A recent study published by the journal Archives of Physical Medicine and Rehabilitation found that low vitamin D status acts as an independent predictor for decreased functional independence and physical activity in patients with chronic spinal cord injury (SCI).
The spinal cord is comprised of a large group of nerves housed in the center of the spine, which carries messages between the brain and the rest of the body. When an individual experiences a SCI, symptoms may include a loss of muscle function, lack of sensation and paralysis. Due to the decreased sensation and movement, muscle wasting and disability results. Therefore, SCI patients lose functional independence in activities of daily living (ADL) and they experience decreased performance in leisure time physical activity (LTPA).
Vitamin D plays an important role in muscle function. In fact, research has determined that vitamin D helps improve muscle strength by increasing the rate of protein synthesis and enlarging muscle fiber size. Furthermore, researchers have discovered that vitamin D may help improve nerve regeneration and increase nerve fiber size in animal models.
According to a past study, up to 94% of patients with SCI are vitamin D deficient. This is likely due to a variety of contributing factors, including comorbidities such as obesity inadequate sun exposure and the use of medications that may affect vitamin D metabolism. However, no research has examined the relationship between vitamin D status and physical function in patients with SCI.
Therefore, researchers recently aimed to determine if vitamin D status is associated with functional independence in relation to ADL and LTPA. The study included a total of 100 patients with trauma related SCI who were admitted to a rehabilitation program at the Spinal Unit of San Raffaele Institute of Sulmona. Patients were excluded from the study if they supplemented with vitamin D, exhibited neurological or cognitive deficits or had severe comorbidities.
All patients received a thorough neurological examination, body weight assessment and a serum 25(OH)D analysis. Their SCI related pain was assessed using a standard numerical scale based on the National Institute on Disability and Rehabilitation Research recommendations. Functional independence in ADL was measured by the spinal cord independence measure (SCIM), which is a standard instrument used to rate SCI patient’s ability to perform everyday tasks without assistance. A low rating indicates a stronger degree of dependence. Overall physical function was determined using the LTPA Questionnaire for people with Spinal Cord Injury (LTPAQ-SCI). This self-administered questionnaire allows researchers to quantify the patient’s perceived psychophysical effort.
Did the researchers find a relationship between vitamin D status and functional independence in relation to ADL and LTPA? Here is what they found:
- A total of 78% of patients were vitamin D deficient (<20 ng/ml; 50 nmol/l), and 18% were vitamin D insufficient (20-29 ng/ml; 50-72.5 nmol/l).
- The vitamin D deficient individuals had a significantly elevated body mass index (p = 0.02), decreased functional independence in ADL (p = 0.002) and diminished weekly LTPA involvement (p = 0.03).
- After adjusting for other predictors of physical function outcomes, the researchers found that lower vitamin D levels were independently associated with decreased functional independence in ADL (p < 0.0001) and poorer LTPA (p = 0.004).
The researchers concluded,
“In people with chronic SCI, a low vitamin D level represents an independent predictor of poor physical function.”
This study is the first to evaluate the role of vitamin D in physical function in patients with trauma related SCIs. Although successfully confirming their hypothesis, as always, it is important to note the study’s limitations. Due to the cross sectional design, researchers cannot definitely determine whether vitamin D is a predictor or a result of this condition. The study also had a relatively small sample size, thereby decreasing the strength of their findings.
With 96% of the study population either vitamin D insufficient or deficient, individuals with SCI are in need of further research to determine the possible clinical implications of this widespread deficiency. The researchers recommend future intervention trials to determine whether vitamin D supplementation may improve physical function in patients with SCI.
Sturges, M. & Cannell, JJ. Is vitamin D status is a predictor of muscle function in patients with chronic spinal cord injury? The Vitamin D Council Blog & Newsletter. February, 2016.