Low levels of vitamin D appear to increase the risk of death in older adults, researchers report in the Journal of the American Geriatrics Society.
Skin produces vitamin D when directly exposed to the sun. But older people, particularly those living in northern regions, rarely obtain sufficient sun exposure for adequate vitamin D production and need supplements to achieve healthy vitamin D levels.
Increasingly, evidence points to health risks from inadequate vitamin D.
In the current study, Dr. Adit A. Ginde, at the University of Colorado Denver, in Aurora, and colleagues assessed the risk for death, according to vitamin D levels, in 3,408 men and women who were 73 years old on average when they participated in the Third National Health and Nutrition Examination Survey, or NHANES III.
During more than 7 years of follow-up, 1,493 people died — nearly 44 percent. A little more than half of the deaths were due to heart disease.
After taking into account a variety of factors that could influence the results, low vitamin D was independently associated with an increased risk of death from any cause, but particularly from heart disease, the researchers found.
Optimal vitamin D levels are considered to be somewhere between 80 and 110 or 120 nmol/L (nanomoles per liter) of blood, although there are no set guidelines. On average, people in the current study had vitamin D levels of 66.0 nmol/L of blood.
Ginde's team found that, the risk of death from any cause was 83 percent higher among people with vitamin D levels less than 25 nmol/L, compared with people with vitamin D levels of 100 nmol/L or higher.
The risk of death was 47 percent higher among those with vitamin D levels between 25 and 49.9 nmol/L, relative to those with vitamin D levels of 100 or higher.
Low vitamin D levels, were particularly hard on the heart, the researchers note, with the risk of death due to heart disease more than twofold higher in people with vitamin D levels less than 25 nmol/L.
Current vitamin D recommendations for people 65 years and older appear inadequate, Ginde and colleagues note in their report, and they suggest large scale research to determine the effects of higher-dose vitamin D supplementation.