Patients who have been resuscitated after sudden cardiac arrest may at higher risk of poor brain function or death if they are vitamin D deficient. This is according to a study presented at the annual meeting of the Acute Cardiovascular Care Association - a part of the European Society of Cardiology - in Geneva, Switzerland.

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Poor brain function may be seven times more likely in vitamin D deficient patients who have been resuscitated after cardiac arrest.

Vitamin D levels are determined by a 25-hydroxyvitamin D, or 25-(OH) D, blood test. The National Institutes of Health state that an individual's vitamin D levels are normal if they are 30-74 nanograms per milliliter (ng/mL).

However, the definitions of vitamin D deficiency vary. The Vitamin D Council class 0-30 ng/mL as deficient, the Endocrine Society state 0-20 ng/mL as deficient, while the Food and Nutrition Board deem 0-11 ng/mL as deficient.

Since the majority of the body's vitamin D comes from the sun, lack of exposure to sunlight is a major cause of vitamin D deficiency. Other causes include lack of vitamin D in the diet, liver and kidney diseases, and poor food absorption.

Vitamin D deficiency has been linked to an array of health conditions. Earlier this year, Medical News Today reported on a study linking vitamin D deficiency to all-cause mortality and cancer prognosis, while another study suggests vitamin D deficiency may increase the risk of schizophrenia.

Assessing the effects of vitamin D deficiency on outcomes after cardiac arrest

But according to Dr. Jin Wi, co-author of this latest study, researchers have not assessed how vitamin D deficiency affects neurological outcomes following cardiac arrest - when the heart suddenly stops pumping blood around the body.

As such, the research team analyzed the vitamin D levels and outcomes of 53 unconscious patients from the Severance Cardiovascular Hospital in Seoul, Korea, who had been resuscitated following cardiac arrest.

Of these patients, 41 had received cardiopulmonary resuscitation (CPR). They note that the first monitored heart rhythm was shockable in 36 of the patients, while this rhythm was non-shockable in 17 patients.

The researchers used the Cerebral Performance Category (CPC) score to assess patients' neurological outcomes 6 months after they were discharged from the hospital. A score of 1-2 represented a good neurological outcome, while a score of 3-5 was deemed a poor neurological outcome.

The researchers defined patients as vitamin D deficient if their 25-(OH) D levels were below 10 ng/mL.

Vitamin D deficiency linked to seven-fold increased risk of poor brain function

Results of the analysis revealed that 65% of patients with vitamin D deficiency had a poor neurological outcome 6 months after being discharged from the hospital, compared with only 23% who had vitamin D levels in the normal range.

Patients who experienced poor brain function had a much lower average vitamin D level, at 7.9ng/mL, compared with patients who had a good neurological outcome, who had an average vitamin D level of 12.5 ng/mL.

After conducting a logistic analysis of the results, the team calculated that vitamin D deficiency increased the likelihood of a poor brain function after cardiac arrest seven-fold. "The only factors that had a greater impact on poor neurological outcome were the absence of bystander CPR or having a first monitored heart rhythm that was non-shockable," says Dr. Wi.

Furthermore, the team found that 6 months after hospital discharge, 29% of patients who were vitamin D deficient had died, but all of the patients with normal vitamin D levels were still alive.

Commenting on the overall findings, Dr. Wi says:

"Our findings suggest that vitamin D deficiency should be avoided, especially in people with a high risk of sudden cardiac arrest. People are at higher risk if they have a personal or family history of heart disease including heart rhythm disorders, congenital heart defects and cardiac arrest.

Other risk factors for cardiac arrest include smoking, obesity, diabetes, a sedentary lifestyle, high blood pressure and high cholesterol, and drinking too much alcohol."

He added that a large, randomized clinical trial is warranted in order to determine whether vitamin D supplements could reduce the risk of cardiac arrest in high-risk patients.

Past studies, however, have blasted the use of vitamin D supplements for cardiovascular health. Earlier this year, MNT reported on a study suggesting that vitamin D supplements do not prevent heart attack or stroke, although the researchers say there was some evidence they could protect against heart failure in seniors.