Winning Abstracts from the 2013 Medical Student Abstract Competition: The Relationship Between Serum 25-Hydroxyvitamin D And Peripheral Arterial Disease
Author: David L. Narotsky, MD, Johns Hopkins University School of Medicine, Class of 2013
Introduction: Low serum 25(OH) D levels are associated with higher prevalence of peripheral arterial disease (PAD). It has been proposed that this inverse relationship is non-linear in that the association diminishes with rising 25(OH) D levels. To test this hypothesis, we examined the relationship between 25 (OH) D and PAD as measured by Ankle-Brachial index (ABI) in healthy adult US population.
Methods: We analyzed data from the continuous National Health and Nutrition Examination Survey for years 2001-2004. ABI was treated as a continuous variable and the minimum of the two reported ABI values was chosen for each individual. To examine the non-linear relationship between 25(OH) D and ABI, we introduced a spline, with a single knot at the median serum levels (21ng/mL) of 25(OH) D. The same analysis was performed later with a single spline of 27 ng/ml (75th percentile). The effect of 25(OH) D was calculated for every 10 ng/mL increase below and above each spline. Regression models were adjusted for age, sex, race, body mass index, blood pressure, serum glucose, c-reactive protein, smoking, total cholesterol, and renal function.
Results: Of the 4979 individuals, 48% were females and 58% were Caucasians. The mean (SD) age, 25 (OH) D, c-reactive protein, and ABI was 60.4 (13.22) years, 22.1(8.68) ng/mL, 0.46(0.81) mg/dL and 1.07(0.15), respectively. In both unadjusted and adjusted linear regression models without a spline, we found that 25(OH) D was associated with a significant increase in ABI (0.018, 95% CI: 0.013 to 0.023 and 0.018, 95% CI: 0.012 to 0.024, respectively) for each 10 ng/mL increase in serum 25(OH) D. In the unadjusted linear regression model with spline, any change in ABI with rising serum 25(OH) D was much larger before 21 ng/mL (0.04, 95% CI: 0.03 to 0.05) than after 21 ng/mL (0.01, 95% CI: 0.003 to 0.013), for each 10 ng/mL increase in serum 25(OH) D. In adjusted analysis, the association between ABI and 25(OH) D remained statistically significant before 21 ng/mL (0.04, 95% CI: 0.02 to 0.05 ) but not after 21 ng/mL (0.008, 95% CI: - 0.0008 to 0.017) for each 10 ng/mL increase in 25(OH) D. Once serum 25 (OH) D levels increases above 27 ng/mL (75th percentile), we found no statistically significant increase in ABI in regression analysis adjusted for traditional cardiovascular risk factors.
Conclusions: ABI increases as serum 25(OH) D levels increases, however, the change is nonlinear and it appears to plateau after 21 ng/mL of 25(OH) D and disappear after 27 ng/ml in healthy adults. It is likely that the benefit of 25(OH) D supplementation for the prevention of PAD may only be seen in individuals with 25(OH) D levels below 21 ng/mL.
Students: Join ACP for Free
Benefits of Membership for Students: ACP's free Medical Student Membership includes benefits designed especially to meet students' needs.
Join Now: Sign-up today and begin enjoying the benefits of ACP Medical Student Membership.
Find a Residency
Search ACP's Internal Medicine Residency Database for information on all internal medicine residency programs in the U.S. and Canada. (ACP Members only)
MKSAP 16 Holiday Special: Save 10%
Use MKSAP 16 to earn MOC points, prepare for ABIM exams and assess your clinical knowledge. For a limited time save 10% when you use priority code MK16TOP2!
Will You be Stumped? Try the Consult Guys and Earn Free CME
The Consult Guys have another stumper! How would you handle this case? Watch the video and take the CME quiz.