James E. Galvin, M.D., tests a patient's muscle strength in FAU's Comprehensive Center for Brain Health. Photo: Florida Atlantic University

The loss of muscle mass in older people, known as sarcopenia, has been linked to lower cognitive scores over a series of studies of seniors. High body-mass indices (BMIs) have shown lower cognition scores and mental processing speeds, and an increased incidence of Alzheimer’s and dementia.

But what happens when the two come together, when someone is "skinny-fat”? That is even more of a problem, according to a new study.

Sarcopenic obesity showed up as the biggest linkage in low cognition scores in a meta-analysis of studies between 2012 and 2015, as published by Florida Atlantic University researchers in the journal Clinical Interventions in Aging.

Their conclusion: whatever the cause, already the signs of "skinny-fat" can be used to hone in on possible cognitive impairment among some aged groups.

“Sarcopenia alone and in combination with sarcopenic obesity can be used in clinical practice as indicators of probably cognitive impairment,” the researchers said. “At-risk older adults may benefit from programs addressing loss of cognitive function by maintaining/improving strength and preventing obesity.”

The study involved 353 participants who were all over the age of 40, and who averaged 69.

All underweight cognitive testing such as the Montreal Cognitive Assessment, as well as strength tests such as grip strength or chair stands. Body composition, such as BMI and muscle mass and percentage of body fat, was also assessed.

The researchers found that sarcopenia was the biggest solitary linkage. The obese group alone were not statistically significant from the groups who were neither sarcopenic nor obese.

But when put together—“skinny fat"—the correlation was strongest of all. Working memory, mental flexibility, self-control and orientation were all decreased when the factors were identified in a single participant.

The obesity factor could be a cause, for example, through vascular or inflammatory mechanisms, or it could be a symptom of decreased cognition.

Similarly, sarcopenia has not been identified as a trigger or indicator of decreased mental capacity, according to the paper.

Further work needs to probe the connections, according to James Galvin, senior author, of FAU.

“Understanding the mechanisms through which this syndrome may affect cognition is important as it may inform efforts to prevent cognitive decline in later life by targeting at-risk groups with an imbalance between lean and fat mass,” Galvin said in a school statement. “They may benefit from program addressing loss of cognitive function by maintain and improving strength and preventing obesity.”