Most practitioners believe that low levels of vitamin D could be a factor in many health concerns, especially in cognitive decline and Alzheimer’s disease. While this recent study Monday doesn’t prove that link, it does find that seniors with low vitamin D levels exhibited low thinking skills than those who had adequate vitamin D levels.
Vitamin D is essential for many body functions such as ensuring strong bones by enhancing calcium absorption. In this particular study, researchers wanted to see what type of effect vitamin D levels had on the cognitive function of seniors of various ethnic backgrounds. The study is notable because they looked at the baseline levels of vitamin D in a multi-ethnic group of volunteers and then compared those levels with their cognitive function. They also assessed how the change in cognitive function correlated with vitamin D status over time.
The study consisted of 382 seniors with an average age of 75. More than half (62%) were women. The largest number of participants were white (41%), African American (29.6%) and Hispanic (25%). In terms of cognitive function, at the beginning of the study 49.5% of the participants were cognitively normal, 32.7% were mildly cognitively impaired, and 17.5% had dementia. The investigators measured vitamin D levels with blood (25 OHD).
The participants in this study resided in the Sacramento Valley of California. Researchers followed up with the participants for about 4.8 years which included having them undergo annual neurological exams and neuropsychological testing at the University of California, Davis, Alzheimer’s Disease Center.
Lowest Vitamin D Levels = Greater Rate of Cognitive Decline
Researchers found that the baseline average 25 OHD levels were lower for the African American (17.9 ng/mL) and Hispanic participants (17.2 ng/mL) when they were compared with the white subjects (21.7 ng/mL). They also noted that average 25 OHD levels were lower in the dementia group than in the mildly cognitive impaired and cognitively normal groups (16.2, 20.0 and 19.7 ng/mL, respectively). On follow-up, which averaged 4.8 years, researchers found that subjects who had deficient (less than 12 ng/mL) or insufficient (12 to less than 20 ng/mL) vitamin D status had the largest rates of cognitive decline.
Dr. Miller, in the audio portion of the news release, stated: “About 60% of the group, regardless of their race or ethnicity, was low in vitamin D. Those low in vitamin D declined more in short term memory, known as episodic memory, as well as more complex cognitive tasks, known as executive function. They were declining about two and a half times faster than those who had adequate vitamin D.”
“We expected to see declines in individuals with low vitamin D status,” said Charles DeCarli, director of the Alzheimer’s Disease Center. “What was unexpected was how profoundly and rapidly [low vitamin D] impacts cognition. This is a vitamin deficiency that could easily be treated and that has other health consequences. We need to start talking about it. And we need to start talking about it, particularly for people of color, for whom vitamin D deficiency appears to present an even greater risk.”
The study didn’t look at whether taking vitamin D supplements could prevent decline. The researchers call for more studies to determine whether vitamin D supplements can slow cognitive decline.
Miller J, et al. Vitamin D Status and Rates of Cognitive Decline in a Multiethnic Cohort of Older Adults. JAMA Neurol. Published online September 8, 2015. doi:10.1001/jamaneurol.2015.211