Older adults who struggle with both poor sleep and early memory problems may have a higher risk of future cognitive decline.
New research from Emory University suggests that higher vitamin D supplement intake may be associated with stronger thinking skills in this vulnerable group.
The study was published in Sleep Medicine and involved 54 adults with mild cognitive impairment and sleep disturbances. Researchers found that people who reported taking at least 5,000 IU of vitamin D each day performed better on a commonly used cognitive screening test.
Vitamin D is a nutrient the body needs for several basic functions. It helps maintain healthy bones and muscles, supports nerve activity, and plays a part in immune function.
The body can make vitamin D when skin is exposed to sunlight, and smaller amounts also come from foods and supplements. Some people, especially older adults, may have low vitamin D because they spend less time outdoors, absorb nutrients less efficiently, or have other health conditions.
Scientists have been studying whether vitamin D may also affect the brain. Previous research has reported links between low vitamin D levels and poorer memory, dementia risk, depression, and sleep problems, but the evidence has been mixed.
The Emory researchers focused on a group that may be especially important to study. All participants had mild cognitive impairment, a condition in which memory or thinking problems are noticeable but not severe enough to be classified as dementia.
They also had sleep disturbances. Sleep is important for attention, memory formation, emotional balance, and many repair processes in the body, so poor sleep may place extra strain on people who are already experiencing cognitive changes.
To measure thinking ability, the researchers used the Montreal Cognitive Assessment. This short test evaluates memory, concentration, language, visual skills, and the ability to plan or solve simple problems.
Participants who took 5,000 IU or more of vitamin D each day scored more than 13% higher than those who took no vitamin D supplements. The researchers reported that this difference remained after taking other possible influences into account.
Smaller daily doses were not linked with the same improvement. That does not necessarily mean lower doses are ineffective, because the study was small and was not designed to find the best dose for brain health.
The team also examined the two main forms of vitamin D found in supplements. Vitamin D2 usually comes from plant or fungal sources, while vitamin D3 is commonly produced from animal sources and is also the form made in human skin after sun exposure.
No clear difference in cognitive performance was seen between people taking D2 and those taking D3. In other words, the total amount of vitamin D appeared more important than the form in this analysis.
The researchers believe timing may be important. Mild cognitive impairment can represent a stage between normal aging and dementia, so it may be a period when lifestyle or medical changes have a better chance of making a difference.
Senior author Victoria Pak of Emory University’s Nell Hodgson Woodruff School of Nursing said identifying changeable factors at this stage could become increasingly important as Alzheimer’s disease becomes more common. The number of Americans living with Alzheimer’s dementia is expected to approach 13 million by 2050.
Sleep adds another layer to the story. Around half of people with moderate to severe Alzheimer’s disease experience significant sleep problems, and scientists increasingly think the relationship can work in both directions.
Poor sleep may contribute to worsening brain health, while changes in the brain may also make normal sleep harder. Vitamin D has been linked in earlier studies to sleep-wake regulation, although researchers still do not fully understand the connection.
The new findings are promising, but they are far from proof that high-dose vitamin D can prevent dementia. Only 54 people were studied, and participants were not randomly assigned to vitamin D or placebo groups.
That means other differences between supplement users and non-users may explain some of the result. People who take supplements regularly may also be more likely to exercise, eat well, attend medical appointments, or manage chronic disease.
There is also a practical safety concern. Taking 5,000 IU every day is above the standard recommended intake for most adults, and long-term excessive vitamin D can cause high calcium levels, kidney stones, or other complications.
Because of this, the study should not be read as advice for everyone with memory or sleep problems to take a high dose. Larger clinical trials are needed to test whether vitamin D itself improves cognition and to identify which people, if any, are most likely to benefit.
Overall, this early study adds to the growing interest in vitamin D as a possible part of brain health. For now, its main value is in identifying a question worth testing more carefully rather than proving a new treatment for dementia.
Source: Emory University.
