The Association of Vitamin D Deficiency, Age and Depression in US Adults: A Cross-Sectional Analysis

Abstract Background Depression is an important public health burden, vitamin D deficiency is associated with mood disorders. The risk of depression may increase with increasing age. Serum vitamin D levels and age are closely related. Objective This study is to investigate the association between vitamin D deficiency, age, and depression in a representative sample of US adults and the combined effect of vitamin D deficiency and aging on depression. Materials and Methods We extracted data from NHANES 2013–2018, including demographic characteristics, depression level, vitamin D level, physical activity, and body measures. Depression was screened by PHQ-9. Vitamin D was measured using the CDC method (test principle utilizing high performance liquid chromatography-tandem mass spectrometry to quantify 25OHD3, epi-25OHD3 and 25OHD2 in human serum). We performed binary logistic regression models to analyze the association between vitamin D, age and depression, respectively. Results A total of 15156 adults aged 20 years or older (mean age 49.81 ± 17.67 years, 7301 males and 7855 females) were included. Vitamin D levels were negatively associated with depression (P < 0.001). Vitamin D had a significant effect on depression (OR = 0.776, 95%Cl: 0.682–0.884, P < 0.001), the effect remained significant after adjusted for confounding variables (OR = 0.761, 95%Cl: 0.663–0.874, P < 0.001). Age was positively associated with depression (P < 0.001) and had a significant effect on depression (OR = 1.079, 95%Cl: 1.032–1.128, P = 0.001), the effect remained significant after adjusted for confounding variables (OR = 1.085, 95%Cl: 1.034–1.138, P = 0.001). Age and vitamin D levels were positively correlated (P < 0.001), and aging had a significant effect on vitamin D level (OR = 1.526, 95%Cl: 1.416–1.645, P < 0.001), the effect remained significant after adjusted for confounding variables (OR = 1.371, 95%Cl: 1.263–1.487, P < 0.001). In addition, the detection rate of depression was higher in females (2312/7855, 29.43%) than in males (1571/7301, 21.52%), and the difference was statistically significant (P < 0.001). Conclusions Vitamin D deficiency is a risk factor for depression; aging is a protective factor for vitamin D deficiency; Vitamin D and age synergetically affect the incident risk of depression: younger populations are more likely to present an increased risk of depression due to vitamin D deficiency; elderly females who are unmarried and living alone are the highest risk group for depression.