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. 2018 Dec 17;2018(12):CD011906. doi: 10.1002/14651858.CD011906.pub2

Van der Zwaluw 2014.

Methods Multicentre, double‐blind, randomised, placebo‐controlled trial, with 2‐year duration of treatment and 2‐year duration of follow‐up
Participants Location: 3 research centres in the Netherlands: VU University Medical Center (Amsterdam), Erasmus Medical Center (Rotterdam), and Wageningen University (WU, Wageningen)
Recruitment: Dutch elderly men and women who participated in the B‐PROOF (B‐Vitamins for the Prevention of Osteoporotic Fractures) study which assessed the efficacy of oral supplementation with 400 µg folic acid and 500 µg vitamin B in the prevention of fractures, with cognitive performance as secondary outcome.
Most participants were recruited via registries of municipalities in surroundings of the research centres.
The study was conducted between October 2008 and March 2013.
Number randomised: 1516 in intervention, 1511 in comparison
Participant (baseline) characteristics:

  • Age (mean, SD):

    • total population (n=2919): 74.1 years (6.5)

    • cognitive sub‐sample (n=856):

      • B vitamin (n=425): 72.6 years (5.7)

      • placebo (n=431): 72.6 years (5.8)

  • Gender (males, n %):

    • total population (n=2919): 1459 (50)

    • cognitive sub‐sample (n=856):

      • B vitamin (n=425): 244 (57)

      • placebo (n=431): 255 (59)

  • Main diagnosis: not reported


Inclusion criteria: age 65 years or older, having an elevated plasma homocysteine level (12–50 µmol/L), being competent to make own decisions, and having a compliant tablet intake (≥ 85%) in the run‐in period
Exclusion criteria: cancer diagnosis within the last 5 years except for basal cell carcinoma and squamous cell carcinoma, bedridden, serum creatinine level > 150 µmol/L, current or recent (< 4 months) use of intramuscular injections of vitamin B12 or folic acid supplementations (> 300 µmol), and participation in other intervention studies
6% of the study population had a MMSE < 25.
Interventions Intervention (n=1516):
B vitamin group: 400 µg folic acid and 500 µg vitamin B12 daily
Comparator group (n=1511): placebo.
Treatment was continued for 2 years.
Use of additional interventions (common to both treatment arms): Both tablets contained 15 µg (600 IU) vitamin D3.
Outcomes Outcomes of interest in review:
Quote: "The primary goal of the B‐PROOF study was [to] assess the efficacy of oral supplementation with folic acid and vitamin B12 in the prevention of fractures, with cognitive performance as a secondary outcome."
The 'primary' outcome of the cognitive study was "the difference between treatment groups in performance on episodic memory after 2 years of supplementation."
'Secondary' cognitive outcomes were "differences in performance at follow‐up on attention and working memory, information processing speed, executive function, and single test scores."
Quote: "Cognitive performance was assessed at baseline and at the end of the intervention period by well‐trained research assistants following a standard protocol. We used the MiniMental State Examination (MMSE) and an extensive, sensitive, and validated neuropsychological test battery" ..that "consisted of the Rey Auditory Verbal Learning Test (RAVLT), Digit Span forward and backward, Trail Making Test (TMT) parts A and B, Stroop Color‐Word Test, Symbol Digit Modalities Test, and Letter Fluency (3 letters)".
Quote: "To compare results of the individual cognitive tests and to limit the number of dependent variables, crude test scores were clustered into compound scores for the 4 neuropsychological domains".
"For all 4 cognitive domains, predefined interaction terms of treatment with sex, baseline age (< 80, ≥ 80 years), plasma HCY (< 14.4, ≥ 14.4 µmol/L), and APOE genotype (APOE e4 or not) were tested".
Cognitive outcomes:

  • global cognitive function measured with MMSE at 2 years, with higher values indicating benefit

  • executive functioning measured with Trial making test (part B/partA) at 2 years, with lower values indicating benefit

  • executive functioning measured with Stroop Interference (part 3 ‐ (part 1 + part 2/2/)) at 2 years, with lower values indicating benefit

  • working memory measured with Digit span backward at 2 years, with higher values indicating benefit

  • working memory measured with Digit span forward at 2 years, with higher values indicating benefit

  • episodic memory measured with RAVLT‐Decay (delayed recall trial 5) at 2 years, with higher values indicating benefit

  • episodic memory measured with RAVLT‐ trials I‐V, immediate Recall max 75 words at 2 years, with higher values indicating benefit

  • episodic memory measured with RAVLT‐ trial 9 Recognition max 30 words at 2 years, with higher values indicating benefit

  • speed of processing measured with Trail making part A at 2 years, with lower values indicating benefit

  • speed of processing measured with Stroop 1 and 2 mean at 2 years, with lower values indicating benefit

  • speed of processing measured with Symbol digit modalities test at 2 years, with higher values indicating benefit

  • verbal fluency measured with Verbal Fluency ‐ total no at 2 years, with higher values indicating benefit
Notes Funding sources, quote: “B‐PROOF was supported and funded by The Netherlands Organization for Health Research and Development (ZonMw, grant 6130.0031), the Hague; unrestricted grant from NZO (Dutch Dairy Association), Zoetermeer; MCO Health, Almere; NCHA (Netherlands Consortium Healthy Ageing) Leiden/Rotterdam; Ministry of Economic Affairs, Agriculture and Innovation (project KB‐15‐004‐003), the Hague; Wageningen University, Wageningen; VU University Medical Center, Amsterdam; and Erasmus Medical Center, Rotterdam. All organizations are based in the Netherlands. The sponsors had no role in the design or implementation of the study, data collection, data management, data analysis, data interpretation, or in the preparation, review, or approval of the manuscript."
Declarations of interest, quote: “The authors report no disclosures relevant to the manuscript."
Treatment adherence
"Average compliance to treatment was 90%, and 84% of all participants had an overall compliance ≥ 80%. Compliance was equal for both treatment groups".
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk Quote: “Randomization was done by an independent person by means of computer‐generated randomization numbers in stratified permuted blocks of size 4, stratified by study center, sex, age (65–79 years, ≥ 80 years), and HCY levels (12–17 mmol, ≥ 18 mmol)".
Comment: computer‐generated sequence
Allocation concealment (selection bias) Low risk Quote: “Randomization was done by an independent person".
Comment: allocation probably concealed
Blinding of participants and personnel (performance bias) 
 All outcomes Low risk Quote: “Participants and employees of the study were blinded until data analyses were finished."
Comment: participants and personnel blinded
Blinding of outcome assessment (detection bias) 
 All outcomes Low risk Quote: “Participants and employees of the study were blinded until data analyses were finished."
Comment: outcome assessors blinded
Incomplete outcome data (attrition bias) 
 All outcomes High risk Quote: from CONSORT flow diagram, 22‐24% attrition from each group
Comment: significant loss of participants, but reasons given and appeared balanced between groups
Selective reporting (reporting bias) Low risk Comment: No differences identified in the outcomes reported in the protocol (clinicaltrials.gov: NCT00696514) and the article. All outcomes specified in the Methods were reported in the Results.
Other bias Low risk Comment: no other apparent sources of bias