Atherosclerosis is a disease caused by the buildup of plaque on the artery walls resulting in clogged blood vessels. Approximately 4.6 million individuals are diagnosed with atherosclerosis each year. Additionally, many of these individuals will develop heart disease as a consequence of this condition. Due to the fact that heart disease is the number one cause of death in the United States, preventative and treatment measures must be taken.
Vitamin D is associated with reduced risk of several common cardiovascular disease (CVD) risk factors, including obesity, diabetes, hypertension and atherosclerosis. In addition, vitamin D is known to decrease inflammation and regulate the function of endothelial cells, the cells that line blood vessel walls. Both of these actions are protective against cardiovascular disease.
This meta-analysis explored the role of vitamin D on common carotid artery plaque build-up, an important predictor of atherosclerosis. Plaque build-up can be determined by measuring the thickness of the tunica intima and tunica media, known as intima-media thickness (IMT). The tunica media and tunica intima are the two innermost layers of the arterial wall which can collect plaque as atherosclerosis develops. Higher IMT measurements indicate plaque build-up within the artery walls.
Researchers carefully selected 21 studies to include in this meta-analysis. All of these studies had available data on common carotid artery intima-media thickness (CCA-IMT), and six of them included data on the prevalence of carotid plaque build-up. A total of 3,777 vitamin D deficient patients and 4,792 controls were included in the analysis. Vitamin D deficiency was defined as <20 ng/ml, vitamin D insufficiency as 21-29 ng/ml and vitamin D sufficiency as >30 ng/ml.
Based off the studies included, this is what the researchers found:
- The 3,777 vitamin D deficient patients had significantly higher CCA-IMT measurements compared to the 4,792 vitamin D sufficient individuals (p<0.001).
- In the six studies that compared the CCA-IMT of vitamin D insufficient patients to vitamin D sufficient patients, there was a significantly higher CCA-IMT measurement in the vitamin D insufficient group (p<0.001).
- CCA-IMT measurements increased as vitamin D levels decreased .
- In the six studies that analyzed the prevalence of carotid plaque, the risk of carotid plaques was 37.0% in vitamin D deficient patients and 23.7% in the controls.
- Vitamin D deficient individuals experienced 2.29 times increased odds of developing carotid plaques than those in the control group (OR: 2.25; CI: (95%CI: 1.03-5.11 ).
The researchers concluded,
“… results of our meta-analysis consistently suggest an increased CV risk in patients with vitamin D deficiency, as well as in those with vitamin D insufficiency and suggest the need for a strict monitoring of CV risk factors and of subclinical signs of atherosclerosis in this clinical setting.”
It is important to acknowledge the limitations of this study. Researchers noted that the most significant limitation was variability between exclusion and inclusion criteria that determined cardiovascular risk factors between the studies. Therefore, not all confounding factors were able to be adjusted for. However, while this was not a meta-analysis of randomized controlled trials, this analysis of mostly prospective studies did have a relatively strong study design. In addition, the researchers found a significant heterogeneity between the studies included in the analysis (p<0.001). This means that the studies included were all similar enough to be compared accurately.
Further clinical trials that explore the relationship between vitamin D status and CCA-IMT, as well as carotid plaque prevalence, are needed to validate these findings.
Peterson, R. Meta-analysis finds that vitamin D deficiency is associated with carotid artery intima-media thickness. The Vitamin D Council Blog & Newsletter, 2017.