April 3, 2012 — Visceral adiposity and a high body mass index (BMI) are associated with poor cognitive functioning in older adults, although only in those under age 70 years, a new study suggests.
The findings have important public health implications, especially as the population ages, said lead author, Dae Hyun Yoon, MD, PhD, associate professor, psychiatry, Seoul National University Hospital, South Korea.
“The prevention of obesity, particularly central obesity, might be important for the prevention of cognitive decline or dementia,” Dr. Yoon told Medscape Medical News.
The research was published online March 22 in Age and Ageing.
The study included 250 patients at least 60 years of age who had undergone abdominal computed tomography (CT) for screening of the digestive system. Researchers categorized visceral and subcutaneous adipose tissue areas on CT into sex-specific tertiles in patients younger than 70 years and those70 years and older. The highest tertile was a visceral adipose tissue area greater than 149.0 cm2 for men and greater than 123.7 cm2 for women.
Researchers assessed weight and height to determine BMI, with obesity defined as a BMI of 25 kg/m2 or greater. They also measured waist circumference.
Also considered were confounding risk factors, such as fasting glucose, total cholesterol, triglycerides, high-density lipoprotein cholesterol, and factors that could affect cognitive impairment (such as smoking and alcohol consumption).
Cognitive Testing
Participants completed the Korean version of the Mini-Mental State Examination (MMSE-KC). Poor cognitive performance was defined as an MMSE-KC total score at or below 1 standard deviation of the age, sex, and educational normative values of the Korean population.
Compared with nonobese participants under the age of 70, obese participants in that age group were generally older, were more likely to be male, and were more likely to have a higher prevalence of poor cognitive performance and hypertension.
After controlling for age, sex, education, hypertension, and diabetes, high BMI (odds ratio [OR], 2.61 [95% confidence interval (CI), 1.21 - 5.66]; P = .015) and being in the top tertile for visceral adipose tissue area (OR, 2.58 [95% CI, 1.001 - 6.62]; P = .045) were significantly associated with poor cognitive performance in those up to age 70 years.
Although a higher waist circumference (>90 cm for men and >80 cm for women) showed a tendency toward a positive association in a univariate analysis, this relation was not significant in the multivariate analysis.
“Waist circumference is influenced by subcutaneous as well as visceral adipose tissue, therefore, a direct measurement of visceral adipose tissue with the CT may have been more valid than anthropometric measurements like waist circumference,” explained Dr. Yoon.
Tertiles of the subcutaneous adipose tissue area were not related to poor cognitive performance. “Visceral adipose tissue is more metabolically active than subcutaneous adipose tissue and is thought to have a stronger influence on insulin resistance, among other things,” said Dr. Yoon. “It has long been considered as a pathogenic tissue compartment and this research shows a positive association between visceral adipose tissue area and low cognitive functioning.”
Older Elderly
There were no associations between any of the obesity measures — high BMI, waist circumference, visceral or subcutaneous adipose tissue area — and poor cognitive performance in the older age group.
“This finding suggests that the relation of visceral adiposity and low cognitive performance diminish with age,” said Dr. Yoon. “Aging is characterized by a lean body mass loss and adiposity measures like BMI are less useful in elderly persons.”
Dr. Yoon noted that a higher BMI is related to lower dementia risk in the oldest of old patients, and that it’s possible that persons with low BMI actually lose weight because of premorbid dementia.
“It’s also possible that a low BMI is the consequence of hyperinsulinemia, which precedes weight loss and is related to higher dementia risk,” he said.
The study was supported by the Konkuk University and Korea Healthcare technology R&D Project, Ministry for Health & Welfare. The authors have disclosed no relevant financial relationships.
Age Ageing. Published online March 22, 2012.