Vitamin D has an immunomodulatory role. the aim of the present study is to assess the effect of vitamin D supplementation on exacerbation rate of COPD patient with a vitamin D deficiency.

Rationale: Although vitamin D is well known for its function in calcium homeostasis and bone mineralisation, several studies have shown immunomodulatory effects of vitamin D. Vitamin D deficiency is a common problem in patients with COPD..

Objective: To assess the effect of vitamin D supplementation on exacerbation rate in patients with COPD and a vitamin D deficiency.

Study design: Randomized, multi-center, double-blind, placebo-controlled intervention study.

Study population: 240 patients aged 40 years and older with COPD and a vitamin D deficiency (25-hydroxyvitamin D concentration(25OHD)<50 nmol/l) with a COPD exacerbation. An exacerbation is defined as sustained worsening of respiratory symptoms during 48 hours and requiring oral corticosteroid, antibiotic or combination treatment that was initiated by a physician. Respiratory symptoms include at least one of the Anthonisen criteria (increased dyspnoea, sputum volume or purulence). Patients with a severe vitamin D deficiency (25OHD<15 nmol/l), known osteoporosis and/or use of vitamin D supplementation > 400 IU per day will be excluded.

Intervention: Participants will be randomly allocated to receive vitamin D3 16800 IU or placebo orally once a week during 1 year.

Main study parameters/endpoints: The primary endpoint is exacerbation rate.

Follow-up of the study:

Recruitment of participants is more troublesome than expected due to several reasons, more use of vitamin D supplements, higher 250hydroxyvitamin D levels than anticipated, less suitability due to presence other exclusion criteria.

29/8/2017 total number recruited participants is 119

10/7/2018 closure of recruitment, total number recruited participants is 158

Inclusion Criteria:

• written informed consent
• aged above 40 years
• GOLD stages II-IV and diagnosis COPD confirmed by a medical doctor.
• minimum of 10 packyears of smoking
• vitamin D deficiency (a serum 25-hydroxyvitamin D lower than 50 nmol/l)
• ability to comply with all study requirements

Exclusion Criteria:

• pregnant or lactating women, or subjects who intend to become pregnant within the study period
• self-reported history of hypercalciemia or nephrolithiasis
• self-reported presence of sarcoidosis
• severe vitamin D deficiency (serum 25-hydroxyvitamin D lower than 15 nmol/l)
• life expectation of less than 6 months on the basis of concurrent disease
• interfering malignant diseases.
• diagnosed osteoporosis
• diagnosed asthma
• diagnosed chronic kidney disease stage 4 or higher (estimated glomerular filtration rate ≤ 29 ml/min/1,73 m2)
• serious mental impairment i.e. preventing to understand the study protocol or comply with the study aim; potentially unreliable patients and those judged by the investigator to be unsuitable for the study
• use of maintenance dose oral corticosteroids
• use of multivitamin supplement or vitamin D supplement which contains more than 400 IU per day
• current participation in a clinical rehabilitation programme