You are using an outdated browser. Please upgrade your browser to improve your experience.
Become a Fellow
ACP offers a number of resources to help members make sense of the MOC requirements and earn points.
Understanding MOC Requirements
Earn MOC points
The most comprehensive meeting in Internal Medicine.
April 11-13, 2019
Internal Medicine Meeting 2019
Prepare for the Certification and Maintenance of Certification (MOC)
Exam with an ACP review course.
Board Certification Review Courses
MOC Exam Prep Courses
Treating a patient? Researching a topic? Get answers now.
Visit AnnalsLearn More
Visit MKSAP 17 Learn More
Visit DynaMed Plus
Ensure payment and avoid policy violations. Plus, new resources to help you navigate the Medicare Access and CHIP Reauthorization Act of 2015 (MACRA).
Access helpful forms developed by a variety of sources for patient charts, logs, information sheets, office signs, and use by practice administration.
ACP advocates on behalf on internists and their patients on a number of timely issues. Learn about where ACP stands on the following areas:
© Copyright 2018 American College of Physicians. All Rights Reserved. 190 North Independence Mall West, Philadelphia, PA 19106-1572
Toll Free: (800) 523.1546 · Local: (215) 351.2400
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.
September 2013 Issue of IMpact