Porthouse 2005.

Study characteristics
Methods	Random allocation, initially 2:1 ratio intervention to control Remote site computer randomisation Blinding of outcome assessors not stated 3199 of 3314 completed
Participants	Multicentre general practice study, UK 3314 patients (all women), mean age 77 years, with at least 1 self‐reported risk factor for hip fracture Inclusion criteria: low body weight (< 58 kg), personal history of fracture, maternal history of hip fracture, current smoker, poor or fair health Disease exclusions: kidney or bladder stones, renal failure, hypercalcaemia, cognitive impairment, life expectancy < 6 months Drug exclusions: current calcium supplementation of > 500 mg/day
Interventions	1. Calcium 1000 mg and vitamin D3 800 IU given as 2 tablets daily, nurse gave general lifestyle advice, and information leaflet on calcium and vitamin D and on falls prevention Randomised 1321, completed 1269 2. Information leaflet on calcium and vitamin D and on falls prevention. Randomised 1993, completed 1930 Duration of treatment 18 to 42 months
Outcomes	Measured over a median follow‐up of 25 months (range 18 to 42 months) 1. Number of persons sustaining new hip fracture 2. Number of persons sustaining new non‐vertebral fracture 3. Number of persons dying
Notes	Prof DJ Torgerson provided pre‐publication report and further details 9‐16 February 2005
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	States "randomised"
Allocation concealment (selection bias)	Low risk	States "randomised (stratified by practice) by computer at the York Trials Unit by an independent person with no knowledge of the participants' characteristics"