a1 Department of Community Health and Epidemiology, Cancer Research Institute, Queen's University, Kingston, ON K7L 3N6, Canada
a2 Division of Cancer Care and Epidemiology, Queen's Cancer Research Institute, Queen's University, Kingston, Ontario, Canada
a3 Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
a4 School of Nursing, Queen's University, Kingston, Ontario, Canada
Objective In 2011, the US Institute of Medicine updated the definition of vitamin D inadequacy to serum 25-hydroxyvitamin D (25(OH)D) concentration of 30–<50 nmol/l and of deficiency to serum 25(OH)D < 30 nmol/l. We describe the prevalence of these conditions according to these definitions, seasonal variation in 25(OH)D and predictors of serum 25(OH)D concentrations among working, white women.
Design Participants recorded lifestyle factors and dietary intake and provided fasting blood samples for measurement of serum 25(OH)D in both summer and winter. Predictors of serum 25(OH)D variation were analysed using linear regression and generalized linear mixed models.
Setting Kingston General Hospital in Kingston, Ontario, Canada, from April 2008 to July 2009.
Subjects Female premenopausal nurses (n 83) working full-time rotating shifts.
Results Deficient or inadequate vitamin D status was observed in 9 % of participants following summer/autumn and in 13 % following winter/spring. Predictors of serum 25(OH)D concentration were vitamin D supplement use, tanning bed use and season. Tanning bed use increased serum 25(OH)D by 23·24 nmol/l (95 % CI 8·78, 37·69 nmol/l, P = 0·002) on average.
Conclusions According to the 2011 Institute of Medicine bone health guidelines, over 10 % of nurses had deficient or inadequate vitamin D status following winter. Higher serum concentrations were associated with use of tanning beds and vitamin D supplements. As health promotion campaigns and legal restrictions are successful in reducing tanning bed use among women, our data suggest that increased prevalence of vitamin D inadequacy and deficiency may be a consequence, and that low vitamin D status will need to be countered with supplementation.
(Received February 13 2013)
(Revised May 03 2013)
(Accepted May 20 2013)
(Online publication July 09 2013)
† Both affiliations are former affiliations of the author.