mortality (HR: 0.48, CI [0.24, 0.94]) and a 69% increase in CVD-related mortality (HR: 0.31, CI [0.11, 0.84]). No evidence of a non-linear association between DII levels and all-cause mortality (p-non-linear = 0.1145) was found. Conclusions Our research indicates that among COPD patients, those with high serum vitamin D concentrations have a lower risk of all-cause and cardiovascular death compared to those with vitamin D deficiency. This demonstrates a non-linear negative correlation, supporting the long-term beneficial effect of vitamin D on COPD patients.