British Journal of Nutrition

Full Papers

Dietary Survey and Nutritional Epidemiology

Racial and seasonal differences in 25-hydroxyvitamin D detected in maternal sera frozen for over 40 years

Lisa M. Bodnara1a2a3a4 c1, Janet M. Catova1a2a4, Katherine L. Wisnera1a2a3a4 and Mark A. Klebanoffa5

a1 Department of Epidemiology, University of Pittsburgh Graduate School of Public Health, A742 Crabtree Hall, 130 DeSoto Street, Pittsburgh, PA 15261, USA

a2 Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

a3 Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

a4 Magee-Women's Research Institute, Pittsburgh, PA, USA

a5 Division of Epidemiology, Statistics and Prevention Research, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA

Abstract

Serum banks from large, decades-old epidemiological studies provide a valuable opportunity to explore the contributions of in utero vitamin D exposure to fetal origins of adult diseases. We compared 25-hydroxyvitamin D (25(OH)D) by race and season (two powerful predictors of vitamin D status) in sera frozen for ≥  40 years with sera frozen for ≤  2 years to determine whether 25(OH)D is stable enough to test vitamin D-related hypotheses. Data and sera came from seventy-nine pregnant women at 29–32 weeks' gestation in the Boston Collaborative Perinatal Project (CPP; 1959–66) and 124 women at 20–36 weeks' gestation in a 2003–2006 Pittsburgh cohort study. Multivariable linear regression models were used to test main and joint effects of race and season after confounder adjustment. In both cohorts, serum 25(OH)D levels were lower among black than white women (CPP 33·3 v. 46·7 nmol/l, P < 0·01; Pittsburgh 47·1 v. 89·6 nmol/l; P < 0·0001) and in winter than summer (CPP 32·7 v. 47·6 nmol/l, P < 0·0001; Pittsburgh 66·7 v. 89·8 nmol/l, P < 0·001), with no evidence of a race × season interaction in either cohort. Differences remained significant after confounder adjustment. When CPP and Pittsburgh results were compared, there was no significant difference in the race or season effects. The similarity in the relative change in 25(OH)D in these cohorts by two powerful predictors of vitamin D status suggests that, even if 25(OH)D deteriorated somewhat, it did so similarly across samples. Therefore, trends could be obtained from the decades-old serum data that would be relevant in exploring vitamin D-related hypotheses in future studies.

(Received July 16 2007)

(Revised March 14 2008)

(Accepted March 17 2008)

(Online publication April 23 2008)

Correspondence:

c1 Corresponding author: Dr Lisa M. Bodnar, fax +1 412 624 7397, email bodnar@edc.pitt.edu

Footnotes

Abbreviations: ADUP, Antidepressant Use during Pregnancy; CPP, Collaborative Perinatal Project; IDS, Immunodiagnostic Systems Limited; 25(OH)D, 25-hydroxyvitamin D

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