Sarcopenia, which is the loss of muscle mass, tends to happen naturally with age. So, in older people with sarcopenia, excess body fat may not be readily visible. But hidden fat, paired with muscle mass loss later in life, could predict Alzheimer's risk, researchers warn.
A recent study — the results of which have been published in the journal Clinical Interventions in Aging — has found that sarcopenia and obesity (independently, but especially when occurring together) can heighten the risk of cognitive function impairments later in life.
The research was conducted by scientists at the Comprehensive Center for Brain Health at the Charles E. Schmidt College of Medicine of Florida Atlantic University in Boca Raton.
"Sarcopenia," explains senior study author Dr. James Galvin, "has been linked to global cognitive impairment and dysfunction in specific cognitive skills including memory, speed, and executive functions."
"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."
Dr. James Galvin
"They may benefit from programs addressing loss of cognitive function by maintaining and improving strength and preventing obesity," he adds.
Beware sarcopenic obesity
The scientists analyzed health-related data collected from 353 participants — aged 69, on average — all of whom registered to take part in community-based studies on aging and memory.
To establish whether or not there was a link between sarcopenic obesity — that is, the presence of excess body fat in conjunction with muscle mass loss — and cognitive decline, the team assessed participants' performance on tests evaluating cognitive function, including the Montreal Cognitive Assessment and
Also, the participants' muscle strength and mass were evaluated through grip strength tests and chair stands, and they also underwent body compositions assessments, which looked at muscle mass, body mass index (BMI), and the amount of body fat.
The researchers discovered that the participants with sarcopenic obesity had the poorest performance on cognition-related tests.
The next poorest performance on cognition tests was seen in people with sarcopenia alone, followed by participants who only had obesity.
Both when occurring independently and when occurring in concert, obesity and loss of muscle mass were linked with impaired working memory — which is the type of memory we use when making spontaneous decisions on a daily basis — as well as less mental flexibility, poorer orientation, and worse self-control.
Keep changes in body composition in check
The scientists explain that obesity could exacerbate the risk of cognitive decline through biological mechanisms that influence vascular health, metabolism, and inflammation.
Moreover, they warn that in people who already face impaired executive functioning, obesity might also impact energy resources through poor self-control that affects nutrition.
As for sarcopenia, the researchers note that it could influence brain mechanisms related to conflict resolution skills and selective attention.
Based on the study's findings, Dr. Galvin and his colleagues are particularly concerned that a mix of sarcopenia and excess body fat in older adults could become a serious public health issue, so they believe that any significant changes in body mass composition should be closely monitored to prevent negative health outcomes.
"Sarcopenia either alone or in the presence of obesity, can be used in clinical practice to estimate potential risk of cognitive impairment," notes study co-author Magdalena Tolea.
But such health issues can be kept under control, and the risks associated with them averted, she suggests.
"Testing grip strength by dynamometry can be easily administered within the time constraints of a clinic visit, and body mass index is usually collected as part of annual wellness visits," concludes Tolea.