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American Journal of Epidemiology Advance Access published online on June 25, 2008
American Journal of Epidemiology, doi:10.1093/aje/kwn163
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American Journal of Epidemiology © The Author 2008. Published by the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org.

Original Contribution

Frequency of Leisure-Time Physical Activity and Serum 25-Hydroxyvitamin D Levels in the US Population: Results from the Third National Health and Nutrition Examination Survey

Robert Scragg1 and Carlos A. Camargo, Jr2

1 School of Population Health, University of Auckland, Auckland, New Zealand
2 Massachusetts General Hospital, Harvard Medical School, Boston, MA

Correspondence to Dr. Robert Scragg, School of Population Health, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand (e-mail: r.scragg{at}auckland.ac.nz).

Received for publication November 29, 2007. Accepted for publication March 4, 2008.

The decline in vitamin D status among older people is probably due to decreased synthesis of vitamin D by sun-exposed skin and/or decreased outdoor activity. The authors examined the association between outdoor leisure physical activity and serum 25-hydroxyvitamin D in the Third National Health and Nutrition Examination Survey (1988–1994) (n = 15,148 aged ≥20 years). The mean 25-hydroxyvitamin D concentration declined with increasing age, with 79, 73, and 68 nmol/liter for persons aged 20–39, 40–59, and 60 or more years. The proportion that engaged in outdoor activity in the past month was 80% for persons aged 20–39 and 40–59 years but 71% for those aged 60 or more years. In contrast, the mean difference in 25-hydroxyvitamin D between those who participated in outdoor activities daily compared with those who did not participate in the past month was similar for the youngest and oldest age groups: 13 and 16 nmol/liter, respectively. Those persons aged 60 or more years who participated in daily outdoor activities had a mean 25-hydroxyvitamin D concentration similar to that of persons aged 20–39 years: 77 versus 79 nmol/liter, respectively. These nationally representative data suggest that persons aged 60 or more years can synthesize enough vitamin D from daily outdoor activities to maintain vitamin D levels similar to those of young adults.

aged; ethnic groups; exercise; vitamin D

Abbreviations: NHANES III, Third National Health and Nutrition Examination Survey

Editor's note: An invited commentary on this article appears on page 000, and the authors' response appears on page 000.


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