Reid 2006.

Study characteristics
Methods	RCT
Participants	Setting: Auckland, New Zealand N = 1471 Sample: women recruited by advertisement and mail‐outs using electoral rolls Age (years): mean 74.2 (SD 4.3) Inclusion criteria: consenting; aged > 55; more than 5 yr postmenopausal Exclusion criteria: free of major ongoing disease including serum creatinine > 1.8 mg/dl (0.2 mmol/litre), untreated hypo‐ or hyperthyroidism, liver disease, serum 25‐hydroxyvitamin D < 10 µg /litre (25 nmol/litre), malignancy, or metabolic bone disease; regular user in the previous year of hormone replacement therapy, anabolic steroids, glucocorticoids, or bisphosphonates; lumbar spine bone density below the age‐appropriate normal range (i.e. z‐score greater than ‐2)
Interventions	1. Intervention: calcium citrate 1 g/day in 2 divided doses 2. Control: identical placebo
Outcomes	1. Falls per person year reported 2. Number sustaining a fracture Other outcomes reported but not included in this review. Falls are a secondary outcome in this study
Duration of the study	5 years
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Treatments were allocated randomly using a minimization algorithm balancing for current thiazide use, age, and the occurrence of fractures resulting from minimal trauma after the age of 40 yr."
Allocation concealment (selection bias)	Low risk	Quote: "Subject numbers were allocated and medication was dispensed by staff who had no direct contact with the other study staff or the subjects."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	States "double blind" and "medication was dispensed by staff who had no direct contact with the other study staff or the subjects"
Blinding of outcome assessment (detection bias) Falls and fallers	Unclear risk	Insufficient information about ascertainment of falls to permit judgement
Blinding of outcome assessment (detection bias) Fractures	Low risk	States "double blind" and "medication was dispensed by staff who had no direct contact with the other study staff or the subjects". Subjects were asked at each 6‐month visit about fractures. If reported, the relevant radiograph or report was obtained.
Incomplete outcome data (attrition bias) Falls	Low risk	SeeAppendix 3 for method of assessment
Risk of bias in recall of falls	Unclear risk	"Subjects kept a diary of falls."  Details unclear.