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Predictors of 25-Hydroxyvitamin D Concentration Measured at Multiple Time Points in a Multiethnic Population.

ABSTRACT: The evidence for a relationship between serum vitamin D levels and nonskeletal health outcomes is inconsistent. The validity of single or predicted measurements of 25-hydroxyvitamin D (25(OH)D) concentration is unknown, as levels of this biomarker are highly seasonally variable. We compared models of 25(OH)D measured at baseline, at multiple time points throughout the year, and averaged over the year among 309 persons in Toronto, Ontario, Canada (43°N latitude) during 2009-2013. Information and blood samples were collected every 2 months. Baseline and average 25(OH)D concentrations were correlated (r = 0.88). Major factors associated with 25(OH)D level were similar across models and included race/ethnicity (concentrations in non-European groups were lower than those in Europeans), vitamin D supplement use of ?1,000 IU/day (18.9 nmol/L (95% confidence interval (CI): 16.1, 21.8) vs. no supplement use in a full data set with all factors), and the presence of the group-specific component/vitamin D binding protein gene (GC/DBP) rs4588 functional polymorphism (AA vs. CC: -16.7 nmol/L (95% CI: -26.2, -7.1); CA vs. CC: -10.7 nmol/L (95% CI: -14.9, -6.5)). Most factors had similar associations in Europeans and non-Europeans. Genetic factors may play a greater role in average 25(OH)D concentrations. Prediction models for 25(OH)D are challenging and population-specific, but use of genetic factors along with a few common population-relevant, quantifiable nongenetic factors with strong associations may be the most feasible approach to vitamin D assessment over time.

SUBMITTER: Knight JA

PROVIDER: S-EPMC5859989 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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Predictors of 25-Hydroxyvitamin D Concentration Measured at Multiple Time Points in a Multiethnic Population.

Knight Julia A JA Wong Jody J Cole David E C DEC Lee Tim K TK Parra Esteban J EJ

American journal of epidemiology 20171101 10

The evidence for a relationship between serum vitamin D levels and nonskeletal health outcomes is inconsistent. The validity of single or predicted measurements of 25-hydroxyvitamin D (25(OH)D) concentration is unknown, as levels of this biomarker are highly seasonally variable. We compared models of 25(OH)D measured at baseline, at multiple time points throughout the year, and averaged over the year among 309 persons in Toronto, Ontario, Canada (43°N latitude) during 2009-2013. Information and ...[more]

PMID: 28549072

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Project description:BackgroundLow serum 25-hydroxyvitamin D [25(OH)D] concentrations in patients with colorectal cancer have been consistently associated with higher mortality in observational studies. It is unclear whether low 25(OH)D levels directly influence colorectal cancer mortality. To minimize bias, we use genetic variants associated with vitamin D levels to evaluate the association with overall and colorectal cancer-specific survival.MethodsSix genetic variants have been robustly identified to be associated with 25(OH)D levels in genome-wide association studies. On the basis of data from the International Survival Analysis in Colorectal Cancer Consortium, the individual genetic variants and a weighted genetic risk score were tested for association with overall and colorectal cancer-specific survival using Cox proportional hazards models in 7,657 patients with stage I to IV colorectal cancer, of whom 2,438 died from any cause and 1,648 died from colorectal cancer.ResultsThe 25(OH)D decreasing allele of SNP rs2282679 (GC gene, encodes group-specific component/vitamin D-binding protein) was associated with poorer colorectal cancer-specific survival, although not significant after multiple-testing correction. None of the other five SNPs showed an association. The genetic risk score showed nonsignificant associations with increased overall [HR = 1.54; confidence interval (CI), 0.86-2.78] and colorectal cancer-specific mortality (HR = 1.76; 95% CI, 0.86-3.58). A significant increased risk of overall mortality was observed in women (HR = 3.26; 95% CI, 1.45-7.33; P heterogeneity = 0.01) and normal-weight individuals (HR = 4.14; 95% CI, 1.50-11.43, P heterogeneity = 0.02).ConclusionsOur results provided little evidence for an association of genetic predisposition of lower vitamin D levels with increased overall or colorectal cancer-specific survival, although power might have been an issue.ImpactFurther studies are warranted to investigate the association in specific subgroups.

Dataset Information

Predictors of 25-Hydroxyvitamin D Concentration Measured at Multiple Time Points in a Multiethnic Population.

Publications

Predictors of 25-Hydroxyvitamin D Concentration Measured at Multiple Time Points in a Multiethnic Population.

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