Background: Hypovitaminosis D is a frequent condition in elderly subjects. Vitamin D adequacy is best determined by measurement of the 25-hydroxyvitamin D-25(OH)D-concentration in the serum. An inverse association exists between 25(OH)D and cardiovascular, infectious, glucose metabolism, cognitive disorders, and all-cause mortality. Whether 25(OH)D is a marker of organ diseases is still under debate. We aimed to investigate whether comorbidities were associated with serum 25(OH)D levels in geriatric inpatients.
Methods: This is a retrospective study, including 237 subjects consecutively admitted to an acute care geriatric unit, with available data of 25(OH)D serum concentrations. 25(OH)D serum levels were defined according to the following cutoffs: 50⁻30 ng/mL (125⁻75 nmol/L): optimal range; 30⁻20 ng/mL (75⁻50 nmol/L): insufficiency; 20⁻10 ng/mL (5⁻25 nmol/L): deficiency; and <10 ng/mL (<25 nmol/L): severe deficiency. Comorbidity was assessed using the Cumulative Illness Rating Scale-Geriatric (CIRS-G). Two summary measures were obtained, the Illness Severity Index (CIRS-SI) and the Comorbidity Index (CIRS-CI).
Results: 177 (74.68%) women and 60 (25.32%) men with mean age of 85 ± 6 years old were enrolled. The majority of subjects (68.6%) were at risk of malnutrition. Overall, the burden of comorbidity was 1.87 ± 1.33 for CIRS-CI and 1.18 ± 0.40 for CIRS-SI. 25(OH)D serum concentrations were 10.58 ± 7.68 ng/mL, with 98.7% of subjects having vitamin D below 30 ng/mL and 56.6% with severe deficiency. An inverse correlation was found between 25(OH)D and both CIRS-SI (r: -0.312; p < 0.0001) and CIRS-CI (r: -0.306; p < 0.0001). Independent of multiple covariates an inverse association between both CIRS-SI (p < 0.0001) and CIRS-CI (p < 0.0001) and 25(OH)D was confirmed. Both CIRS-SI (r = 0.251, p < 0.0001) and CIRS-CI (r = 0.137, p = 0.016) were positively correlated with the length of hospital stay. An inverse correlation was confirmed between serum 25(OH)D concentrations and CRP (r = -0.142; p = 0.041). CRP, in turn, positively correlated with CIRS-SI (r = 0.209, p = 0.003) and CIRS-CI (r = 0.158, p = 0.023). Both CIRS-SI (r = 0.251, p < 0.0001) and CIRS-CI (r = 0.137, p = 0.016) were positively correlated with the length of hospital stay.
Conclusions: In hospitalized very old subjects, a higher comorbidity burden is associated with lower 25(OH)D serum levels. Hypovitaminosis D was correlated with higher inflammatory status, which, together with the comorbidities burden, negatively influenced the length of hospital stay.
Keywords: biomarkers; geriatric assessment; hospital-related; malnutrition; multimorbidities; vitamin D.