By Sarah Madden, MSc, BSc, February 1st, 2009, abstracted from "Serum 25-Hydroxyvitamin D Concentration and Cognitive Impairment” in the Journal of Geriatric Psychiatry Neurology.

Consuming vitamins is an important part of maintaining good health. Optimal cognitive function is an essential part of maintaining excellent health; however, cognitive function inevitably declines with age. Neurodegenerative diseases such as Alzheimer’s disease [AD] and dementia negatively affect cognitive function and are increasing as the American population continues to age (1).

AD is the most common form of dementia in older individuals (2) and affects approximately 5.2 million Americans (3). It is the 6th leading cause of death and costs approximately $148 billion year (3). The onset of AD usually occurs after the age of 65; however, it may begin earlier (3). Early-onset AD is usually caused by genetic mutations on three identified genes (1). Symptoms of AD include loss of cognitive and motor functions, which include short-term memory, vocabulary and organizational skills (4).

Vitamin D has been shown to have many different biological effects which positively influence health (5). A recent study set out of investigate a possible link between vitamin D and cognitive impairment (6). The researchers found that in 1766 adults aged 65 and older, higher vitamin D status was associated with lower cognitive decline, as measured on the Abbreviated Mental Test Score [AMTS]. The AMTS is a cognitive assessment survey that primarily measures attention, memory and orientation in time and space.

Subjects were divided into cognitively normal and cognitively impaired groups, based on the AMTS assessment . Those who were cognitively impaired were significantly older, were more likely to have less education and to consume higher amounts of alcohol compared to non-cognitively impaired individuals. Cognitively impaired subjects also had significantly
[p < 0.001] higher rates of stroke and lower serum vitamin D concentrations. The relationship between cognitive decline and higher rates of stroke and lower serum D levels was stronger in men and was also associated with higher body mass index [BMI].

This study adds to a body of evidence regarding vitamin D and cognitive function. Vitamin D status is also associated with increased risk of cardiovascular diseases [CVD] which includes stroke as shown by the latest National Health and Nutrition Examination Survey [NHANES] (7). Furthermore, AD incidence is associated with higher cholesterol levels mid-life which also serves as a risk factor for CVD (8). This suggests that vitamin D, AD and variants of CVD may all be related. Further studies should look at possible mechanisms linking low vitamin D status to these diseases.

References

1. National Institute of Neurological Disorders and Stroke: National Institutes of Health. NINDS Dementia Home Page. http://www.ninds.nih.gov/disorders/dementias/dementia.htm
2. National Institute on Aging: National Institutes of Health. Alzheimer’s Disease: Fact Sheet. http://www.nia.nih.gov/NR/rdonlyres/7DCA00DB-1362-4755-9E87-96DF669EAE20/11209/84206ADEARFactsheetAlzDiseaseFINAL08DEC23.pdf
3. Alzheimer’s Association. 2008 Alzheimer’s Disease Facts and Figures. http://www.alz.org/national/documents/report_alzfactsfigures2008.pdf
4. National Institute on Aging: National Institutes of Health. Understanding Stages and Symptoms of Alzheimer’s Disease. http://www.nia.nih.gov/Alzheimers/Publications/stages.htm
5. Garland CF, Garland FC, Gorham ED, Lipkin M, Newmark H, Mohr SB, Holick MF. The role of vitamin D in cancer prevention. Am J Public Health. 2006 Feb;96(2):252-61. Epub 2005 Dec 27. 6. Llewellyn DJ, Langa K, Lang I. Serum 25-Hydroxyvitamin D Concentration and Cognitive Impairment. J Geriatr Psychiatry Neurol. 2008 Dec 10. [Epub ahead of print]
7. Kim DH, Sabour S, Sagar UN, Adams S, Whellan DJ. Prevalence of hypovitaminosis D in cardiovascular diseases (from the National Health and Nutrition Examination Survey 2001 to 2004). Am J Cardiol. 2008 Dec 1;102(11):1540-4.
8. Hirsch-Reinshagen V, Burgess BL, Wellington CL. Why lipids are important for Alzheimer disease Mol Cell Biochem. 2008 Dec 31.