Correlations in Dysfunction Abound in Aging

Aging is a global phenomenon, the spiraling consequences of underlying damage that accumulate in every organ and biological system of the body concurrently. Becoming damaged is a matter of wear and tear; it is a side-effect of the operation of metabolism. Over most of life and for most people at a given age environmental factors make up the largest difference in the pace of aging from individual to individual: who takes care of their health; who becomes fat; who fails to exercise; and so forth. When compared with the differences caused by advances in medical technology, this is small change, however - not something to spend too much time worrying about. Live a sensibly healthy life, and where you do have time and energy for doing more, focus on helping to create new forms of medicine that can break us out of the old traditional length of life, adding decades to healthy life span while preventing and curing the diseases of old age.

Given that aging is a global process, it is comparatively easy to identify correlations between specific forms of dysfunction. If you are further along in failing health in one way, then the odds are very good that the same is true of all every other measure of aging as well. Chronic diseases of aging, and the general loss of function and health that precede them, tend to come in clusters. Everything is failing at once, and then in the end it is just a roll of the dice as to which fatal event happens first. One day people will look back on the ugly realities of aging as we look back on the ugly realities of infectious disease in past centuries. How did they bear it? Why was there any acceptance at all of such widespread death and suffering? Why didn't they try harder to build the medical and other technologies needed to escape that state of affairs?

While you ponder that, here are a few recent examples of correlations in aging and longevity:

Association of exceptional parental longevity and physical function in aging

Offspring of parents with exceptional longevity (OPEL), who are more likely to carry longevity-associated genotypes, may age more successfully than offspring of parents with usual survival (OPUS). Maintenance of physical function is a key attribute of successful aging. While many genetic and non-genetic factors interact to determine physical phenotype in aging, examination of the contribution of exceptional parental longevity to physical function in aging is limited.

The LonGenity study recruited a relatively genetically homogenous cohort of Ashkenazi Jewish (AJ) adults age 65 and older, who were defined as either OPEL (having at least one parent who lived to age 95 or older) or OPUS (neither parent survived to age 95). Subjective and objective measures of physical function were compared between the two groups, accounting for potential confounders. Of the 893 LonGenity subjects, 365 were OPEL and 528 were OPUS. OPEL had better objective and subjective measures of physical function than OPUS, especially on unipedal stance and gait speed. Results support the protective role of exceptional parental longevity in preventing decline in physical function, possibly via genetic mechanisms that should be further explored.

Slow walking speed and memory complaints can predict dementia

"As a young researcher, I examined hundreds of patients and noticed that if an older person was walking slowly, there was a good chance that his cognitive tests were also abnormal. This gave me the idea that perhaps we could use this simple clinical sign - how fast someone walks - to predict who would develop dementia."

[Researchers] reported on the prevalence of motoric cognitive risk syndrome (MCR) among 26,802 adults without dementia or disability aged 60 years and older enrolled in 22 studies in 17 countries. A significant number of adults - 9.7 percent - met the criteria for MCR (i.e., abnormally slow gait and cognitive complaints). While the syndrome was equally common in men and women, highly educated people were less likely to test positive for MCR compared with less-educated individuals. A slow gait is a walking speed slower than about one meter per second, which is about 2.2 miles per hour (m.p.h.). Less than 0.6 meters per second (or 1.3 m.p.h.) is "clearly abnormal."

To test whether MCR predicts future dementia, the researchers focused on four of the 22 studies that tested a total of 4,812 people for MCR and then evaluated them annually over an average follow-up period of 12 years to see which ones developed dementia. Those who met the criteria for MCR were nearly twice as likely to develop dementia over the following 12 years compared with people who did not.

Association of Hearing Impairment and Mortality in Older Adults

Hearing impairment (HI) is highly prevalent in older adults and is associated with social isolation, depression, and risk of dementia. Whether HI is associated with broader downstream outcomes is unclear. We undertook this study to determine whether audiometric HI is associated with mortality in older adults.

Prospective observational data from 1,958 adults ≥70 years of age from the Health, Aging, and Body Composition Study were analyzed using Cox proportional hazards regression. Participants were followed for 8 years after audiometric examination. Mortality was adjudicated by obtaining death certificates. Of the 1,146 participants with HI, 492 (42.9%) died compared with 255 (31.4%) of the 812 with normal hearing. After adjustment for demographics and cardiovascular risk factors, HI was associated with a 20% increased mortality risk compared with normal hearing. Confirmatory analyses treating HI as a continuous predictor yielded similar results, demonstrating a nonlinear increase in mortality risk with increasing HI.


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