Vitamin D Deficiency in children with disabilities: prevalence and determinants

Vitamin D is an essential pro-hormone for normal calcium homeostasis and bone
metabolism and plays an important role in muscle function and the immune
system. There is an increasing number of studies indicating that large numbers
of children and adults have inadequate vitamin D levels. Among the risk groups
for vitamin D deficiency are children with motor disabilities. It is well
established that prolonged deficiency of vitamin D can lead to muscle weakness
and muscle and bone pain and rickets. In 2012, the Dutch Health Council
recommended for all children daily vitamin D supplementation. It is unknown
whether parents of children with disabilities adhere to this advice and what
the prevalence of Vitamin D deficiency is among children with (motor)
disabilities. We hypothesize that children with (motor) disabilities are at
risk for vitamin D deficiency due to lower level of physical functioning and
reduced sun exposure due to less playing outside.

The primary objectives of the study are to investigate the vitamin D status of
Dutch children with motor disabilities attending a special needs school and to
associate Vit D status to the level of physical functioning, other potential
risk factors and symptoms.
Specific study aims are:
1. to investigate the prevalence of vitamin D insufficiecy and deficiency in
children with motor disabilities attending a special needs school;
2. to investigate the factors (level of physical functioning, diagnosis,
wheelchair dependency, skin type, dietary intake, comorbidity, medication use,
sun exposure) associated with a vitamin D insufficiency in this group of
children;
3. to investigate symptoms and complaints associated with a vitamin D
insufficiency in this group of children;

Vitamine D status of children with motor disabilities will be assessed at the
end of the winter season from blood sample obtained with a venipuncture (4ml).
Serum 25hydroxyvitamin D concentration will be measured. A questionnaire on
general health, complaints, medication use, skin type, dietary intake and
playing outside will be administered twice (October 2015 and February 2016) to
parents and children.

Children will undergo a venipuncture (superficial vein over the cubital fossa)
once (time investment 15 min). Parents and children will fill in a short
questionnaire twice (10 min each). Risks of venipuncture are pain due to
puncture and haematoma.