A team of scientists from 3 Irish universities – St. James's
Hospital and Trinity College Dublin, both in Northern Ireland, and Nutrition
Innovation Centre for Food and Health at Ulster University – found that having
higher levels of belly fat in old age is associated with a decrease in
cognitive function.
Prevalence of Alzheimer’s and other forms of dementia is
growing with the rise in average age of population. Currently, an estimated 47
million people worldwide are affected by dementia. This number is expected to
rise to 75 million by 2030.
Scientists are trying to understand the risk factors
involved in dementia as it will help us with potential interventions to lower
the risk of this condition developing as we age. One such risk factor is
obesity.
Earlier studies have shown that overweight or obese adults
do not perform as well on tests of memory and visuospatial ability compared to
those who are a normal weight. However, researchers aren’t sure if this trend
continues into older age.
While previous studieshave looked into this matter, the results produced were
contradictory. Since each study involved different forms of cognitive test, it
is difficult to conduct a meta-analysis with the pooled results.
For this new study, the researchers set out to answer this
question more conclusively using a large-scale trial. [Read more High-fat diet damages brain, affecting learning and memory]
The scientists from the three universities used data from
the Trinity Ulster Department of Agriculture aging cohort study, which is a
cross-border collaborative research project gathering data from thousands of
adults over the age of 60 in Northern Ireland and Ireland.
Each of the 5,186 participants was assessed using a number of
cognitive tests.
The team found that a higher waist to hip ratio was linked
with reduced cognitive function. This could be due to an increased secretion of
inflammatory markers by belly fat, which in previous studies had been linked
with a higher risk of cognitive impairment.
On the contrary, bodymass index (BMI) measurements did not show the same trend; in fact,
higher BMI was found to protect cognitive function. Researchers believe this is
because BMI is a crude measure of body fat and cannot differentiate between fat
and fat-free mass (muscle); it only takes into account weight and height.
How cognition is
influenced by belly fat?
Researchers believe that belly fat's impact on cognition
might be due to high secretion of inflammatory markers – particularly
C-reactive protein. This chemical is produced when fat cells send out signals.
Increased levels of this have previously been linked to cognitive decline.
It should also be noted that according to studies, levels of
inflammatory markers in the blood increases in the lead-in to dementia, before
symptoms appear.
Hemoglobin A1C
(HbA1C) is another molecule that seemed crucial. When during their analysis,
the researchers controlled for levels of HbA1C, the significant effect of belly
fat on cognition disappeared.
The prevalence of obesity and dementia are putting enormous
burdens on the society. Studies like this are crucial because by reducing
obesity we may be able to curtail the prevalence of dementia.
The findings are published in the British Journal of Nutrition.
