Grady 1991.

Methods	Randomised, double‐blind, placebo‐controlled trial using parallel group design (two intervention groups).
Participants	Country: United States. Number of participants randomised: 98 elderly ambulatory men and women (54%) women, aged 70 to 97 (mean 79.1) years of age. Inclusion criteria: elderly ambulatory men and women. Exclusion criteria: serum calcium levels of 2.57 mmol/L or more, urinary calcium levels of 7.28 mmol/day or more, creatinine clearance less than 0.42 mmol/s, history of hypercalcaemia, nephrolithiasis, seizure disorder, hyperparathyroidism, treatment with calcium, vitamin D or thiazide diuretics, and average calcium intake greater than 1000 mg/day.
Interventions	Participants were randomly assigned to receive: Intervention group 1: calcitriol (0.5 μg) daily (n = 50); Intervention group 2 (Control group): placebo vitamin D (n = 48); for a six‐month period.
Outcomes	The primary outcome measure was muscle strength.
Stated aim of study	"To test the hypothesis that the weakness associated with aging is in part due to inadequate serum concentrations of 1,25‐(OH2)D3."
Notes	"Participants were evaluated at 1, 2, 4, 8, 12, 18, and 24 weeks of intervention regimen to maintain compliance. Participants in both groups took more than 95% of the assigned medication." Calcitriol and placebo capsules were provided by Hoffman‐LaRoche (Nutley, NJ).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The trial is described as randomised but the method of sequence generation was not specified.
Allocation concealment (selection bias)	Unclear risk	The trial was described as randomised but the method used to conceal the allocation was not described, so that intervention allocations may have been foreseen in advance of, or during, enrolment.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	The trial was described as double blind, but the method of blinding was not described, so that knowledge of allocation was possible during the trial.
Incomplete outcome data (attrition bias) All outcomes	Low risk	The numbers and reasons for dropouts and withdrawals in all intervention groups were described.
Selective reporting (reporting bias)	Low risk	Pre‐defined, or clinically relevant and reasonably expected outcomes are reported on.
Industry bias	Unclear risk	Calcitriol and placebo capsules were provided by Hoffman‐LaRoche (Nutley, NJ).
Other bias	Low risk	The trial appears to be free of other components that could put it at risk of bias.