Dear Doctor: I heard that for senior citizens, being overweight and losing muscle can be bad for your memory. Is this really true? I'm worried because my husband has pretty much taken a seat on the couch since he retired two years ago. He hasn't gained any weight, but our sons have been saying that he's lost a step or two mentally. What can we do?
Dear Reader: The potential link between body fat, muscle mass and cognitive function in older adults has been a topic of discussion for many years. Dementia is a major cause of disability among the elderly, so it's an important area of study. In 2010, 30 million elderly adults worldwide had some type of dementia. That number is expected to more than triple to 106 million by 2050. Since cognitive decline is among the first observable symptoms of most types of dementia, detecting risk factors and identifying interventions is important to public health.
So far, studies into the connection between body fat, muscle mass and cognition in elderly adults have come up with conflicting results. The only hard-and-fast conclusion so far has been that the issue is complex and deserving of more study. Now we have the latest entry into the discussion, published in the journal Clinical Interventions in Aging earlier this year. A study found that the progressive loss of muscle mass among the elderly, as well as obesity, may be risk factors for cognitive decline that leads to dementia. This was found to be true when the conditions happened independently of one another but was more pronounced when they occurred together.
The progressive loss of muscle mass that takes place as we age is known as sarcopenia. And though it's associated with older adults, the process actually begins in our early 30s. Estimates put that loss at 3 to 5 percent of total muscle mass per decade. Combine this progressive loss of lean muscle mass with an increase in weight and body fat percentage and it's a condition known as sarcopenic obesity. (Sometimes it's referred to as "skinny fat.") Because muscle weighs more than fat, as muscle mass ebbs and fat percentages increase, the shift in body composition doesn't show up on the scale. Someone's weight can remain the same, but the ratio of lean muscle mass to total body fat can signal obesity.
In this most recent study, scientists analyzed the health data, including results of strength and cognitive testing, of 353 men and women with an average age of 69. It turned out that those with sarcopenic obesity fared the worst in cognitive testing. Those with just sarcopenia or just obesity fared only slightly better. Bottom line -- whether alone or together, loss of muscle mass and obesity were linked with impaired cognitive function. The reasons why aren't known, though inflammation and its attendant ills are high on the list of suspects.
As for your husband, persuading him to swap some couch time for weight-bearing and aerobic exercises is a good start. It will improve muscle strength, promote joint health and give his metabolism a boost. And if his mental lapses are apparent to the entire family, it's probably wise to have some cognitive testing done as well.
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