Cognitive decline is linked to vitamin D deficiency and physical inactivity

The number of seniors is on the rise and so is the number of older people with cognitive decline and dementia. It is a huge health burden and not enough is done to prevent it. According to a large population study published in Frontiers in Nutrition, widespread problems with vitamin D deficiency combined with too little physical activity contribute significantly to an increased risk of cognitive decline and dementia in old age. The authors describe the important interaction between vitamin D and exercise, which is vital for brain health and cognitive health.

According to WHO, the global number of seniors suffering from cognitive decline will increase to around 139 million by the year 2050. Cognitive decline affects the part of our intelligence that is linked to concentration, learning, memory, spatial perception, language skills, and problem solving. Cognitive decline can also be an early stage of Alzheimer’s disease and other types of dementia. Older people are most likely to suffer from cognitive decline, which often takes years to develop. Loss of cognitive functions also affects quality of life, social relations, and the ability to look after oneself. Not surprisingly, cognitive decline comes with a huge human and socio-economic price tag, yet only few and limited treatment strategies and targeted drugs are available. It is therefore especially important to look into potential risk factors and discover how we can prevent cognitive decline among older people in the future. It is already known that physical activity and vitamin D play a key role in cognitive functioning, yet very few studies have looked into this mechanism. In the new study, the researchers therefore wanted to investigate the relation, especially because vitamin D deficiency is so widespread among seniors, and the same goes for physical inactivity.
The current study was conducted on 2,500 men and women aged 60 years and older (with an average age of 69 years). Using the Global Physical Activity Questionnaire, the scientists assessed the physical activity level of the participants. Blood levels of vitamin D were measured, with 50 nmol/L being the lower threshold level for deficiency.
The participants’ cognitive functions were evaluated by means of three different tests. One test is named CERAD-WL (Consortium to Establish a Registry for Alzheimer´s Disease) and measures a person’s learning skills. Another test called AFT (Animal Fluency Test) looks at a person’s ability to remember words and speak fluently. The third test known as DSST (Digit Symbol Substitution Test) looks at the ability to receive information and shift focus. The three tests were used as a criterium for cognitive decline, provided the score was in the lowest quartile.
Afterwards, the researchers made statistical analyses of the comprehensive data to look closer at possible interactions between physical activity, vitamin D, and subgroups of cognitive functions.
According to the results, lack of physical activity is linked to poorer learning skills and an increased risk of cognitive decline as assessed by the CERAD-WL test. Lack of vitamin D is significantly associated with a reduced ability to speak fluently, according to the AFT test, and a reduced ability to receive information and shift focus, according to the DSST test.
The researchers also observed several positive interactions between physical activity and vitamin D, according to the AFT test and the DSST test.
Based on their findings, they conclude that too little physical activity and a lack of vitamin D are significantly correlated to an increased risk of developing cognitive decline in old age. There are also other important interactions between physical activity and vitamin D that are relevant for cognitive functioning.

How does vitamin D affect cognitive functions?

Vitamin D affects our cognitive functions in a variety of ways. Brain cells have vitamin D receptors, which includes cells in the hippocampus, the part of the brain that controls our memory and sense of orientation. Vitamin D also counteracts oxidative stress and chronic inflammation, which can increase the risk of atherosclerosis and damage to nerve cells and other tissues. Also, vitamin D counteracts the build-up of specific proteins in the brain, which is known to lead to Alzheimer’s disease.
Multiple studies have shown that lack of vitamin D is common in old age and contributes to the onset of cognitive decline, dementia, and Alzheimer’s disease. Health authorities therefore recommend that older people take a vitamin D supplement. The problem is that the recommended dose is quite small (10-20 micrograms/day) and not sufficiently high to optimize blood levels of the nutrient. The optimal level should ideally be above 75 nmol/L.

What significance does physical activity have for cognitive functions?

Moderate daily physical activity such as walking, cycling, cleaning, climbing stairs, or gardening can prevent a number of chronic conditions, including the development of cognitive decline. Studies have shown that being physically active on a regular basis can lower the risk of dementia and Alzheimer’s disease by 28 and 45 percent, respectively. The reason for this is that physical activity stimulates blood circulation, including the flow of blood through the brain. It also releases different neurotransmitters such as dopamine, which is linked to well-being and makes it easier for the brain to learn. Also, moderate physical activity is good for preventing mental stress and has a long list of other health benefits. People aged 65 years and older are advised to be physically active for at least 30 minutes every day. Make sure to include activities at least twice weekly that strengthen muscles. Also, train balance and flexibility and try to limit sedentary time.

• Around one billion people worldwide are believed to lack vitamin D, especially older people
• Many older people don’t get enough exercise
• Cognitive decline and dementia are often linked to lifestyle, so we can do a lot to prevent these things

References:

Jing Guo et al. Association of physical activity and vitamin D deficiency with cognitive impairment in older adults: a population based cross-sectional analysis
Frontiers in nutrition

Maryam Ghahremani et al. Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status. Alzheimer´s & Dementia: Diagnosis, Assessment & Disease Monitoring, 2023

Shreeya S Navale et al. Vitamin D and brain health: an observational and Mendelian randomization study. The American Journal of Clinical Nutrition, 2022