Ann Epidemiol. 2011 Mar 16.
Kluczynski MA, Lamonte MJ, Mares JA, Wactawski-Wende J, Smith AW, Engelman CD, Andrews CA, Snetselaar LG, Sarto GE, Millen AE.
Department of Social and Preventive Medicine, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY (M.A.K., A.E.M., M.J.L., J.W.); Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI (J.A.M.); Outcomes Research Branch, Applied Research Program, Cancer Control and Population Sciences, National Cancer Institute, 6130 Bethesda, MD (A.W.S.); Department of Population Health Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI (C.D.E.); Department of Biostatistics, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY (C.A.A.); Departments of Community and Behavior Health and Epidemiology, College of Public Health, the University of Iowa, Iowa City, IA (L.G.S.); and Department of Obstetrics & Gynecology, University of Wisconsin School of Medicine and Public Health, Madison, WI (G.E.S.).
PURPOSE: To investigate whether the association between physical activity and serum 25-hydroxyvitamin D (25(OH)D) concentrations is independent of sun exposure, body size, and other potential explanatory variables.
METHODS: By using data from a sample of 1343 postmenopausal women from the Women's Health Initiative, we used linear regression to examine the associations of duration (minutes/week) of recreational activity and of yard work with 25(OH)D concentrations (nmol/L).
RESULTS: In age-adjusted analyses, positive associations were observed between 25(OH)D concentrations and both duration of recreational physical activity (? = 0.71, SE 0.09, p <.001) and yard work (? = 0.36, SE 0.10, p = .004). After further adjustment for vitamin D intake, self-reported sunlight exposure, waist circumference, and season of blood draw, 25(OH)D was significantly associated with recreational activity (? = 0.21, SE 0.09, p = .014) but not with yard work (? = 0.18, SE 0.09, p = .061). Interactions were observed between season and both recreational activity (P(interaction) = .082) and yard work (P(interaction) = .038) such that these activity-25(OH)D associations were greater during summer/fall compared with winter/spring. Self-reported sunlight exposure and measures of body size did not modify the associations.
CONCLUSIONS: The observed age-adjusted activity-25(OH)D associations were attenuated after adjusting for explanatory variables and were modified by season of blood draw. Adopting a lifestyle that incorporates outdoor physical activity during summer/fall, consuming recommended amounts of vitamin D, and maintaining a healthy weight may improve or maintain vitamin D status in postmenopausal women.
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