Dr. Michal L. Melamed of the Albert Einstein College of Medicine in New York and colleagues analyzed vitamin D levels in 13,331 people who participated in the Third National Health and Nutritional Examination Survey. Vitamin D levels were collected between 1988 and 1994, and participants were tracked through 2000.

Some nine years later, 1,806 of the participants had died. The study subjects were divided into four groups -- quartiles -- based on their vitamin D levels. Those in the group with the lowest level, less than 17.8 nanograms per milliliter, had a 26 percent increased rate of death from any cause compared with those in the group with the highest vitamin D levels.

The optimum blood level of 25-hydroxyvitamin D has been suggested to be 30 nanograms per milliliter or higher. Approximately 41 percent of U.S. men and 53 percent of U.S. women have levels lower than 28 nanograms per milliliter, the researchers said.

The findings are published in the Archives of Internal Medicine.