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Fall Prevention: how much vitamin D do you need?
 
 
  "Achieved serum 25(OH)D concentrations of 60 nmol/l or more resulted in a 23% fall reduction (pooled relative risk 0.77, 95% CI 0.65 to 0.90), whereas concentrations of less than 60 nmol/l had no effect on number of falls (pooled relative risk 1.35, 95% CI 0.98 to 1.84)"
 
"Vitamin D has a direct beneficial effect on muscle, and improved strength and balance in several trials in older persons"
 
"Each year one in three people aged 65 years or older experiences at least one fall,1 2 3 with 9% of falls leading to an emergency room visit and 5-6% resulting in a fracture.....Vitamin D has direct effects on muscle strength modulated by specific vitamin D receptors present in human muscle tissue.5 6 Myopathy (myopathy from HIV or ART may play a role in increasing risk in HIV+) from severe vitamin D deficiency presents as muscle weakness and pain,7 but is reversible with vitamin D supplementation.6 In several trials of older individuals at risk for vitamin D deficiency, vitamin D supplementation improved strength, function, and balance in a dose-related pattern.4 8 9 Most importantly, these benefits translated into a reduction in falls"
 
"In this meta-analysis of eight double blind randomised controlled trials, the efficacy of supplemental vitamin D for fall prevention depended on dose and achieved 25(OH)D concentrations among individuals aged 65 years and older. No fall reduction was observed for a daily dose of less than 700 IU vitamin D or achieved serum 25(OH)D concentrations below 60 nmol/l. Daily vitamin D doses in the range of 700 IU to 1000 IU or achieved serum concentrations between 60 nmol/l and 95 nmol/l reduced the risk of falling by 19%. Given the absence of data beyond these beneficial ranges, our analyses don't preclude the possibility that higher doses of vitamin D or higher achieved 25(OH)D concentrations would have been even more efficient in reducing falls. At the high dose range of 700 IU to 1000 IU a day, the benefit of vitamin D was not significantly affected by type of supplemental vitamin D, gender, age, or level of independence. Notably, fall prevention with a high dose might not depend on additional calcium supplementation and was attained with treatment for less than 12 months (2-5 months). The benefit was sustained for 12-36 months."
 
"Conclusions: Doses of 700 IU to 1000 IU supplemental vitamin D a day could reduce falls by 19% or by up to 26% with vitamin D3. This benefit may not depend on additional calcium supplementation, was significant within 2-5 months of treatment, and extended beyond 12 months of treatment. Conversely, our results do not support the clinical use of vitamin D doses below 700 IU a day for the prevention of falls among older individuals. A 25(OH)D concentration of at least 60 nmol/l is required for fall prevention; therefore, a daily intake of at least 700 IU supplemental vitamin D is warranted in all individuals age 65 and older. Notably, good adherence is essential as the effect of vitamin D on falls will not be proportional below 700 IU a day. Furthermore, it is possible that greater benefits may be achieved with the use of vitamin D3 instead of vitamin D2. Finally, active forms of vitamin D do not appear to be more effective than 700-1000 IU of supplemental vitamin D for fall prevention in older persons."
 
"In subgroup analyses of the trials that assessed a high dose of supplemental vitamin D (700-1000 IU), the pooled relative risk reduction was 12% in trials that used vitamin D2 compared with 26% for trials that used vitamin D3 (P=0.28; table 2). The combined effect of calcium plus vitamin D compared with placebo in one study showed a relative risk reduction of 19%.w2 The main effect of vitamin D, either vitamin D compared with placebo or vitamin D plus calcium compared with calcium only, was tested in six studies. The pooled relative risk reduction for these six studies was 23% (relative risk 0.77, 95% CI 0.65 to 0.92); thus, the main effect of vitamin D may not depend on additional calcium supplementation"

 
Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials

 
Published 1 October 2009, doi:10.1136/bmj.b3692
Cite this as: BMJ 2009;339:b3692
 
H A Bischoff-Ferrari, director of centre on aging and mobility1,2, B Dawson-Hughes, director of bone metabolism laboratory3, H B Staehelin, professor emeritus 4, J E Orav, associate professor of biostatistics5, A E Stuck, professor of geriatrics6, R Theiler, head of rheumatology7, J B Wong, professor of medicine 8, A Egli, fellow1, D P Kiel, associate professor of medicine9, J Henschkowski, fellow1,6
 
1 Centre on Aging and Mobility, University of Zurich, Switzerland, 2 Department of Rheumatology and Institute of Physical Medicine, University Hospital Zurich, Switzerland, 3 Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA, 4 Department of Geriatrics, University Hospital Basel, Switzerland, 5 Department of Biostatistics, Harvard School of Public Health, Boston, MA, USA, 6 Department of Geriatrics, Inselspital and Spital Netz Bern Ziegler, University of Bern, Switzerland, 7 Department of Rheumatology, Triemli Hospital, Zurich, Switzerland, 8 Division of Clinical Decision Making, Tufts Medical Center, Boston, MA, USA, 9 Hebrew Senior Life Institute for Aging Research, Harvard Medical School, Boston, MA, USA
 
Correspondence to: H A Bischoff-Ferrari, University Hospital Zurich, Gloriastrasse 25, 8091 Zurich, Switzerland heike.bischoff@usz.ch
 
Abstract
 
Objective - To test the efficacy of supplemental vitamin D and active forms of vitamin D with or without calcium in preventing falls among older individuals.
 
Data sources - We searched Medline, the Cochrane central register of controlled trials, BIOSIS, and Embase up to August 2008 for relevant articles. Further studies were identified by consulting clinical experts, bibliographies, and abstracts. We contacted authors for additional data when necessary.
 
Review methods - Only double blind randomised controlled trials of older individuals (mean age 65 years or older) receiving a defined oral dose of supplemental vitamin D (vitamin D3 (cholecalciferol) or vitamin D2 (ergocalciferol)) or an active form of vitamin D (1{alpha}-hydroxyvitamin D3 (1{alpha}-hydroxycalciferol) or 1,25-dihydroxyvitamin D3 (1,25-dihydroxycholecalciferol)) and with sufficiently specified fall assessment were considered for inclusion.
 
Results - Eight randomised controlled trials (n=2426) of supplemental vitamin D met our inclusion criteria. Heterogeneity among trials was observed for dose of vitamin D (700-1000 IU/day v 200-600 IU/day; P=0.02) and achieved 25-hydroxyvitamin D3 concentration (25(OH)D concentration: <60 nmol/l v ≥60 nmol/l; P=0.005). High dose supplemental vitamin D reduced fall risk by 19% (pooled relative risk (RR) 0.81, 95% CI 0.71 to 0.92; n=1921 from seven trials), whereas achieved serum 25(OH)D concentrations of 60 nmol/l or more resulted in a 23% fall reduction (pooled RR 0.77, 95% CI 0.65 to 0.90). Falls were not notably reduced by low dose supplemental vitamin D (pooled RR 1.10, 95% CI 0.89 to 1.35; n=505 from two trials) or by achieved serum 25-hydroxyvitamin D concentrations of less than 60 nmol/l (pooled RR 1.35, 95% CI 0.98 to 1.84). Two randomised controlled trials (n=624) of active forms of vitamin D met our inclusion criteria. Active forms of vitamin D reduced fall risk by 22% (pooled RR 0.78, 95% CI 0.64 to 0.94).
 
Conclusions Supplemental vitamin D in a dose of 700-1000 IU a day reduced the risk of falling among older individuals by 19% and to a similar degree as active forms of vitamin D. Doses of supplemental vitamin D of less than 700 IU or serum 25-hydroxyvitamin D concentrations of less than 60 nmol/l may not reduce the risk of falling among older individuals.
 
Introduction
 
Each year one in three people aged 65 years or older experiences at least one fall,1 2 3 with 9% of falls leading to an emergency room visit and 5-6% resulting in a fracture.4 Fall prevention has, therefore, become a public health goal, especially as the older proportion of the population grows.
 
Vitamin D has direct effects on muscle strength modulated by specific vitamin D receptors present in human muscle tissue.5 6 Myopathy from severe vitamin D deficiency presents as muscle weakness and pain,7 but is reversible with vitamin D supplementation.6 In several trials of older individuals at risk for vitamin D deficiency, vitamin D supplementation improved strength, function, and balance in a dose-related pattern.4 8 9 Most importantly, these benefits translated into a reduction in falls.4 8 9
 
Overall, however, results have been mixed for fall prevention with vitamin D; for example, several trials of vitamin D have had non-significant results. This may be explained in part by the use of low doses of vitamin D, as suggested by a 2004 meta-analysis of limited data from three trials on supplemental vitamin D.10 Other potential explanations include the availability of vitamin D over the counter for the control group; the use of an open trial design, which biases trial results towards the null11; and incomplete assessment, inadequate definition, or incomplete ascertainment of falls during the entire observation period,12 again introducing a bias towards the null.
 
Several trials on vitamin D have been performed since 2004; thus, the importance of vitamin D dose for the prevention of falls should be reassessed. Specifically, we need to establish the optimum threshold of serum 25-hydroxyvitamin D3 (25(OH)D; calcidiol (25-hydroxycholecalciferol)) required to prevent falls in older individuals. Notably, two epidemiology studies among older individuals have found a dose-response relationship between lower extremity function and serum 25(OH)D concentrations,13 14 with one study identifying a threshold of 50 nmol/l for optimal function.13 The other larger study found that function continued to improve with increasing concentration, without any plateau.14
 
Both active forms of vitamin D and standard supplemental vitamin D have been suggested to prevent falls among older individuals, but no direct comparison of these two groups is available. Active forms of vitamin D do not need hydroxylation in the kidney, so their effect on falls should be influenced less by age related decline in kidney function than the effect of supplemental vitamin D. However, active forms of vitamin D cost more and are associated with a higher risk for hypercalcaemia than standard supplemental vitamin D.
 
The aim of this meta-analysis was to assess the efficacy of vitamin D supplementation, with and without calcium, for the prevention of falls among older persons by dose and serum concentration of 25(OH)D achieved. In addition, we assessed the efficacy of active forms of vitamin D compared with supplemental vitamin D in the prevention of falls.
 
Results
 
A total of 164 articles were found in our initial search, 132 of which could be excluded by screening the titles and abstracts (fig 1). A further 12 articles were excluded either because they did not detail randomised controlled trials or they were review articles. Ten more trials were excluded because they did not meet the inclusion criteria so that 10 randomised trials were included in the final analysis-eight that studied either vitamin D2 or vitamin D3 and two that assessed active forms of vitamin D.
 
Trials assessing supplemental vitamin D
We identified eight randomised controlled trials of supplemental vitamin D that met our inclusion criteria (box 1).w1-w8 All trials assessed vitamin D treatment for the prevention of falls as a primary or secondary outcome and were identified through our MeSH term search. One study consisted of a multiple dose trial in which the authors provided additional data for the four trial arms (200, 400, 600, and 800 international units (IU) D2 v placebo).w1
 
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1 Fall ascertainment in trials with supplemental vitamin D included in the primary analysis
 
Broe et al, 2007w1
Falls were defined as "a sudden, unintentional change in position causing a resident to fall on the ground." Nursing staff filled out an incident report at the time of the event, the primary care physician verified it, and the information was entered into the incident report database.
 
Bischoff-Ferrari et al, 2006w2
Falls were defined as "unintentionally coming to rest on the ground, floor, or other lower level." Participants were asked to send a postcard after every fall, which was then followed by a telephone call from a staff member to assess the circumstances of the fall. In addition, falls were ascertained at every follow-up visit (every six months).
 
Prince et al, 2008w3
Falls were defined as "unintentionally coming to rest on the ground, floor, or other lower level." Patients were interviewed by study staff every six weeks via telephone or during clinic visits. The number of falls that had occurred in the previous six weeks and the associated features of the falls were recorded on a questionnaire.
 
Flicker et al, 2005w4
Falls were defined as "an event that results in a person coming to rest inadvertently on the ground or other lower level." Residential care staff recorded falls continuously in diaries, and these were mailed monthly to the central study centre.
 
Pfeifer et al, 2008w5
A fall was defined as "falling on to the floor or ground, or hitting an object like a chair or stair." Not included as falls were controlled or intentional movements towards a chair or bed or a near fall in which the participant caught oneself before falling on to the floor or ground. The number of falls was recorded in fall diaries-each day the participants had to make a cross in the diary depending on whether a fall had occurred or not. Every two months, the study participants were also asked via telephone interviews whether a fall had happened.
 
Bischoff et al, 2003w6
Falls were defined as "unintentionally coming to rest on the ground, floor, or other lower level." Coming to rest against furniture or a wall was not counted as a fall. Falls were recorded by nurses on the inpatient units who had received training in the use of the fall protocol (which included recording date, time, circumstances, and injuries).
 
Pfeifer et al, 2000w7
A fall was defined as "falling on to the floor or ground or hitting an object like a chair or stair." Not included as falls were controlled or intentional movements toward a chair or bed or a near fall in which the participant caught herself before falling on to the floor or ground. The number of falls was recorded by questionnaires throughout the trial period.
 
Graafmans et al, 1996w8
A fall was defined as "unintentionally coming to rest at a lower level or on the ground." Participants were asked to record in a diary any falls they had during a 28-week period. Every week, participants registered whether or not they had fallen, as well as the location, time, and circumstances of each fall.
 
--------------------------------
 
Table 1 shows the characteristics of the eight double blind randomised controlled trials with sufficient fall assessment included in our study, including one randomised controlled trial with four study arms.w1 The eight trials involved 2426 individuals in total, 81% of whom were women, and participants had an approximate mean age of 80 years. All participants were in stable health and were living in the community or in nursing homes. Vitamin D3 was used in five studies and vitamin D2 in three studies. Vitamin D2 or D3 was given in a daily dose ranging from 200 IU to 1000 IU. Treatment duration varied from 2 months to 36 months. Calcium supplementation was used in both treatment and placebo groups in five randomised controlled trials, and the dose varied between 500 mg/day and 1200 mg/day. In one study, calcium was provided only in the treatment group, and vitamin D alone was compared with placebo in two trials. Adherence varied between 68% and 100%, with seven out of eight trials reporting adherence of 80-100%.
 
Fall prevention with oral supplemental vitamin D
In the eight randomised controlled trials, the pooled relative risk for any dose of vitamin D preventing a fall was 0.87 (95% CI 0.77 to 0.99). However, heterogeneity in results was seen among studies (Q test: P=0.05), although this was resolved after stratifying trials by daily dose (200-600 IU v 700-1000 IU).
 
The pooled relative risk for the seven studies with 700-1000 IU supplemental vitamin D a day (1921 individuals) was 0.81 (95% CI 0.71 to 0.92) suggesting that a high dose of vitamin D a day reduced the risk of a person falling by 19% (table 2, fig 2). The pooled risk difference for the high dose was 9.4% (95% CI 5.1% to 13.7%; P<0.0001), so the number needed to treat was 11 (95% CI 7 to 20) for a treatment duration of 2-36 months.
 
The pooled relative risk for the two trials with a dose of less than 700 IU (200-600 IU) vitamin D a day was 1.10 (95% CI 0.89 to 1.35; Q test: P=0.42) indicating that less than 700 IU vitamin D a day did not reduce fall risk (table 3, fig 2).
 
Achieved serum 25(OH)D concentrations of 60 nmol/l or more resulted in a 23% fall reduction (pooled relative risk 0.77, 95% CI 0.65 to 0.90), whereas concentrations of less than 60 nmol/l had no effect on number of falls (pooled relative risk 1.35, 95% CI 0.98 to 1.84).
 
Figure 3 shows the relationship between vitamin D and falls, and suggests that fall prevention begins with a daily dose of 700 IU supplemental vitamin D. This threshold was confirmed in a meta-regression of 2426 individuals, in which a significant inverse relationship was found between dose and the risk of sustaining at least one fall (beta estimate for dose: ≥700 IU v <700 IU=0.337; P=0.02). Figure 3 also suggests that a 25(OH)D concentration of 60 nmol/l is required for fall prevention. This possibility was likewise confirmed by a meta-regression of 1447 individuals (two trials did not provide 25(OH)D dataw4 w8), which indicated a significant inverse relationship between 25(OH)D serum concentration and the risk of sustaining at least one fall (beta estimate for 25(OH)D concentration: ≥60 nmol/l v <60 nmol/l=0.586; P=0.005).
 
Primary subgroup analyses with trials assessing high doses of supplemental vitamin D
 
In subgroup analyses of the trials that assessed a high dose of supplemental vitamin D (700-1000 IU), the pooled relative risk reduction was 12% in trials that used vitamin D2 compared with 26% for trials that used vitamin D3 (P=0.28; table 2). The combined effect of calcium plus vitamin D compared with placebo in one study showed a relative risk reduction of 19%.w2 The main effect of vitamin D, either vitamin D compared with placebo or vitamin D plus calcium compared with calcium only, was tested in six studies. The pooled relative risk reduction for these six studies was 23% (relative risk 0.77, 95% CI 0.65 to 0.92); thus, the main effect of vitamin D may not depend on additional calcium supplementation. The effect of vitamin D in women was tested in six studies (n=1468), which had a pooled relative risk reduction of 15% compared with 19% in men and women combined. Data on men from two trials (n=211) were limited.w1 w2 Treatment duration did not modulate the effect of vitamin D significantly: fall reduction was 38% with a treatment duration of less than 12 months in three small trials (relative risk 0.62, 95% CI 0.42 to 0.91) compared with 17% with a treatment duration of 12 months or more in four larger trials (relative risk 0.83, 95% CI 0.72 to 0.96; P=0.07). The benefits of 700-1000 IU vitamin D a day on risk of falls were present in both ambulatory and institutionalised older individuals, as well as in trials with a mean age 65-79 years or higher.
 
Sensitivity analysis of supplemental vitamin D
In a sensitivity analysis, we examined the effect size for supplemental vitamin D when including studies meeting less stringent quality criteria. Seven studies were identified for the sensitivity analysis,w9-w15 six through our MeSH term search and one in the abstracts of the American Society for Bone and Mineral Research (table 4Go).w12 Three of these trials were excluded from the primary analysis for their insufficient assessment of falls,w9-w11 with incomplete fall assessment for the entire trial period in two studies.w9 w10 Three trials had an open study design and were not blinded,w12 w13 w14 and one trial enrolled patients in unstable health states.w15
 
The pooled effect of all 15 eligible trials including 17 786 individuals of any dose and any quality fall assessment suggested a non-significant 7% fall reduction with vitamin D (relative risk 0.93, 95% CI 0.87 to 1.01). However, variation among the 15 trials was larger than expected (Q test: P=0.009).
 
After adding the seven randomised controlled trials that did not meet our criteria for the primary analysis to the seven trials originally included the primary analysis, the pooled relative risk for the high dose of supplemental vitamin D (700-1000 IU vitamin D a day) was 0.92 (95% CI 0.85 to 0.99; total 17 281 individuals; table 5Go). However, variation among the 14 trials was larger than expected (Q-test: P=0.006), suggesting that adding the lower quality trials to the analysis introduces heterogeneity.
 
Trials of oral active forms of vitamin D
We found two randomised controlled trials of active forms of vitamin D that met our inclusion criteria (table 6).w16 w17 Falls were addressed as a primary outcome measure in both studies. No additional trials were identified for a sensitivity analysis. The two trials included 624 individuals with a mean age of 73 years, 70% of whom were women. In both studies, patients in the treatment group were more likely to experience hypercalcaemia (up to 3 mmol/l) than were those in the control group. The incidence of hypercalcaemia was twice as frequent in the treatment group as in the placebo group in one trial (12% v 6%),25 without details in the other.26 The pooled relative risk for fall prevention for active forms of vitamin D was 0.78 (95% CI 0.64 to 0.94), and active forms of vitamin D reduced the risk of falls by 22% (table 7).
 
Fall prevention with active forms of vitamin D compared with high dose supplemental vitamin D
 
The pooled relative risk for fall prevention of 0.78 for active forms of vitamin D was similar to the pooled relative risk of 0.81 for high dose of supplemental vitamin D. The ratio of the two effect sizes (pooled relative risk supplemental vitamin D/pooled relative risk active forms of vitamin D) was 1.04 (95% CI 0.84 to 1.31), suggesting that active forms and standard forms of vitamin D have statistically indistinguishable effects on fall prevention.
 
Test for publication bias
We found no evidence for publication bias in the eight supplemental vitamin D trials, according to both Begg's test and Egger's test.24 Although the Begg's test funnel plot indicated a potential absence of negative studies with small sample sizes, a trim and fill analysis did not confirm this possibility.27 28
 
Discussion
 
In this meta-analysis of eight double blind randomised controlled trials, the efficacy of supplemental vitamin D for fall prevention depended on dose and achieved 25(OH)D concentrations among individuals aged 65 years and older. No fall reduction was observed for a daily dose of less than 700 IU vitamin D or achieved serum 25(OH)D concentrations below 60 nmol/l. Daily vitamin D doses in the range of 700 IU to 1000 IU or achieved serum concentrations between 60 nmol/l and 95 nmol/l reduced the risk of falling by 19%. Given the absence of data beyond these beneficial ranges, our analyses don't preclude the possibility that higher doses of vitamin D or higher achieved 25(OH)D concentrations would have been even more efficient in reducing falls. At the high dose range of 700 IU to 1000 IU a day, the benefit of vitamin D was not significantly affected by type of supplemental vitamin D, gender, age, or level of independence. Notably, fall prevention with a high dose might not depend on additional calcium supplementation and was attained with treatment for less than 12 months (2-5 months). The benefit was sustained for 12-36 months.
 
An important risk factor for falls is muscle weakness, which is a prominent feature of the clinical syndrome of vitamin D deficiency and could plausibly mediate fracture risk through increasing susceptibility to falls.29 Binding of vitamin D to its nuclear receptor in muscle tissue may lead to de novo protein synthesis,29 30 a benefit that appears to precede the effect of vitamin D on bone.2
 
Comparison with other studies
Our findings confirm those in an earlier meta-analysis on falls from 2004,10 which showed that any vitamin D reduced falls in older individuals by 22%. Of three trials with supplemental vitamin D included in this earlier meta-analysis, one trial of 400 IU vitamin D a day showed a neutral effect,w8 whereas two trials with 800 IU a day suggested a beneficial effect on risk of falls (odds ratio 0.65, 95% CI 0.40 to 1.00).w6 w7 Since then, five double blind trials with sufficient quality fall assessment have been performed.w1 w2 w3 w4 w5 Our meta-analysis including these trials confirmed a benefit of 700 IU to 1000 IU vitamin D a day. Lending further support to our findings, several double blind randomised controlled trials have documented fracture prevention with 700-800 IU vitamin D a day,12 31 32 but not with 400 IU a day.33 34 35
 
We found a 38% reduction in the risk of falling for the high dose range of vitamin D with treatment for 2-5 months, and a sustained 17% fall reduction with treatment for 12-36 months. Indirect support for a rapid and sustained effect of vitamin D on falls comes from the large fracture trial by Chapuy and colleagues.36 Although falls were not assessed in this trial, supplementation most likely reduced the number of falls, leading to the reduction in fracture risk apparent after six months.
 
Fall reduction was assessed as one of the end points in a 2007 evidence report on vitamin D commissioned by the United States Department of Health and Human Services.37 The authors combined nine blinded and two open design trials (n=13 888) of any oral dose of vitamin D (D2 and D3) with or without calcium compared with calcium or placebo. Their pooled result suggested a non-significant 8% reduction in falls with vitamin D (odds ratio 0.92, 95% CI 0.85 to 1.00). Heterogeneity by dose was not detected. The result of the evidence report is consistent with our sensitivity analysis of all 15 eligible trials regardless of vitamin D dose and quality of fall assessment: we found a non-significant 7% fall reduction with vitamin D in 17 786 individuals. Variation among the 15 trials was larger than expected (Q test: P=0.009), however, even for the high dose sensitivity analysis (Q test: P=0.006).
 
A 2007 meta-analysis that focused on vitamin D3 found a 12% reduction in falls by pooling four trials irrespective of their vitamin D dose or quality of fall assessment.38 Our analysis of five trials with sufficient quality fall assessment showed that high doses of vitamin D3 reduced falls by 26%.
 
We addressed the additional importance of calcium in our primary analysis of high dose trials and documented a 23% fall reduction on the basis of results from six high quality trials of vitamin D alone compared with placebo or vitamin D plus calcium compared with calcium.w1 w3-w7 Vitamin D in combination with calcium compared with placebo reduced falls by 19% according to limited data from one trial.w2 Thus, the effect of 700-1000 IU vitamin D a day on falls may not depend on additional calcium supplementation, which could be explained by the calcium sparing effect of vitamin D.39 40
 
Active forms of vitamin D reduced falls by 22% and the high dose supplemental vitamin D reduced falls by 19%, suggesting no difference in efficacy between these alternatives in unselected older persons. However, the efficacy data for active forms of vitamin D was drawn from relatively few studies. In addition, active forms cost more and have a higher risk profile, so we believe adequate dosing of supplemental vitamin D should be preferred. Importantly, the efficacy of active forms of vitamin D adds to the evidence that improved vitamin D status reduces the risk of falling in older individuals.
 
Limitations of study
As with all meta-analyses, this review has the potential for publication bias. However, we found no evidence for publication bias using the Begg's test and the Egger's test with all eight trials.24 Although the Begg's test funnel plot suggested a possible absence of negative studies with small sample sizes, the trim and fill analysis did not confirm this suggestion.27 28 With respect to trial quality, our primary analysis was restricted to trials with a double blind design and sufficient quality fall assessment to address the efficacy of vitamin D for fall prevention. In our sensitivity analysis that included additional trials with an open study design or insufficient fall assessment, study variation was larger than expected for the pooled result from all 15 trials. Even within the 14 high dose trials, variation between trials was larger than expected, supporting our pre-defined strategy of focusing on fall efficacy from double blind trials with sufficient fall assessment.
 
Implications for future research
We found a greater fall reduction in studies with a maximum vitamin D daily dose of 1000 IU a day than in studies with lower doses; therefore, higher doses may be even more effective. Such doses should be explored in future research to optimise the fall prevention benefit with vitamin D.
 
Conclusions
Doses of 700 IU to 1000 IU supplemental vitamin D a day could reduce falls by 19% or by up to 26% with vitamin D3. This benefit may not depend on additional calcium supplementation, was significant within 2-5 months of treatment, and extended beyond 12 months of treatment. Conversely, our results do not support the clinical use of vitamin D doses below 700 IU a day for the prevention of falls among older individuals. A 25(OH)D concentration of at least 60 nmol/l is required for fall prevention; therefore, a daily intake of at least 700 IU supplemental vitamin D is warranted in all individuals age 65 and older. Notably, good adherence is essential as the effect of vitamin D on falls will not be proportional below 700 IU a day. Furthermore, it is possible that greater benefits may be achieved with the use of vitamin D3 instead of vitamin D2. Finally, active forms of vitamin D do not appear to be more effective than 700-1000 IU of supplemental vitamin D for fall prevention in older persons.
 
 
 
 
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