Title: Vitamin D and Longevity (ViDAL) trial - randomised feasibility study
Funder: Department of Health (England)

Abstract: DESIGN: Cluster randomisation of 20 participating GP practices in 10 matched pairs to inform the design of the main trial (10 to open randomisation between vitamin D3 or no treatment and 10 to double-blind randomisation between vitamin D3 or placebo).Feasibility trial on 1600 people (average 80 per practice) aged 65-84 with randomisation to 100000 IU vitamin D3 monthly (equivalent to 3300 IU/day) of oral vitamin D3 for 2 years (800 subjects) placebo (400 subjects) or no treatment (400 subjects).SETTING: 20 GP practices in England.TARGET POPULATION: Healthy adults 65-84 years of age. Exclusions: life-threatening illness planning to emigrate within 5 years known history of sarcoidosis hyperparathyroidism or nephrolithiasis known intolerance to vitamin D hypercalcaemia (corrected serum calcium >2.65 mmol/l) known hepatic or renal failure currently on cytotoxic therapy <3 years after diagnosis of any cancer. Informed consent for blood tests (including genetic analyses) and access to all written and electronic medical records and databases as well as randomisation and flagging for automatic follow-up.HEALTH TECHNOLOGY TO BE ASSESSED: 2.5mg (100000 IU) vitamin D3 taken monthly for 2 years randomised double blind v placebo (in 10 practices) or open label v no treatment (in 10 practices).MEASUREMENT OF COSTS AND OUTCOMES: Follow-up for cancer incidence and cause-specific mortality will be obtained by flagging through NHSCR. Incidence of other major diseases including diseases of the circulatory system will be obtained by NHS number linkage with Hospital Episode Statistics (HES). A postal questionnaire on foreign holidays sunbathing sunbed use and use of vitamin supplements is completed by all participants (treated and control) before randomisation. A blood sample is also taken and corrected serum calcium is assayed before randomisation to establish eligibility. Aliquots (plasma and buffy coat) are be stored in liquid nitrogen for later analysis of 25(OH)D and (subject to additional funding) genetic studies. A pack of 12 bottles is sent to all participants except the open control group at entry and at 1 year. To minimise follow-up costs subjects receiving medication (open label vitamin D unmarked vitamin D or unmarked placebo) are contacted 3-monthly by email text message or post (patient choice of medium) requesting a short reply by the same medium to confirm medication compliance and to report any/no suspected adverse events and any/no planned change of address. Non-compliers and those reporting adverse events or change of address are sent a short questionnaire (email or post) including validated questions on reasons for non-compliance and adverse events. All non-responders are sent one reminder a month later then telephoned if they have still not replied.A further blood sample and questionnaire will be obtained at the final GP visit 2 years after randomisation to quantify differences in vitamin D status between the intervention and control groups. GP records for the year before entry and the 2 years on the trial will also be extracted (GP visits prescriptions infections) on all patients.SAMPLE SIZE: We will recruit 1600 subjects (800 vitamin D 800 no treatment) through 20 GP practices. We assume that 80 (~9%) of the patients aged 65-84 in each GP practice will volunteer. The principal aims are to demonstrate feasibility in a representative range of GP practices and to determine the most cost-effective randomisation and follow-up procedures for the main study.


Research activity codes: 6.1 PHARMACEUTICALS
Health categories: GENERIC HEALTH RELEVANCE