EAL

NSUP: Vitamin D (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To review and synthesize the literature regarding the effect of vitamin D and falls.

Inclusion Criteria:

RCTs with a parallel design and factorial design studies examining the relationship between vitamin D and falls.

Exclusion Criteria:

Research regarding vitamin D and falls that was not either RCT with parallel design or factorial design
Research not involving vitamin D and falls.

Description of Study Protocol:

Recruitment

The following databases were searched:

MEDLINE (1996 to the third week of June 2006)
Embase (2002 to the 25th week of 2006)
CINAHL (1982 to the fourth week of June 2006)
AMED (1985 to June 2006)
Biological Abstracts (1990 to February 2005)
The Cochrane Central Register of Controlled Trials (CENTRAL; second quarter of 2006).

No language restrictions were applied and studies were restricted to human subjects.

Design

Studies for inclusion were limited, whenever possible, to randomized, controlled trial (RCTs) to limit bias. Prospective cohorts, case-control and before-after studies were included due to the lack of studies addressing the association between serum 25(OH)D concentrations and bone health outcomes.

The results of the search were assessed using a three-step process:

First, bibliographic records, including title, keywords and abstract, were screened by one reviewer
Potentially relevant records were then screened independently by two reviewers using the full text report and strict eligibility criteria
Conflicts were discussed and resolved through consensus or adjudication by a third reviewer.
Relevant studies were subsequently assessed for study design and categorized by question.

Statistical Analysis

Meta-analysis of RCTs that assessed interventions, populations and outcomes (e.g., fractures or falls) was concluded using a random effects model, with an assessment of statistical heterogeneity
For continuous outcomes (e.g., serum 25(OH)D concentrations and Bone Mineral Density (BMD), the difference in means between treatment groups was used for the meta-analyses: The absolute change in 25(OH)D concentrations was used for quantitative pooling. A weighted average was used to calculate the 25(OH)D values for the combined treatment and placebo group. The difference in means was then calculated using the weighted averages for the two combined groups.
To avoid differences in the reporting of units for 25(OH)D concentrations, (i.e., nmol per L, ng per ml), all values were converted to nmol per L that was the unit used for data synthesis.

Data Collection Summary:

Timing of Measurements

The results of the search were assessed using a three-step process:

First, bibliographic records, including title, keywords and abstract, were screened by one reviewer
Potentially relevant records were then screened independently by two reviewers using the full-text report and strict eligibility criteria
Conflicts were discussed and resolved through consensus or adjudication by a third reviewer
Relevant studies were subsequently assessed for study design and categorized by question.

Dependent Variables

Incident falls.

Independent Variables

Vitamin D status.

Control Variables

Community vs. institutionalized residents
Age
Gender.

Description of Actual Data Sample:

Initial N

14 total trials in 16 published reports

12 were RCTs with a parallel design
Four used a factorial design.

Other

5,445 participants received the intervention within the 12 RCTs
5,212 received the control or placebo
In the cluster randomized trials, 6,719 participants received the intervention and 6,603 received the control.

Age

Six trials included post-menopausal women only
Remaining eight trials included a combination of post-menopausal women and elderly men.

Summary of Results:

Findings

There is inconsistent evidence that supplemental vitamin D reduces falls in post-menopausal women and older men
The results from trials examining the effect of supplemental vitamin D on falls is consistent with 12 of the 14 trials demonstrating a non-significant reduction in falls
However, when combining RCTs there is inconsistent evidence regarding the effect of supplemental vitamin D on falls
The combination of 12 trials of either oral or injectable vitamin D₂vitamin D₃ supplementation with calcium showed a reduction in fall risk, whereas four RCTs or oral vitamin D₃ did not
Sub-group analyses showed a significant reduction in falls upon combining trials of post-menopausal women only
Sensitivity analyses showed a significant reduction in falls when combining:
1. RCTs that explicitly defined falls and the method of fall ascertainment
2. Those in which the allocation concealment was unclear.

Author Conclusion:

There is inconsistent evidence that supplemental vitamin D reduces falls in post-menopausal women and older men.

Funding Source:

Government:

NIH

Reviewer Comments:

An evaluation of publication bias suggested the possibility of bias given a lack of smaller trials that failed to find an effect of vitamin D on fracture reduction.

Quality Criteria Checklist: Review Articles
Relevance Questions
	1.	Will the answer if true, have a direct bearing on the health of patients?	Yes
	2.	Is the outcome or topic something that patients/clients/population groups would care about?	Yes
	3.	Is the problem addressed in the review one that is relevant to dietetics practice?	Yes
	4.	Will the information, if true, require a change in practice?	Yes

Validity Questions
	1.	Was the question for the review clearly focused and appropriate?	Yes
	2.	Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described?	Yes
	3.	Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased?	Yes
	4.	Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible?	Yes
	5.	Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined?	Yes
	6.	Was the outcome of interest clearly indicated? Were other potential harms and benefits considered?	Yes
	7.	Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described?	Yes
	8.	Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included?	Yes
	9.	Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed?	Yes
	10.	Was bias due to the review's funding or sponsorship unlikely?	Yes