Low Vitamin D Linked To Greater Risk of Death

Just-published study indicates how patients with vitamin D deficiency have higher risk of death

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CEO SUMMARY: A new report in the Archives of Internal Medicine is likely to further spur demand for vitamin D testing. Already, labs are dealing with a dramatic increase in testing for vitamin D deficiency, with test volumes more than doubling in the past 12 months. This new research is considered the most definitive to date. Media reports are educating patients about these findings. Laboratories have an opportunity to ensure that they are running the most appropriate tests for vitamin D deficiency.

PATIENTS WITH LOW LEVELS OF vitamin D appear to have a higher risk of death from all causes, according to a new study published in the August 11/25 issue of Archives of Internal Medicine (AIM). These, and similar findings, are expected to fuel greater demand by patients and physicians for vitamin D testing.

In what is believed to be the most conclusive evidence to date, researchers reported that inadequate levels of vitamin D lead to substantially increased risk of death and can be a contributing factor in cardiovascular disease, diabetes, cancer, and death from other causes. This research was given wide play in newspapers across the nation last week.

The research was conducted and published by clinicians at the Albert Einstein College of Medicine, in the Bronx, New York, and Johns Hopkins University in Baltimore, Maryland. Researchers said the optimum blood level of 25-hydroxyvitamin D (25[OH]D) should be 30 nanograms per milliliter (ng/ml) or higher. According to the study, about 41% of men and 53% of women in the United States have levels lower than 28 nanograms per milliliter.

This incidence of vitamin D deficiency is consistent with the experience of ARUP Laboratories of Salt Lake City, Utah. According to A. Wayne Meikle, M.D., Medical Director of the Endocrinology and Automated Endocrinology Laboratory at ARUP, data in the ARUP database shows 58% of the vitamin D 25 assays done last year were below 30 ng/ml level. Meikle also is a Professor of Medicine, Endocrinology, and Pathology at the University of Utah School of Medicine.

58% Below 30 ng/ml

Like other labs across the United States, ARUP has seen the volume of vitamin D tests increase over the past 12 months. In the last issue of THE DARK REPORT, Meikle noted that numbers in ARUP’s database reveals that vitamin D testing shot up by 248% from an average of about 33,000 vitamin D deficiency tests per month in 2007 to an average of about 82,000 vitamin D deficiency tests per month in 2008.

Meikle has advice for labs that offer vitamin D deficiency testing. “There are assays in the market that do not accurately measure D2, 25OH, so be careful,” he noted. “ARUP uses an assay that measures both D2 and D3 25OH accurately to give a reliable total vitamin D 25. For patients who are deficient, we usually measure vitamin D 25OH two to three months after we begin correcting the deficiency.”

13,331 Patients Studied

For the article in the Archives of Internal Medicine, Michal L. Melamed, M.D., M.H.S., of the Albert Einstein College of Medicine, Bronx, N.Y., and colleagues analyzed vitamin D levels in 13,331 individuals who participated in the Third National Health and Nutritional Examination Survey (NHANES III), conducted by the federal Centers for Disease Control and Prevention.

Vitamin D levels were collected between 1988 and 1994, and participants were tracked through 2000, the researchers said. The other researchers were Erin D. Michos, M.D., MHS; Wendy Post, M.D., MS; and Brad Astor, Ph.D., of the Johns Hopkins University, School of Medicine and the Johns Hopkins Bloomberg School of Public Health, in Baltimore, Maryland.

Tracking Patient Outcomes

Over a median (midpoint) of 8.7 years of follow-up, 1,806 of the participants died, the article said. When the patients were divided into four quartiles based on their vitamin D levels, those in the group with the lowest level (meaning they had less than 17.8 ng/ml) had a 26% increased rate of death from any cause compared with those in the group with the highest vitamin D levels. The authors concluded that the category of patients with less than 17.8 ng/ml is associated with a higher risk of all-cause mortality in the general U.S. population. At the same time, researchers found no significant associations when vitamin D levels were assessed against the risk of death from cardiovascular disease or cancer alone.

“Low vitamin D levels may be associated with death through their effect on blood pressure, the body’s ability to respond to insulin, obesity, and diabetes risk,” the authors said. “Several lines of evidence support vitamin D’s role in risk of death, including the fact that cardiovascular events are more common in the winter, when vitamin D levels are lower, and that cancer survival is better if the disease is diagnosed in the summer when levels are higher.

“Further observational studies are needed to confirm these findings and establish the mechanisms underlying these observations,” the researchers added. “If confirmed, randomized clinical trials will be needed to determine whether vitamin D supplementation at higher doses could have any potential benefit in reducing future mortality risk in those with 25(OH)D deficiency.”

A Rising Wave Of Testing

THE DARK REPORT observes that the increased volume of vitamin D testing reported by labs across the country may be only the front edge of an expanding demand for such tests. Evidence, such as the just-published clinical study referenced in this intelligence briefing, is accumulating that, as the researchers identified earlier wrote “the lowest quartile of 25(OH)D level (<17.8 ng/mL) is independently associated with all-cause mortality in the general population.”

How the American healthcare system responds to this situation will be informative for lab directors and pathologists. First, will evidence-based medicine (EBM) guidelines be quickly developed and introduced to guide clinicians? Second, will payers reimburse laboratories adequately, even in the face of a doubling and tripling in the volume of vitamin D tests being performed?

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