The British study
involving 3700 men and women, found that lower levels of high-density
lipoprotein, or HDL cholesterol was linked to declining memory by the
age of 60. These memory declines are believed to precede the
development of dementias such as Alzheimer's disease.
Experts have
estimated that more people will develop Alzheimer's disease worldwide
over the coming decades as the populations of older people in many
countries have continued to increase significantly. As more
individuals are growing older, scientists are trying to identify risk
factors that may precede the onset of dementia in an effort to find
ways to prevent or postpone its occurrence. Archana Sing-Manoux of the
French National Institute for Health and Research and the University
College of London, who led the study, stated "Considering the way the
population is aging-the 65 plus age group being the fastest-growing
age group-we're facing a dementia time bomb." She hoped to focus
attention on the possible benefits of higher levels of HDL cholesterol
and protection against the loss of memory.
Researchers gave a
simple memory test that collected results when people were on the
average of 55 years old, and then at a later time when they were at an
average age of 60 years old.
In memory tests,
individuals had 20 words read to them and then were asked to write
down as many words as they could remember in two minutes. At the age
of 55, participants with low HDL cholesterol levels had a 25 7% higher
risk of memory loss compared to other individuals with higher levels
of HDL. At the age of 60, individuals in the same low HDL category
had a 53% higher risk of memory loss compared to study groups who had
high levels of HDL.
The study did not
track subsequently if individuals in these groups went on to develop
Alzheimer's or some other form of dementia.
Cholesterol is the
fatty substance that is found in many foods and is also made naturally
by the body. High levels of HDL cholesterol have been found to reduce
the risk of heart attacks. The good or HDL cholesterol takes excess
cholesterol back to the liver as opposed to the low density
lipoprotein (LDL) cholesterol, which is believed to build up in artery
walls making them hard and narrow and is considered to be the "bad"
cholesterol. The study did not find total cholesterol and
triglycerides, which is another type of fat found in the blood to have
any association with memory decline. Although the study did not look
at the reason behind the protective effects of HDL cholesterol,
Singh-Manoux said that one possible explanation may be that it has a
tendency to ward off the formation of beta-amyloid plaques in the
brain that are believed to be markers of Alzheimer's disease.
Previous studies
have also identified additional risk factors associated with dementia
and Alzheimer's disease. U.S. researchers found in March that having
a big belly in middle-age also appears to greatly increase an
individual's risk of developing Alzheimer's or other forms of dementia
decades later.
A recent European
study found that middle-aged people with lower levels of HDL
cholesterol may be at a higher risk for memory decline, which could be
a precursor to Alzheimer's disease or other forms of dementia.