Association between serum concentration of vitamin D and 1-year mortality in stroke patients

The prevalence of 25-hydroxyvitamin D [25(OH)D] deficiency is high in patients presenting with an acute stroke, and it may be associated with greater clinical severity and a poor early functional prognosis. However, no data about its impact on long-term prognosis is available. In this study, we aimed to assess the association between 25(OH)D levels and 1-year mortality in stroke patients.

From February to December 2010, 382 Caucasian stroke patients admitted to the Department of Neurology of the University Hospital of Dijon, France, were enrolled prospectively. Demographics and clinical information including stroke severity assessed using the National Institutes of Health Stroke Scale score were collected. The serum concentration of 25(OH)D was measured at baseline. Multivariable Cox regression models were used to evaluate the association between 1-year all-cause mortality and serum 25(OH)D levels treated as either a log-transformed continuous variable or dichotomized (<25.7 and ≥25.7 nmol/l) at the first tertile of their distribution.

Of the 382 stroke patients included, 63 (16.5%) had died at 1 year. The mean 25(OH)D level was lower in these patients (32.3 ± 22.0 vs. 44.6 ± 28.7 nmol/l, p < 0.001), and survival at 1 year was worse in patients in the lowest tertile of 25(OH)D levels (defined as <25.7 nmol/l); log-transformed 25(OH)D levels were inversely associated with 1-year mortality (hazard ratio, HR = 0.62; 95% confidence interval, 95% CI: 0.44-0.87; p = 0.007), and patients with 25(OH)D levels <25.7 nmol/l were at a higher risk of death at 1 year (HR = 1.95; 95% CI: 1.14-3.32; p = 0.014). In multivariable analyses, the association was no longer significant but a significant interaction was found for age, and stratified analyses by age groups showed an inverse relationship between 25(OH)D levels and 1-year mortality in patients aged <75 years [HR = 0.38; 95% CI: 0.17-0.83; p = 0.015 for log-transformed 25(OH)D levels, and HR = 3.12; 95% CI: 0.98-9.93; p = 0.054 for 25(OH)D levels <25.7 vs. >25.7 nmol/l].

A low serum 25(OH)D level at stroke onset may be associated with higher mortality at 1 year in patients <75 years old. Further studies are needed to confirm these findings and to determine whether vitamin D supplementation could improve survival in stroke patients.