New research suggests that older adults with vitamin D deficiency may experience cognitive decline and impaired performance faster than those with adequate vitamin D levels, Reuters Health reported.

Researchers at the University of California-Davis and Rutgers University found that seniors with low vitamin D declining at a rate three times faster than those with adequate vitamin D levels.

"We were not particularly surprised by our findings because there is a recent and growing literature on the associations between vitamin D status and risk of Alzheimer's disease/dementia, cognitive decline, and brain atrophy," Dr. Joshua W. Miller from Rutgers University told Reuters Health.

For the study, researchers collected and analyzed data from more than 300 people in Northern California participating in longitudinal research at the Alzheimer's Disease Center in Sacramento, Calif. The participants had a mean age of 76 and were either cognitively normal, had mild cognitive impairment, or dementia. They were followed for at least five years.

They found that older adults who had low levels of vitamin D experienced cognitive declines that were two-to-three times faster than those with adequate serum vitamin D levels. In other words it took only two years for the deficient individuals to decline as much as their counterparts with adequate Vitamin D declined during the five-year follow-up period.

"We expected to see declines in individuals with low vitamin D status," Charles DeCarli, director of the Alzheimer's Disease Center, said in a statement. "What was unexpected was how profoundly and rapidly [low vitamin D] impacts cognition."

Researchers also found that African-Americans and Latinos had a higher risk of accelerated cognitive decline because they "have higher concentrations of melanin, which makes their skin darker, but this inhibits synthesis of vitamin D," HealthDay reported.

Vitamin D deficiency and insufficiency were prevalent among all of the study participants. Overall, 26 percent were deficient and 35 percent were insufficient. Among Caucasians, 54 percent had low vitamin D, compared with 70 percent of African-Americans and Hispanics.

The findings are detailed in the journal JAMA Neurology.