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- Jiang, X, et al.
(författare)
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Circulating vitamin D concentrations and risk of breast and prostate cancer: a Mendelian randomization study
- 2019
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Ingår i: International journal of epidemiology. - : Oxford University Press (OUP). - 1464-3685 .- 0300-5771. ; 48:5, s. 1416-1424
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundObservational studies have suggested an association between circulating vitamin D concentrations [25(OH)D] and risk of breast and prostate cancer, which was not supported by a recent Mendelian randomization (MR) analysis comprising 15 748 breast and 22 898 prostate-cancer cases. Demonstrating causality has proven challenging and one common limitation of MR studies is insufficient power.MethodsWe aimed to determine whether circulating concentrations of vitamin D are causally associated with the risk of breast and prostate cancer, by using summary-level data from the largest ever genome-wide association studies conducted on vitamin D (N = 73 699), breast cancer (Ncase = 122 977) and prostate cancer (Ncase = 79 148). We constructed a stronger instrument using six common genetic variants (compared with the previous four variants) and applied several two-sample MR methods.ResultsWe found no evidence to support a causal association between 25(OH)D and risk of breast cancer [OR per 25 nmol/L increase, 1.02 (95% confidence interval: 0.97–1.08), P = 0.47], oestrogen receptor (ER)+ [1.00 (0.94–1.07), P = 0.99] or ER− [1.02 (0.90–1.16), P = 0.75] subsets, prostate cancer [1.00 (0.93–1.07), P = 0.99] or the advanced subtype [1.02 (0.90–1.16), P = 0.72] using the inverse-variance-weighted method. Sensitivity analyses did not reveal any sign of directional pleiotropy.ConclusionsDespite its almost five-fold augmented sample size and substantially improved statistical power, our MR analysis does not support a causal effect of circulating 25(OH)D concentrations on breast- or prostate-cancer risk. However, we can still not exclude a modest or non-linear effect of vitamin D. Future studies may be designed to understand the effect of vitamin D in subpopulations with a profound deficiency.
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- Longnecker, MP, et al.
(författare)
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The reproducibility and validity of a self-administered semiquantitative food frequency questionnaire in subjects from South Dakota and Wyoming
- 1993
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Ingår i: Epidemiology. ; 4, s. 356-365
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Tidskriftsartikel (refereegranskat)abstract
- Department of Epidemiology, UCLA School of Public Health 90024-1772. Most validation studies of food frequency questionnaires have been done in populations capable of reporting their diet with unusual accuracy. In this study of ranchers and subjects selected at random, we compared nutrient intakes as assessed with multiple diet records with those assessed with a self-administered food frequency questionnaire (the Harvard-Willett instrument with 116 food items). One hundred thirty-eight subjects from South Dakota and Wyoming, 64 males and 74 females, completed at least one food frequency questionnaire and multiple 1-day diet records (mean = 5 days) during a 6-month to 1-year period. Of invited subjects, 88% participated; 59% of participants had a high school education or less. For 22 dietary nutrients (excluding supplements) and alcohol, the median crude correlation between intakes based on diet records and the food frequency questionnaire completed before the diet records was 0.42; after adjustment for energy, age, and sex, and after correction for attenuation in the correlation coefficients due to error from a limited number of diet records, the median correlation was 0.52. Correlations for men and women were similar. The validity of the food frequency questionnaire in this population was similar to that reported previously and supports the use of self-administered food frequency questionnaires in studies of general populations. PMID: 8347747 [PubMed - indexed for MEDLINE]
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