Vitamin D status of patients admitted to a hospital rehabilitation unit: relationship to function and progress

The primary objective was to determine the association between vitamin D status, baseline function, and short-term inpatient rehabilitation progress.

This was a prospective convenience sampling of 100 patients in a tertiary general hospital rehabilitation unit (RU). The cohort comprised men and women of mixed race with a variety of diagnoses (mean age 70 yrs). Patient histories and demographic information were obtained by patient interview and chart review. Serum 25-hydroxyvitamin D (25OHD) (nmol/L) was measured on or after the day of admission. The Functional Independence Measurement (FIM) instrument, a validated survey tool, was used to measure function at admission and discharge.

Eleven percent of the patients were overtly vitamin D deficient, with serum 25OHD concentrations <20 nmol/L. Ninety-four percent of the patients had serum 25OHD concentrations below the recommended minimum optimal concentration of 80 nmol/L. Using the Spearman rank correlation test, low serum 25OHD was weakly but significantly associated with low total FIM scores: r = 0.25 (P < 0.012) and r = 0.23 (P < 0.021) for admission and discharge total FIM score, respectively. Patients with serum 25OHD concentrations greater than the median value of 41.3 nmol/L had significantly higher FIM efficiency scores (discharge total FIM score - admission total FIM score/length of stay [LOS]) than the subgroup of patients below the median (2.0 +/- 1.1 vs. 1.6 +/- 0.9, respectively; P < or = 0.026). Serum 25OHD was not significantly correlated with FIM efficiency or the unadjusted change in total FIM score (discharge total FIM score - admission total FIM score), but it was significantly correlated with LOS (the lower the serum 25OHD concentration, the longer the LOS, and vice versa; r = -0.235, P < 0.018). Thus, the difference in FIM efficiency between patients with serum 25OHD above and below the median was the result of the significant inverse correlation between serum 25OHD and LOS; as a group, patients with serum 25OHD above the median had a 19% shorter LOS than the group with serum 25OHD below the median value (11.4 +/- 4.9 vs. 14.1 +/- 5.6 days, respectively; P = 0.005).

Most patients in a hospital RU had a suboptimal serum 25OHD concentration, reflecting what has previously been observed in hospitalized patients in general and also the population at large. Although no specific physical deficits or attributes could be directly attributed to low serum 25OHD, the baseline functional status of RU patients, LOS, and progress attributable to inpatient rehabilitation (FIM efficiency) were favorably affected by higher serum 25OHD concentrations.