Suzanne C. van Dijk

Rationale and design of the B-PROOF study, a randomized controlled trial on the effect of supplemental intake of vitamin B12 and folic acid on fracture incidence

BackgroundOsteoporosis is a major health problem, and the economic burden is expected to rise due to an increase in life expectancy throughout the world. Current observational evidence suggests that an elevated homocysteine concentration and poor vitamin B12 and folate status are associated with an increased fracture risk. As vitamin B12 and folate intake and status play a large role in homocysteine metabolism, it is hypothesized that supplementation with these B-vitamins will reduce fracture incidence in elderly people with an elevated homocysteine concentration.Methods/DesignThe B-PROOF (B-Vitamins for the PRevention Of Osteoporotic Fractures) study is a randomized double-blind placebo-controlled trial. The intervention comprises a period of two years, and includes 2919 subjects, aged 65 years and older, independently living or institutionalized, with an elevated homocysteine concentration (≥ 12 μmol/L). One group receives daily a tablet with 500 μg vitamin B12 and 400 μg folic acid and the other group receives a placebo tablet. In both tablets 15 μg (600 IU) vitamin D is included. The primary outcome of the study is osteoporotic fractures. Measurements are performed at baseline and after two years and cover bone health i.e. bone mineral density and bone turnover markers, physical performance and physical activity including falls, nutritional intake and status, cognitive function, depression, genetics and quality of life. This large multi-center project is carried out by a consortium from the Erasmus MC (Rotterdam, the Netherlands), VUmc (Amsterdam, the Netherlands) and Wageningen University, (Wageningen, the Netherlands), the latter acting as coordinator.DiscussionTo our best knowledge, the B-PROOF study is the first intervention study in which the effect of vitamin B12 and folic acid supplementation on osteoporotic fractures is studied in a general elderly population. We expect the first longitudinal results of the B-PROOF intervention in the second semester of 2013. The results of this intervention will provide evidence on the efficacy of vitamin B12 and folate supplementation in the prevention of osteoporotic fractures.Trial RegistrationThe B-PROOF study is registered with the Netherlands Trial (NTR NTR1333) and with ClinicalTrials.gov (NCT00696514).

Effect of daily vitamin B-12 and folic acid supplementation on fracture incidence in elderly individuals with an elevated plasma homocysteine concentration: B-PROOF, a randomized controlled trial

BACKGROUND Elevated plasma homocysteine concentrations are a risk factor for osteoporotic fractures. Lowering homocysteine with combined vitamin B-12 and folic acid supplementation may reduce fracture risk. OBJECTIVE This study [B-vitamins for the PRevention Of Osteoporotic Fractures (B-PROOF)] aimed to determine whether vitamin B-12 and folic acid supplementation reduces osteoporotic fracture incidence in hyperhomocysteinemic elderly individuals. DESIGN This was a double-blind, randomized, placebo-controlled trial in 2919 participants aged ≥65 y with elevated homocysteine concentrations (12-50 μmol/L). Participants were assigned to receive daily 500 μg vitamin B-12 plus 400 μg folic acid or placebo supplementation for 2 y. Both intervention and placebo tablets also contained 600 IU vitamin D3. The primary endpoint was time to first osteoporotic fracture. Exploratory prespecified subgroup analyses were performed in men and women and in individuals younger than and older than age 80 y. Data were analyzed according to intention-to-treat and per-protocol principles. RESULTS Osteoporotic fractures occurred in 61 persons (4.2%) in the intervention group and 75 persons (5.1%) in the placebo group. Osteoporotic fracture risk was not significantly different between groups in the intention-to-treat analyses (HR: 0.84; 95% CI: 0.58, 1.21) or per-protocol analyses (HR: 0.81; 95% CI: 0.54, 1.21). For persons aged >80 y, in per-protocol analyses, osteoporotic fracture risk was lower in the intervention group than in the placebo group (HR: 0.27; 95% CI: 0.10, 0.74). The total number of adverse events (including mortality) did not differ between groups. However, 63 and 42 participants in the intervention and placebo groups, respectively, reported incident cancer (HR: 1.56; 95% CI: 1.04, 2.31). CONCLUSIONS These data show that combined vitamin B-12 and folic acid supplementation had no effect on osteoporotic fracture incidence in this elderly population. Exploratory subgroup analyses suggest a beneficial effect on osteoporotic fracture prevention in compliant persons aged >80 y. However, treatment was also associated with increased incidence of cancer, although the study was not designed for assessing cancer outcomes. Therefore, vitamin B-12 plus folic acid supplementation cannot be recommended at present for fracture prevention in elderly people. The B-PROOF study was registered with the Netherlands Trial Register (trialregister.nl) as NTR1333 and at clinicaltrials.gov as NCT00696414.

Non-linear associations between serum 25-OH vitamin D and indices of arterial stiffness and arteriosclerosis in an older population

BACKGROUND several studies have been pointing towards a non-linear relationship between serum 25(OH)D and cardiovascular disease. Next to vitamin D deficiency, also higher levels of 25(OH)D have been reported to be associated with increased cardiovascular risk. We aimed to investigate the nature of the relationship between serum 25(OH)D and measures of arterial stiffness and arteriosclerosis in an elderly population. DESIGN cross-sectional. SETTING/SUBJECTS a subgroup of the B-PROOF study was included to determine associations between serum 25(OH)D and arterial stiffness and atherosclerosis (n = 567, 57% male, age 72.6 ± 5.6 years, mean serum 25(OH)D 54.6 ± 24.1 nmol/l). METHODS carotid intima media thickness (IMT) was assessed using ultrasonography and pulse wave velocity (PWV) was determined with applanation tonometry. Associations were tested using multivariable restricted cubic spline functions and stratified linear regression analysis. RESULTS the associations between serum 25(OH)D and carotid IMT or PWV were non-linear. Spline functions demonstrated a difference between 25(OH)D deficient and sufficient individuals. In serum 25(OH)D sufficient participants (≥50 nmol/l; n = 287), a positive association with IMT and serum 25(OH)D was present (β 1.24; 95%CI [0.002; 2.473]). PWV levels were slightly lower in vitamin D deficient individuals, but the association with 25(OH)D was not significant. CONCLUSION our study demonstrates that associations of serum 25(OH)D and PWV and IMT in an elderly population are not linear. In particular from serum 25(OH)D levels of 50 nmol/l and up, there is a slight increase of IMT with increasing 25(OH)D levels.

Homocysteine level is associated with aortic stiffness in elderly: Cross-sectional results from the B-PROOF study

Objective: Homocysteine has been shown to be a more accurate predictor of cardiovascular mortality in very old persons than models based on classical risk factors. Arterial stiffening is a structural abnormality involved in the pathway of cardiovascular disease. We expect this underlying pathophysiology to be a possible explanation for the association between homocysteine and cardiovascular risk, particularly in older populations. Methods: Baseline cross-sectional data of the B-PROOF study were used to determine associations between homocysteine and outcomes of vascular function and structure. The cardiovascular subgroup of the B-PROOF study was included [n = 560, 58% men, age 72.6 ± 5.5 years, median homocysteine level 14.2 &mgr;mol/l (IQR 13.0–16.6)]. We assessed carotid distensibility coefficient, carotid compliance coefficient, aortic pulse wave velocity (aPWV), augmentation index (AIx) and aortic pulse pressure (aortic PP). Associations were tested using linear regression analysis and ANCOVA and were adjusted for possible confounders including age, sex, renal function, mean arterial pressure and heart rate. Results: Ln-homocysteine was strongly associated with aPWV [&bgr; 0.005 95% confidence interval (0.001–0.009)]. Furthermore, this association was shown to be age-dependent (P = 0.02) and it was most strong in the upper tertile of age (77–98 years). No significant associations with ln-homocysteine were observed for AIx, carotid distensibility coefficient and compliance coefficient and aortic PP. Sex stratification shows the association between ln-homocysteine and aPWV is only significant in men. Conclusion: In older persons, homocysteine is associated with aortic stiffness, predominantly in the oldest old. This suggests that the strong association between homocysteine and cardiovascular mortality in the elderly may be mediated by aortic stiffness.

Relative importance of summer sun exposure, vitamin D intake, and genes to vitamin D status in Dutch older adults: The B-PROOF study.

BACKGROUND/OBJECTIVES The prevalence of vitamin D deficiency among seniors is high. Whereas sun exposure, vitamin D intake, genes, demographics, and lifestyle have been identified as being important determinants of vitamin D status, the impact of these factors is expected to differ across populations. To improve current prevention and treatment strategies, this study aimed to explore the main determinants of vitamin D status and its relative importance in a population of community-dwelling Dutch older adults. METHODS/SUBJECTS Serum 25-hydroxyvitamin D (25(OH)D) was measured in 2857 adults aged ≥65 years. Sun exposure was assessed with a structured questionnaire (n=1012), vitamin D intake using a Food Frequency Questionnaire (n=596), and data on genetic variation that may affect 25(OH)D status was obtained for 4 genes, DHCR7 (rs12785878), CYP2R1 (rs10741657), GC (rs2282679), and CYP24A1 (rs6013897) (n=2530). RESULTS Serum 25(OH)D concentrations <50nmol/L were observed in 45% of the population; only 6% of these participants used vitamin D supplements. Sun exposure (being outside daily during summer: 66±25nmol/L vs not being outside daily during summer: 58±27nmol/L, P=0.02) and vitamin D intake (per unit μg/day during winter/spring: 3.1±0.75nmol/L, P<0.0001) were associated with higher 25(OH)D concentrations. Major allele carriers of SNPs related to DHCR7, CYP24A1, and GC, as well as CYP2R1 minor allele carriers had the highest 25(OH)D concentrations. Together, sun (R2=0.29), vitamin D intake (R2=0.24), and genes (R2=0.28) explained 35% (R2=0.35) of the variation in 25(OH)D concentrations during summer/autumn period, when adjusted for age, sex, BMI, education, alcohol consumption, smoking, physical activity, and self-rated health status (n=185). CONCLUSION The investigated determinants explained 35% of 25(OH)D status. Of the three main determinants under study, sun exposure still appeared to be an important determinant of serum 25(OH)D in older individuals, closely followed by genes, and vitamin D intake. Given the low frequency of vitamin D supplement use in this population, promoting supplement use may be an inexpensive, easy, and effective strategy to fight vitamin D deficiency.

Effect of vitamin B12 and folic acid supplementation on biomarkers of endothelial function and inflammation among elderly individuals with hyperhomocysteinemia.

B-vitamin trials failed to demonstrate beneficial effects on cardiovascular outcomes, but hyperhomocysteinemia still stands out as an independent cardiovascular risk factor, particularly in elderly individuals. B-vitamins may influence early vascular dysfunction, such as endothelial dysfunction, or may have adverse effects, for example on inflammation. We investigated the effect of B-vitamins on endothelial function and inflammation within an interventional study. This study was conducted within the framework of the B-PROOF trial, which included 2919 hyperhomocysteinemic elderly individuals, who received daily vitamin B12 (500 μg) and folic acid (400 μg) or placebo for 2 years. Using an electrochemiluminescence platform, we measured intercellular adhesion molecule 1 (ICAM-1), vascular adhesion molecule 1 (VCAM-1), serum amyloid A (SAA), vascular endothelial growth factor (VEGF) and C-reactive protein (CRP) at baseline and follow-up in a subsample of 522 participants (271 intervention group; 251 placebo). Treatment effects were analyzed with ANCOVA. The participants had a mean age of 72 years, and 55% of them were male. At the 2-year follow-up, B-vitamins did not change the ICAM-1 (+36% change in the intervention group versus +32% change in the placebo group; p = 0.72), VCAM-1 (+27% vs +25%; p = 0.39), VEGF (–1% vs +4%; p = 0.40), SAA (+34% vs +38%; p = 0.85) or CRP levels (+26% vs +36%; p = 0.70) as compared to placebo. In conclusion, in elderly patients with hyperhomocysteinemia, vitamin B12 and folic acid are unlikely to influence either endothelial function or low-grade systemic inflammation. ClinicalTrials.gov Identifier: NCT00696514

Oscillometry and applanation tonometry measurements in older individuals with elevated levels of arterial stiffness

ObjectiveIndices of arterial stiffness and aortic pressure are usually assessed by applanation tonometry. The more recently introduced oscillometric device is simpler to use. Several studies have investigated the agreement between these two devices, but not in populations with elevated levels of arterial stiffness. Therefore, we evaluated the agreement in an elderly population with high risk of arterial stiffness. Patients and methodsWe included a subgroup of the B-PROOF study (n=344, mean age 73 years, 60% men), whose aortic pulse wave velocity (aPWV), aortic augmentation index (AIx), aortic pulse pressure (PP), and aortic systolic blood pressure (SBP) were assessed both with applanation tonometry (SphygmoCor) and with oscillometry (Arteriograph). We investigated agreement between the two devices using Pearson correlations and Bland–Altman analysis. We carried out a stratified analysis in participants with more pronounced arterial stiffness (SphygmoCor aPWV>12 m/s). ResultsThe oscillometric method produced higher values of AIx, aortic PP, and aortic SBP (P<0.01) than applanation tonometry. aPWV values were lower (P<0.01) and were not correlated (r=−0.06, P=0.92), whereas AIx measurements (r=0.35 P<0.01), aortic PP (r=0.57 P<0.01), and aortic SBP (r=0.68 P<0.01) measurements were correlated. Bland–Altman analysis showed insufficient agreement between the two devices, especially in those with elevated levels of arterial stiffness (aPWV>12 m/s). ConclusionParticularly in the elderly with elevated levels of arterial stiffness, measurements of aPWV obtained with oscillometry and applanation tonometry show poor agreement. Also, AIx, aortic SBP, and aortic PP show clearly less than optimal agreement.

Central but not peripheral fat mass percentage is associated with blood pressure components in the elderly

BACKGROUND the human body composition changes with advances in age. Particularly, the central fat amount increases. Because the central fat mass is a cardiovascular risk factor, we investigated whether in an elderly population, fat mass (measured at different bodily locations) is associated with peripheral and central blood pressure components. METHODS cross-sectional design. Using dual-energy X-ray absorptiometry (DEXA), fat mass was measured within a geriatric outpatient clinic population. Blood pressure was measured with an oscillometric device, and aortic blood pressure and augmentation index (AIx) were obtained by radial artery tonometry, using the SphygmoCor system. Multivariate adjustment for confounders was performed using linear regression analyses. RESULTS totally, 216 subjects were included (age 77.3 years ± 6.1, 34.7% male). The truncal fat mass percentage, but not the peripheral fat mass percentage, was positively associated with the peripheral systolic blood pressure (SBP) [beta 0.07 (95% CI: 0.02 to 0.11)] and the peripheral pulse pressure (PP) [beta 0.07 (95% CI: 0.02 to 0.11)], but negatively with the peripheral diastolic blood pressure (DBP) [beta -0.16 (95% CI -0.27 to -0.04)]. The truncal fat mass percentage was similarly associated with estimated aortic blood pressure components, but no association was found between the truncal fat mass percentage and the AIx. CONCLUSION in older persons, the truncal fat mass percentage as a reflection of the central fat mass percentage, but not the peripheral fat mass percentage is associated with peripheral and aortic blood pressure components.

Folate and vitamin B12-related biomarkers in relation to brain volumes

Aim: We investigated cross-sectional associations between circulating homocysteine, folate, biomarkers of vitamin B12 status and brain volumes. We furthermore compared brain volumes of participants who received daily folic acid and vitamin B12 supplementation with participants who did not. Methods: Participants of the B-PROOF study (n = 2919) were assigned to 400 µg folic acid and 500 µg vitamin B12, or a placebo. After two years of intervention, T1-weighted magnetic resonance imaging (MRI) scans were made in a random subsample (n = 218) to obtain grey and white matter volume, and total brain volume (TBV). Plasma homocysteine, serum folate, vitamin B12, holotranscobalamin, and methylmalonic acid concentrations were measured. Results: Multiple linear regression analyses showed inverse associations between plasma homocysteine with TBV (β = −0.91, 95% CI −1.85–0.03; p = 0.06) and between serum folate and TBV (β = −0.20, 95% CI −0.38, −0.02; p = 0.03). No significant associations were observed for serum vitamin B12 and holotranscobalamin. Fully adjusted ANCOVA models showed that the group that received B-vitamins had a lower TBV (adjusted mean 1064, 95% CI 1058–1069 mL) than the non-supplemented group (1072, 95% CI 1067–1078 mL, p = 0.03). Conclusions: Results were contradictory, with higher Hcy levels associated with lower TBV, but also with higher folate levels associated with lower TBV. In addition, the lack of a baseline measurement withholds us from giving recommendations on whether folic acid and vitamin B12 supplementation will be beneficial above and beyond normal dietary intake for brain health.