The study, published in The Journals of Gerontology Series A, examined data from more than 1,200 elderly Chinese people over who were followed for two years. The team found that regardless of gender and extent of advanced age, individuals with lower vitamin D levels at the start of the study were approximately twice as likely to exhibit significant cognitive decline over time.
In addition, low vitamin D levels at baseline also increased the risk of future cognitive impairment by two to three times, said the team led by Professor David Matchar at Duke-NUS Medical School.
The team noted that prospective studies from Western countries have suggested an association between lower vitamin D level and future cognitive decline in elderly people, however no prospective study has examined this association in Asia.
The new study is the first large-scale prospective study in Asia to study the association between vitamin D status and risk of cognitive decline and impairment in the Chinese elderly, said the team.
"Although this study was conducted on subjects from China, the results are applicable to regions in Asia where a large proportion of the elderly are ethnically Chinese, like Singapore," Matchar said.
The team analysed data from 1,202 subjects aged 60 years and over who took part in the Chinese Longitudinal Health Longevity Survey. Baseline vitamin D levels were measured at the start of the study, and cognitive abilities were assessed over two years.
Cognitive impairment was defined as a Mini-Mental State Examination (MMSE) test score under 18, while cognitive decline was defined as drop in score of three points or more from baseline level, said the team.
This first follow-up study of elderly people, including the oldest-old, in Asia shows that low vitamin D levels were associated with increased risk of subsequent cognitive decline and impairment.
Matchar and colleagues said the new findings reinforce the idea that vitamin D protects against neuron damage and loss, and means that calls for more intensive investigations into the effects of vitamin D supplements on cognitive decline should be acted on.
They noted that a better understanding of the mechanism by which vitamin D may protect neurons could help identify effective interventions to stem the rapidly increasing prevalence of cognitive decline observed in aging populations in Asia and around the world.
Last month research led by scientists at the Beijing Chaoyang Hospital and Capital Medical University, China, warned that the rapidly growing urban population in China may be at risk of severe deficiencies in vitamin D. The team said ‘targeted prevention’ and supplementation strategies are urgent for the growing urban Chinese population.
Source: The Journals of Gerontology Series A: Biological Sciences and Medical Sciences
Published online ahead of print, doi: 10.1093/gerona/glw128
“Vitamin D Levels and the Risk of Cognitive Decline in Chinese Elderly People: the Chinese Longitudinal Healthy Longevity Survey”
Authors: David B. Matchar, et al