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Vitamine D en cognitieve achteruitgang*
Uit een Canadese studie blijkt dat goede bloedwaarden vitamine D belangrijk zijn bij het ouder worden om cognitieve achteruitgang tegen te gaan. In de studie werd bij 752 vrouwen van 75 jaar en ouder bloedwaarden vitamine D vastgesteld en een uitvoerige cognitieve test uitgevoerd. Zij met de laagste bloedwaarden vitamine D ( < 10 ng/ml) hadden een duidelijk slechtere cognitieve testuitslagen. Volgens de onderzoekers is het al algemeen bekend dat het merendeel van de mensen te lage bloedwaarden vitamine D hebben doch bij ouderen ligt dat percentage wel op 70-80%.
Vitamin D Deficiency Linked to Cognitive Impairment in Older Women
Vitamin D deficiency appears to increase the risk for cognitive impairment, a large, population-based study of older women shows.
Presented here at the American Academy of Neurology 62nd Annual Meeting, the cross-sectional study shows older women with serum 25-hydroxyvitamin D (25OHD) levels of less than 10 ng/mL had a 2-fold increased risk of global cognitive impairment compared with their counterparts who were not vitamin D deficient.
"After accounting for all potential confounders, our findings showed an association between vitamin D deficiency and global cognitive impairment. These results are congruent with fundamental research and add to the growing body of evidence in favor of the neurological action of vitamin D," principal investigator, CÚdric Annweiler, MD, Angers University Hospital in France, told Medscape Psychiatry.
Dr. Annweiler said he became interested in looking at the potential impact of vitamin D on cognitive function when studying risk factors associated with falling in older women in the Epidemiologie de l'Osteoporose (EPIDOS) study. This large, prospective, observational, multicenter cohort study was designed to evaluate risk factors for hip fracture among more than 7500 healthy, community-dwelling older women.
Typically associated with skeletal disorders, vitamin D deficiency is also associated with neuromuscular disorders in humans and severe coordination disorders in animal research, said Dr. Annweiler.
Specific CNS Effects
A neurosteroid hormone, research shows it has specific effects on the central nervous system (CNS), including regulation of neurotransmission, neuroimmunomodulation, and neuroprotection.
According to Dr. Annweiler, few studies have investigated the association between low serum 25OHD and cognitive impairment. A recent systematic review of the literature conducted by his team produced mixed results (Eur J Neurol. 2009;16:1083-1089).
However, the investigators speculated that these inconclusive findings may be explained by the lack of control for potential confounders.
To determine whether there was an association between vitamin D deficiency and global cognitive impairment, the investigators studied 752 women from the EPIDOS cohort. Participants were 75 years and older and were divided into 2 groups according to serum 25OHD concentration - deficient (<10 ng/mL) or nondeficient (=10 ng/mL).
Cognitive impairment was determined using the Pfeiffer Short Portable Mental State Questionnaire (SPMSQ), a validated, 10-item, composite questionnaire used to screen for organic brain diseases. Cognitive impairment was defined as an SPMSQ score of less than 8.
Investigators controlled for a variety of potential confounders, including age, body mass index, number of chronic diseases, current hypertension, current depression, use of psychoactive drugs, education level, regular physical activity, and serum intact parathyroid hormone and calcium.
Rampant Problem in the Elderly
The results showed that compared with women who were not vitamin D deficient (n = 623) their vitamin D deficient counterparts had a lower mean SPMSQ score (P < .001) and were also more likely to have an SPMSQ score of less than 8 (P = .006).
Adjusted analysis revealed that vitamin D was significantly associated with cognitive impairment (odds ratio, 2.03; P = .001).
The clinical implications, said Dr. Annweiler, appear clear - clinicians need to assess and treat vitamin D deficiency in their older patients for a variety of health reasons that may include preservation of cognitive function.
Vitamin D deficiency is common in the general population but is rampant among the elderly. According to Dr. Annweiler, it is estimated that 70% to 80% of individuals older than 75 years are vitamin D deficient.
Currently, adequate intakes of vitamin D for 51- to 70-year-olds are 400 IU per day and 600 IU for those older than 70 years to maintain a 25OHD level of 30 ng/mL or more. However, Dr. Annweiler noted that these recommendations are based primarily on preservation of bone health alone.
The reason the elderly are more vulnerable to vitamin D deficiency than younger individuals are several-fold and include decreased exposure to sunlight and inadequate dietary intake. In addition, said Dr. Annweiler, the skin of older people is not as efficient at synthesizing UV-B rays into vitamin D.
"This study provides more evidence to support [vitamin D] supplementation in our elderly patients to normalize serum concentrations and help sustain good health. Although we are not certain yet, it may be that this will also be a viable way to prevent or treat cognitive impairment and possibly turn out to be a new management strategy for dementia," said Dr. Annweiler.
The study was initially published earlier this year in Neurology. At that time, in an accompanying editorial, Joshua W. Mill, PhD, UC Davis Medical Center, Sacramento, California, echoed Dr. Annweiler's clinical recommendation (Neurology. 2010;74:13-15).
What are needed now are placebo-controlled intervention studies to determine whether vitamin D supplements will protect against age-related cognitive decline. In the meantime, neurologists and geriatricians should be aware of the high prevalence of vitamin D deficiency in their patient populations and the possibility that supplementation could be beneficial," Dr. Mill writes.
Dr. Annweiler said his team plans to prospectively follow up the cohort and examine the potential relationship between vitamin D status and incident dementia. In addition, his team is exploring the possibility of conducting a clinical trial to look at the impact of supplementation on cognitive outcomes.
The study was funded by the French Ministry of Health. Dr. Annweiler and Dr. Miller have disclosed no relevant financial relationships.
American Academy of Neurology (AAN) 62nd Annual Meeting: Abstract S34.003. (Maart 2011)