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The researchers of the study published their conclusions in the December issue of the British Medical Journal under the title “Perceived age as clinically useful biomarker of ageing: cohort study.”
The researchers wanted to find out if the perceived age of an individual (that is, what they look like to other people—do they look older or younger than their actual age) is important to overall mortality of the individual.
They used a population based twin cohort study from Denmark (called the Longitudinal Study of Aging Danish Twins, from 1995 to 2005) in which 387 Danish twins (774 total number) were used as the subjects.
The subjects were evaluated (assessed) with facial photographs by twenty geriatric nurses, ten young men who were student teachers (from the age of 22 to 37 years), and eleven elderly women between the ages of 70 and 87 years.
The assessors rated the perceived age of the twins by looking at pictures of the subjects’ faces.
And, they were unaware of the age of the twins. Each twin was evaluated on different days by the assessors.
The authors of this study are: Kaare Christensen, Mikael Thinggaard, Matt McGue, Helle Rexbye, and Jacob v B Hjelmborg (all from the Danish Twin Registry and Danish Aging Research Center, Institute of Public Health, University of Southern Denmark; Abraham Aviv (Center of Human Development and Aging, University of Medicine and Dentistry of New Jersey, New Jersey, U.S.A.); David Gunn and Frans van der Ouderaa (Unilever Discover, Colworth House, Sharnbrook, Bedfordshire, U.K.); and James W Vaupel (Max Planck Institute for Demographic Research, Rostock, Germany).
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The researchers measured the perceived age of the twins from photographs and physical and cognitive tests, along with the use of the length of leucocyte telomeres, which are a molecular biomarker of aging.
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A telomere that is of a shorter length usually signifies that a person will age faster.
These shorter-length telomeres have also been linked with larger numbers of diseases in individuals, when compared to longer-length telomeres in other individuals.
In the study, the twin that was perceived as being younger than the other sibling had longer telomeres.
As of January 2008, 675 of the subjects of the 1,826 total (37%) had died over a seven-year period.
The twin that was ranked as looking younger than the other twin tended to outlive their older-looking sibling.
The researchers found that the perceived age of each twin was significantly associated with survival and life span. Extraneous factors such as chronological age, sex, professional career, and the general environment did not change the results.
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Specifically, the researchers found, according to the abstract to their paper, “For all three groups of assessors, perceived age was significantly associated with survival, even after adjustment for chronological age, sex, and rearing environment. Perceived age was still significantly associated with survival after further adjustment for physical and cognitive functioning.”
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Specifically, “The likelihood that the older looking twin of the pair died first increased with increasing discordance in perceived age within the twin pair—that is, the bigger the difference in perceived age within the pair, the more likely that the older looking twin died first.” [Abstract]
“Twin analyses suggested that common genetic factors influence both perceived age and survival. Perceived age, controlled for chronological age and sex, also correlated significantly with physical and cognitive functioning as well as with leucocyte telomere length.”
The researchers concluded, “Perceived age—which is widely used by clinicians as a general indication of a patient’s health—is a robust biomarker of ageing that predicts survival among those aged 70 and correlates with important functional and molecular ageing phenotypes.”
For additional information, please read the BBC News article “People who look young for their age 'live longer'.”
