Association of vitamin D and vitamin B12 with cognitive impairment in elderly aged 80 years or older: a cross-sectional study

Background The present study aimed to assess the association of vitamin D and vitamin B-12 with cognitive impairment in elderly people. Methods The data were obtained from a cross-sectional study that included individuals aged 80 years or older living in the urban and rural areas of the cities of Sideropolis and Treviso in the state of Santa Catarina, Brazil. In total, 165 elderly people were included in the analysis. The outcome of cognitive decline was assessed by the Mini-Mental State Examination. Vitamin D and vitamin B-12 levels were measured from blood samples. The socio-demographic, anthropometric and health variables used in the analysis were collected from a questionnaire. Crude and adjusted analyses of the relationship between vitamins D and B-12 and cognitive decline were performed using a Poisson regression model. Results The prevalence of cognitive decline was 35.2%. In the adjusted model, individuals who had vitamin D levels >19 ng mL(-1) showed a lower prevalence of cognitive decline (prevalence ratio = 0.59; 95% confidence interval = 0.39-0.87). Those participants who had vitamin B-12 levels of >= 496 pg mL(-1) had a higher prevalence of cognitive decline (prevalence ratio = 1.90; 95% confidence interval = 1.08-3.36). Conclusions The present study showed that individuals aged >= 80 years who had vitamin D levels of <= 18 ng mL(-1) had a higher prevalence of cognitive decline even after adjustment for potential confounders. In addition, the study demonstrated that vitamin B-12 levels of >= 496 pg mL(-1) in this population were also a risk factor for cognitive decline. A cross-sectional analysis does not enable the inference of a cause-effect relationship and additional studies are needed to understand these relationships.