When studying some metabolic parameters in elderly people, it seems difficult to distinguish which ones are caused by aging per se or by age-related diseases. In particular, circulating IL-6 is known to increase with age but is it a relevant biomarker of aging since it is also elevated in metabolic diseases such as obesity or atherosclerosis. Then, is there a very specific biomarker of aging?
How can we characterize healthy elderly? For the recruitment of such cohort, do we exclude all kind of diseases or can we tolerate some?
Hello Delphine!
Good question.
From a very strict point of view, defining a healthy elderly is quite difficult, however, the most common situation is selecting those independent persons with no previous diagnosis of the event of interest, and run some screening tool in order to identify those who might be new diagnosis at the beginning of your study.
Most of studies include additional conditions in order to perform multivariate or multivariable analysis, which allow certain control of the situation you describe, however, often screening for periodontal diseases is ignored, and the inflammatory response promoted by periodontal diseases, may have a negative effect in certain metabolic diseases (such as diabetes), since it is a long time lasting disease and represent a lack of self care and the utilization of dental services.
Highlighting, look for independent persons, with no previous diagnosis of the event of interest out of health services facilities, with the less comorbidities as possible. In order of it, you may use the Frailty index developed by Rockwood and Mitnitski.
I hope this is useful.
Cheers.
There are two approaches to this problem, I think. Some biomarkers are considered to accumulate with age, such as advanced glycation endproducts in eye lens or skin collagen, aspartate racemization on collagen, and (to a limited extent) DNA damage, telomere shortening, immune cell population changes etc. . These can all be increased by disease, but there is a baseline increase in all of us. The second it to take a very large panel of biochemical markers that generally increase with age but also change in disease, and see which is the *least* 'old' in your subject. Thus (eg) if you measure glycation, IL-6, sarcopenia, skin elasticity and presbyopia, if the IL-6 levels are those you would expect in a 60-year-old, the glycation levels of a 100-year-old but the others all indicate a biochemical age of 40, then the subject's 'background' age level is 40 and the other higher values are due to specific disease (in this case probably undiagnosed diabetes). If this can be implemented effectively, then you do not have to screen out mild, background disease from your patient group. However you will find endless controversy over what the 'normal' or 'healthy' background increases or decreases in biochemical markers is.
There is a third approach, which is to ask whether your cohort is functionally healthy. There are plethora of functional tests of physical and mental capability. If your cohort can pass them to a level you would expect of a healthy N-year-old, then they are effectively healthy, whatever the biochemistry says.
Does this help?
William
Yes ! Thanks !
I think the last method is the best and this is what I will select.
Cheers
You may consider using Mitnitsky's Frailty Index for scoring the frailty state in the elderly. Here is the paper:
http://www.biomedcentral.com/1471-2318/14/25
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