Prevalence and correlates of vitamin D deficiency in adults after traumatic brain injury

O Jamall, C Feeney, J Zaw-Linn, A Malik, M Niemi, C Tenorio-Jimenez, T Ham, P Jenkins, G Scott, L Li, N Gorgoraplis, D  Baxter, DJ Sharp, A P Goldstone

Hammersmith Hospital, Imperial College.

Context: Traumatic brain injury (TBI) is a major cause of long-term disability with variable recovery. Pre-clinical studies suggest that vitamin D status may influence recovery after TBI. However, there is no published clinical data on links between vitamin D status and TBI outcomes.

Objectives: To determine the: (i) prevalence of vitamin D deficiency/insufficiency; and associations of vitamin D status with (ii) demographic factors and TBI severity, and (iii) cognitive function, symptoms and quality of life, in adults after TBI.

Design: Retrospective audit of patients seen in the Imperial multi-disciplinary TBI Clinic between July 2009 and March 2015. Serum vitamin D (25-hydroxy-cholecalciferol) was categorised as deficient (<40 nmol/L), insufficient (40-70 nmol/L) or replete (>70 nmol/L).

Patients: 353 adults (75.4% lighter-skinned ethnicity e.g. White Caucasian, 74.8% male, age median 35.1y, range 26.6-48.3y), range 0.3-56.5 months after TBI (74.5% moderate-severe according to Mayo classification).

Main Outcome Measure(s): Serum vitamin D concentrations; Addenbrooke’s Cognitive Examination (ACE-R), Beck Depression Inventory II (BDI-II), SF36 Quality of Life, Pittsburgh Sleep Quality Index.

Results: 46.5% of patients after TBI had vitamin D deficiency and 80.2% deficiency/insufficiency. Vitamin D concentrations were lower if taken during winter Daylight Saving Time (effect size mean ± SEM 13.2 ± 2.8 nmol/L), and in subjects of darker skin ethnicity (effect size 21.8 ± 2.8 nmol/L) in a 2-way ANOVA. Patients with vitamin D deficiency had worse cognitive function assessed by lower ACE-R scores than those who were vitamin D replete (effect size 4.5 ± 2.1, P=0.034), and higher BDI-II scores than those vitamin D insufficient (effect size 4.5 ± 1.6, P=0.003), correcting for age, gender, time since TBI and TBI severity. There was no association between vitamin D status and markers of TBI severity, sleep or quality of life (P>0.05).

Conclusion: Vitamin D deficiency is common in patients after TBI and is associated with impaired cognitive function and greater depressive symptoms.