Study: Lack of vitamin D raises risks of cognitive impairment
RESEARCHERS at Duke-NUS Medical School have found that low vitamin D levels predict cognitive impairment in elderly Chinese people.
Cognitive abilities include memory and thinking skills.
Professor David Matchar, director of the Health Services and Systems Research Programme at Duke-NUS, led a team of six others in a two-year study of 1,202 subjects with a mean age of 80 from eight provinces in China.
They split the participants into four groups of varying vitamin D3 levels measured at the start of the study. Vitamin D3 is the most common form of vitamin D circulating in the bloodstream. Participants were selected based on age and had no signs of cognitive impairment.
During the two years, they were tested on their level of cognitive function using a Mandarin version of a "mini-mental status examination".
It allocated up to 30 points to each participant based on performance.
A decrease of three or more points suggested a decline in cognitive function.
Falling below the threshold of 18 at the end of two years indicated impairment.
The team found that the group with the lowest levels of vitamin D3 was three times more likely to develop cognitive impairment than the group with the highest levels.
The mean level of vitamin D3 in the lowest group was 25.1 nanomoles per litre (nmol/L) while that of the highest group was 66.4nmol/L.
Normal levels should be between 50 and 70nmol/L, said Prof Matchar.
It was the first large-scale longitudinal study on an Asian population with regard to vitamin D levels and cognitive impairment.
Previous studies on Western populations in Europe and North America showed similar results, he added.
"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," he noted.
The study is especially relevant to Singapore, with a rapidly ageing population and an estimated 40,000 people with cognitive impairments, he said.
Common causes of cognitive impairment in Singapore include Alzheimer's disease and vascular dementia.
The study shows that low vitamin D levels increase the risk of such diseases.
Prof Matchar recommended that people take daily supplements or spend time in the sun when the sun is straight up in the sky, providing maximum UVB light, which promotes the formation of vitamin D in the body using cholesterol.