Original Contribution  |   July 2017
Effect of Latitude on Vitamin D Levels
Author Notes
• From the Lake Erie College of Osteopathic Medicine in Erie, Pennsylvania (Dr Leary); the Russell Research Institute at Lutheran General Hospital in Downers Grove, Illinois (Ms Zamfirova and Mr Au); and the University of Minnesota in Minneapolis (Dr McCracken).
• Financial Disclosures: None reported.
• Support: Funded by the Lake Erie Consortium for Osteopathic Medical Training (LT51511).
•  *Address correspondence to Patrick F. Leary, DO, MS, 5401 Peach St, Suite 3400, Erie, PA 16509-2601. E-mail: pleary@lecom.edu

Article Information
Medical Education
Original Contribution   |   July 2017
Effect of Latitude on Vitamin D Levels
The Journal of the American Osteopathic Association, July 2017, Vol. 117, 433-439. doi:10.7556/jaoa.2017.089
The Journal of the American Osteopathic Association, July 2017, Vol. 117, 433-439. doi:10.7556/jaoa.2017.089
Abstract

Context: Vitamin D levels have been linked to bone health and to numerous diseases; however, an element that lacks substantial direct data and limits the evidence basis regarding whom to screen for vitamin D deficiency is the effect of latitude on vitamin D levels.

Objectives: To determine whether latitude influences vitamin D levels and to investigate the influence of other factors that may affect vitamin D levels, including sex, race, skin type, and body mass index.

Methods: Osteopathic medical students were recruited from campuses in Bradenton, Florida, and Erie, Pennsylvania. Surveys were administered to obtain demographic information, and blood samples were drawn to measure total vitamin D levels. Two-sample t tests, Fisher exact test, and logistic regression was used to assess differences in total vitamin D levels between the 2 locations.

Results: A total of 359 medical students (aged 22-57 years) were included in the study, 194 at the Bradenton campus and 214 at the Erie campus. The mean (SD) vitamin D level was 34.5 (11.8) ng/mL among participants in Bradenton and 28.1 (12.4) ng/mL among participants in Erie. Logistic regression models revealed an adjusted OR of 3.3 (95% CI, 1.73-6.4) for deficient total vitamin D among Erie students. Non-white race, male sex, and high body mass index were also statistically significant risk factors for vitamin D deficiency in regression models (P<.05).

Conclusion: Latitude was found to be a statistically significant risk factor for vitamin D deficiency. Additionally, the findings suggest that persons with darker skin tone and, to a lesser degree, men and persons who are overweight or obese are also at increased risk for vitamin D deficiency. Physicians should be cognizant of these risk factors when deciding whom to screen.

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