Prevention of depression and poor physical function in older persons with vitamin D supplementation

Depressive symptoms are common in older persons, often associated with poor
physical function and vitamin D deficiency (serum 25-hydroxyvitamin D < 50
nmol/l). Simple and cheap interventions to prevent depression are lacking.
Vitamin D deficiency occurs in 50% of persons >65 yr and has been associated
with an increase in depressive symptoms in many studies, as well as with
functional limitations and declining physical performance. A prior randomized
placebo-controlled trial on the effect of vitamin D supplementation in
overweight persons showed a decrease in depressive symptoms. Vitamin D
supplementation also had a positive influence on mobility tests in several
clinical trials. A mechanistic explanation is available: the vitamin D receptor
is present in muscle cells as well as in brain tissue, especially in the
hypothalamus. The hypothesis is that vitamin D decreases depressive symptoms
and improves physical performance and functional limitations in older persons.
Secondary hypotheses are that vitamin D decreases anxiety, improves cognitive
functioning and quality of life, and prevents the development of full-blown
depression in older persons.

Primary objectives:
1. Does vitamin D supplementation improve depressive symptoms in older persons?
2. Does vitamin D supplementation improve physical performance and functional
limitations in older persons?
Secondary objectives:
3. Does vitamin D supplementation decrease anxiety and improve cognitive
function and quality of life in older persons?
4. Can vitamin D supplementation prevent the development of full-blown
depression in older persons?
5. Is vitamin D supplementation a cost-effective strategy in the prevention of
increasing depressive symptoms and functional limitations and declining
physical performance?

A randomized double-blind placebo-controlled intervention study on the effect
of vitamin D 1200 IU per day versus placebo on depressive symptoms, physical
performance and functional limitations. The duration of intervention and
follow-up is one year.

The patients are randomized into two groups: vitamin D 1200 IU (three tablets
of 400 IU per day) or placebo (three tablets per day) for one year.

Potential participants are screened with postal questionnaires and a screening
visit to their general practice, a location near their home, or at their home
(short questionnaire and blood sample). After screening, they have to come 3
times to the general practice or location near their home (or receive home
visits) at baseline, after 6 and 12 months. They have to complete
questionnaires, perform physical performance tests, and a blood sample is drawn
twice at baseline and 6 months. Assessments at 3 weeks, 3 months and 9 months
are by telephone. The risk of the vitamin D treatment is negligible.