Author Gabriel Garcia Marquez jotted down a profound yet simple belief shared by many: “Age isn't how old you are but how old you feel.” Unfortunately, biologists might describe age in a very different way. Aging, to a scientist, is a process of accumulating cell damage that impairs the function of bodily organs.
Now, researchers from the Max Planck Institute for Biology of Aging have discovered that this process is attributable not only to cellular damage that may occur over our lifetimes, but also to DNA damage inherited from our mothers.
Each cell in the body contains hundreds to thousands of mitochondria. These structures, which are located in the cytoplasm, the fluid surrounding the nucleus, convert the energy from food into a form that cells can use.
"The mitochondrion contains its own DNA, which changes more than the DNA in the nucleus, and this has a significant impact on the ageing process," Nils-Göran Larsson, researcher at the Max Planck Institute for Biology of Aging and lead author of the current study, explained in a press release. "Many mutations in the mitochondria gradually disable the cell's energy production." Along with these familiar mutations, it is also known that both normal and damaged DNA is passed down from generation to generation.
In the study, Larsson and his colleagues show that the aging process is attributable to maternally-inherited DNA as well as to damaged mitochondrial DNA accumulated over a person's lifetime. "If we inherit mDNA with mutations from our mother, we age more quickly," Larsson stated in the press release.
Having derived their data from experiments on mice, the researchers can only postulate that mild DNA damage transferred from the mother contributes to the overall aging process; whether or not it may be possible to correct the degree of inherited DNA damage — through, for example, lifestyle interventions — has not yet been determined. "Our findings can shed more light on the ageing process and prove that the mitochondria play a key part in ageing; they also show that it's important to reduce the number of mutations," Larsson stated in a press release.
And this is the next project for this group of researchers: an investigation into whether reducing the number of mutations can extend the lifespans of both mice and fruit flies. "The study also shows that low levels of mutated mDNA may have developmental effects and help to cause deformities of the brain," Lars Olson, co-author of the study, stated in a press release. Looking ahead, the researchers hope to broaden their examination of the aging process.
Really? Young at Heart?
Despite this new evidence, many people do not know and will never think of aging in such a clinical way. Aren’t we as young as we feel just like Marquez said? According to Dr. David Weiss from University of Zurich, research has shown that most older adults do feel significantly younger than their chronological age.
Accepted at face value, this is certainly a wonderful thing... but what underlies these youthful feelings?
Weiss posits many older adults may attempt to distance themselves from people their own age in order to maintain a positive view of themselves in the face of pervasive negative age stereotypes. In an experimental study published in Psychology and Aging, Weiss and his co-researcher ‘confronted’ groups of adults over the age of 65 with positive, neutral, and negative age-related information. After receiving negative age-related information, the older adults directed their gaze away from pictures of older adults and looked longer at middle-aged adults. In addition, the older adults began to perceive themselves as being more similar to middle-aged than to older adults.
“Feeling younger might allow older adults to maintain a positive view of themselves despite age-related losses,” the authors wrote.
The National Institute on Aging calculates approximately 40 million Americans age 65 or older were living in America in 2010. By 2030, this demographic is expected to swell to 72 million. In fact, the oldest of the old — people age 85 or older — constitute the fastest growing segment of the U.S. population; estimates place this group at slightly more than 19 million by 2050. Whether seen as a challenge or an opportunity (likely it will be both), these numbers compel not only older adults but the nation as a whole to redefine old age in such a way that this expanding population may remain both healthy and productive.
Sources: Ross JM, Stewart JB, Hagstrom E, et al. Germline mitochondrial DNA mutations aggravate ageing and can impair brain development. Nature. 2013.
Weiss D, Freund AM. Still young at heart: Negative age-related information motivates distancing from same-aged people. Psychology and Aging. 2012.