Obesity in later life linked to decreased mental faculties

By Dr. Ananya Mandal, MDMar 25 2012

A new Korean study has found that older adults who a high body mass index (BMI) may have less brain power.

The study found said out of 250 test subjects involving people over 59 years old, people between 60 and 70 who had the highest BMIs also had the lowest cognitive function. There was also a connection between visceral fat -- otherwise known as the belly fat around the torso - and poor mental abilities. The study, which was published in the British journal Age and Aging, measured the subjects fat-related measures including BMI, waist circumference and the amount of visceral - which could be close to organs - and subcutaneous -under the skin - fat using a abdominal CT scan. Cognitive ability was determined by a test called a Mini-Mental State Examination.

“Our findings have important public health implications. The prevention of obesity, particularly central obesity, might be important for the prevention of cognitive decline or dementia,” study author Dae Hyun Yoon, a researcher at Seoul National University Hospital Healthcare System in South Korea told BBC News.

Researchers add that there was no correlation found in people older than 70. In fact a higher BMI led to lower dementia risk with for folks in that age range, but it was possible that the subjects with lower BMIs lost all their weight by that age because of dementia or other medical conditions, Yoon told ABC News.

According to the National Institute of Health (NIH), dementia is a group of symptoms that reflect a loss of brain function including memory, thinking, language, judgment and behavior. It is rare for anyone under 60 to have the disease. The most common cause of progressive dementia is Alzheimer's disease, according to the Mayo Clinic. The Alzheimer's Association said affects one in eight older Americans each year or 5.4 million people. It is the sixth-leading cause of death in the U.S.

Obesity has been linked in several previous studies to lower cognitive function, including an NIH study that said combined presence of midlife hypertension and a high BMI and waist-to-hip ratio led to a decline in cognitive skills in over 1,800 men and women aged 40 to 69. Obesity contributes to 7 percent of Alzheimer's cases, according to a recent study.

The Alzheimer's Society said the research added to evidence that excess body fat can affect brain function. Lifestyle changes can help make a difference, it said. A spokesperson from the UK Alzheimer's Society said, “We have all heard how a high BMI is bad for our heart but this research suggests it could also be bad for the head. Although we don't know whether the people in this study went on to develop dementia, these findings add to the evidence that excess body fat could impact on brain function. One in three people over 65 will die with dementia but there are things people can do to reduce their risk. Eating a balanced diet, maintaining a healthy weight, exercising regularly and getting your blood pressure and cholesterol checked can all make a difference.”

In a related study it was found that women who are overweight before pregnancy predispose their children to developing cardio-metabolic syndrome as young adults.

Researchers from Israel and the United States found that greater maternal pre-pregnancy body mass index (BMI)—independent of weight gained during pregnancy—is significantly associated with higher offspring BMI, waist circumference, systolic and diastolic blood pressures, and insulin and triglyceride levels and with lower levels of high-density lipoprotein cholesterol at age 32. Further, gestational weight gain—independent of maternal pre-pregnancy BMI—was positively associated with offspring adiposity at the same age, suggesting that offspring adiposity was the main driver of the associations.

Using a birth cohort of 1,400 Jerusalem residents born between 1974 and 1976 and participating in the Jerusalem Perinatal Family Follow-Up Study, researchers analyzed the long-term effects of maternal pre-pregnancy BMI and gestational weight gain on other related cardio-metabolic factors (ie, glucose, insulin, lipids, and lipoproteins) measured in early adult offspring.

In their study, published in Circulation, the authors write that the most likely mechanisms for the associations are not only shared genetic and environmental factors but intrauterine factors and that “epigenetic processes linking environmental and genetic factors” are involved in transmitting information from the uterus to offspring later in life. The authors note that at the time the cohort was established, obesity rates were not nearly what they are today.