September 1, 2005
Low Levels of Blood Protein Tied to Muscle Decline
NEW YORK -- Older adults with relatively low levels of a particular blood protein may have a significant decline in muscle strength over time, a new study suggests.
The protein, called albumin, is known to fall to abnormal levels in certain diseases, including kidney and liver disease. In addition, high levels of other, inflammatory proteins in the blood can lower a person's albumin levels; chronic inflammation in the body is believed to contribute to a number of medical conditions, such as heart disease.
In the new study, older adults with relatively low albumin levels -- even within the range of normal -- had low levels of muscle strength, regardless of whether they had chronic conditions, such as heart disease and diabetes.
The subjects also showed a greater loss in muscle strength over time, according to findings published in the Journal of the American Geriatrics Society.
It's uncertain whether increasing an older person's albumin levels would improve his or her strength, according to the study authors, led by Dr. Bianca W. M. Schalk of VU University Medical Center in Amsterdam, the Netherlands.
Since low protein intake and general malnutrition can trigger a drop in albumin, future studies should look at the effects of special diet regimens on older adults' albumin levels and muscular strength, they recommend.
The question is an important one, the researchers point out, because slowing age-related muscle loss could make a difference in elderly adults' health and physical capabilities.
The study included more than 1,000 adults ages 65 to 88 whose changes in albumin levels and muscle strength were followed for at least 3 years. Schalk and her colleagues measured participants' blood levels of albumin and particular proteins involved in inflammation, and gathered information on their lifestyles and any existing medical conditions.
Grip strength tests were used to gauge their muscle strength.
The researchers found that nearly all of the study participants -- 99 percent --had normal albumin levels at the study's outset. Yet those with the lowest levels relative to their peers had poorer muscle strength. What's more, these men and women tended to lose more muscle strength over the next 3 to 6 years.
This relationship held true, though it weakened somewhat, when the researchers factored in participants' health conditions, levels of inflammatory proteins and lifestyle habits like smoking and exercise.
A missing element from the data, Schalk and her colleagues point out, was detailed information on diet. Poor nutrition, they note, through effects on protein synthesis in the body, could spur a decline in muscle strength.
However, the researchers add, since this is the first study to link blood albumin levels to age-related muscle decline, more studies are needed to confirm the relationship and to identify the underlying cause.
SOURCE: Journal of the American Geriatrics Society, August 2005.