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Gail MH, Wu J, Wang M, Yaun SS, Cook NR, Eliassen AH, McCullough ML, Yu K, Zeleniuch-Jacquotte A, Smith-Warner SA, Ziegler RG, Carroll RJ. Calibration and seasonal adjustment for matched case-control studies of vitamin D and cancer. Stat Med 2016; 35:2133-48. [PMID: 27133461 DOI: 10.1002/sim.6856] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Revised: 11/09/2015] [Accepted: 12/02/2015] [Indexed: 12/17/2022]
Abstract
Vitamin D measurements are influenced by seasonal variation and specific assay used. Motivated by multicenter studies of associations of vitamin D with cancer, we formulated an analytic framework for matched case-control data that accounts for seasonal variation and calibrates to a reference assay. Calibration data were obtained from controls sampled within decile strata of the uncalibrated vitamin D values. Seasonal sine-cosine series were fit to control data. Practical findings included the following: (1) failure to adjust for season and calibrate increased variance, bias, and mean square error and (2) analysis of continuous vitamin D requires a variance adjustment for variation in the calibration estimate. An advantage of the continuous linear risk model is that results are independent of the reference date for seasonal adjustment. (3) For categorical risk models, procedures based on categorizing the seasonally adjusted and calibrated vitamin D have near nominal operating characteristics; estimates of log odds ratios are not robust to choice of seasonal reference date, however. Thus, public health recommendations based on categories of vitamin D should also define the time of year to which they refer. This work supports the use of simple methods for calibration and seasonal adjustment and is informing analytic approaches for the multicenter Vitamin D Pooling Project for Breast and Colorectal Cancer. Published 2016. This article has been contributed to by US Government employees and their work is in the public domain in the USA.
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Affiliation(s)
- Mitchell H Gail
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, U.S.A
| | - Jincao Wu
- Division of Biostatistics, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD, U.S.A
| | - Molin Wang
- Department of Biostatistics, Harvard T. H. Chan School of Public Health, Boston, MA, U.S.A.,Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, U.S.A
| | - Shiaw-Shyuan Yaun
- Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, MA, U.S.A
| | - Nancy R Cook
- Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, U.S.A.,Division of Preventive Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, U.S.A
| | - A Heather Eliassen
- Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, U.S.A.,Channing Division of Network Medicine, Department of Medicine, Brigham and Womens Hospital and Harvard Medical School, Boston, MA, U.S.A
| | | | - Kai Yu
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, U.S.A
| | - Anne Zeleniuch-Jacquotte
- Department of Population Health and Perlmutter Cancer Center, New York University School of Medicine, New York, NY, U.S.A
| | - Stephanie A Smith-Warner
- Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, U.S.A.,Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, MA, U.S.A
| | - Regina G Ziegler
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, U.S.A
| | - Raymond J Carroll
- Department of Statistics, Texas A&M University, College Station, TX, U.S.A.,Department of Mathematics and Statistics, University of Technology, Sydney, Australia
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