Monday December 14 2009
The study did not take lifestyle factors into account
“People whose faces belie their real age also live longer, enjoy better health and are less likely to get dementia,” The Guardian reported. It said that research suggests that perceived age is a better predictor than actual age for physical and mental health in the elderly.
The study followed a large group of twins over 70 years of age and asked people to assess their age from photos. The researchers looked for associations between actual age and perceived age on their ability to do physical and cognitive tasks and their survival rate over a seven-year follow-up period.
Although the researchers found that perceived age seemed to be associated with physical and cognitive markers and survival, this link was not that much more informative than actual age. A noteworthy flaw of this study is that it did not take into account lifestyle factors such as smoking and diet.
Where did the story come from?
This research was carried out by Professor Kaare Christensen and colleagues at the Danish Aging Research Centre at the University of Southern Denmark. It was funded by Unilever and the National Institute of Health (US). The study was published in the peer-reviewed medical journal The British Medical Journal.
The press tended to focus on this research giving evidence for lifestyle choices that may age the skin, thereby increasing your risk of ill health. However, the research did not look at the participants’ lifestyle or their medical history and so it is not possible to say what caused participants’ who looked older to have poorer scores on physical and cognitive tests. There is no evidence for a link between increased perceived age and dementia.
What kind of research was this?
This cohort study followed 1,826 twins in Denmark for seven years. The researchers says, “When assessing health, physicians traditionally compare perceived and chronological age, and for adult patients the expression ‘looking old for your age’ is an indicator of poor health”. They wanted to test whether perceived age was a better indicator of health in the elderly than actual age.
What did the research involve?
The study followed 1,826 same sex twins in Denmark who were over 70 years old. In the majority of cases, both twins participated. However, participants whose co-twin did not want to participate, or who had died, were also included.
The researchers took photographs of 840 male and 946 female twins. Of these, there were 175 identical twins and 212 non-identical twins. The participants’ ages were assessed by three separate groups of judges using the photographs. The judges were 20 female geriatric nurses aged 25 to 46, 10 male student teachers aged 22 to 37 and 11 older women aged 70 to 87.
The researchers then assessed the participants’ physical strength with a series of tasks such as walking up two flights of stairs and their hand grip strength. Their mental health was assessed using the mini-mental state examination, a standard test of cognition that can detect age-related changes in brain function.
Using blood samples provided by some of the participants, the researchers extracted DNA to examine the telomeres. Telomeres are regions of DNA at the end of a chromosome that protect the chromosome as cells divide throughout life. The length of the telomeres can give researchers an indication of how many divisions a cell has gone through and how many more divisions the cell can go through.
At the end of a seven-year follow up period, the number of participants who had died was counted and the risk of mortality and that person's perceived age compared.
What were the basic results?
Early on in the study, the researchers found that the guesses of the participants’ ages tended to be same across the three groups of judges. Therefore, for the remainder of the study, the researchers decided to use 10 individuals in the nurses group to make the age assessments. On average, the perceived age was within a year of the actual age.
The perceived age data agreed with other markers of age such as physical strength, cognitive ability and telomere length.
The researchers found that in non-identical twins there was an increased chance that the older looking twin died first, and that the larger the difference between the perceived age and the actual age, the greater the chance the older looking twin would die first. They did not see the same pattern with the identical twins.
How did the researchers interpret the results?
The researchers concluded that perceived age predicted survival and the physical and cognitive changes associated with age. They found that an increase in perceived age was associated with a decreased risk of survival when they compared non-identical twins with each other, but not when identical twins were compared to each other. The researchers conclude that this suggests that there may be genetic factors influencing both survival and perceived age.
Specific health hazards, such as smoking, sun exposure or low socioeconomic status may affect how old a person looks. This research investigated whether perceived age is a better marker of age-related changes and survival than actual age. Although the researchers showed there was some association between an increased perceived age over actual age and other physical and cognitive effects of old age, there are a few limitations to this study.
- The researchers highlight that nearly all the cohort members were white, and white assessors were used. Cross-cultural or ethnic rating might be more difficult than rating within a culture.
- The overall average difference in perceived age and actual age was small, therefore the increased correlation may not be that much more useful than actual age to predict health.
- In identical twins, no association was found between a greater difference in perceived age to actual age and increased mortality. This suggests that there may be other genetic factors that affect both how old you look and how long you live for.
The study did not look at the past medical records or the lifestyle of the participants. Therefore, what actually caused the older looking twins to have decreased survival cannot be determined from this study.