Tuesday August 11 2009
Face shape is a “clue to mental decline”, BBC News has reported. The website says that men with symmetrical faces are less likely to lose their memory and intelligence in later life. A new Scottish study has apparently found a link between facial symmetry and mental performance between the ages of 79 and 83 years.
This research analysed data on a small cross section of survivors from a study begun in 1921, and measured the symmetry of their faces at the age of 83. It demonstrated a link in men between their facial symmetry at 83 and changes in cognitive performance in the preceding four years, suggesting that those with less symmetrical faces also had demonstrable cognitive decline during that time. Overall, while this study may contribute to theories of ageing, its practical implications are difficult to appreciate. The study also has limitations, and its findings should be replicated in larger, prospective studies before firm conclusions can be drawn regarding the association between facial symmetry and cognitive function.
Where did the story come from?
Dr Lars Penke and colleagues from the University of Edinburgh and other Scottish institutions carried out this research. The study received direct or indirect support from the British Academy, the German Research Foundation and the UK Medical Research Council. The study was published in the peer-reviewed medical journal Evolution and Human Behaviour.
What kind of scientific study was this?
In this study researchers were looking for a “ready marker” that could indicate the progress of small, diverse changes and declines that reflect ageing in the body as a whole. One theory is that cognitive functions often decline simultaneously with physical functions, and a marker of when this is happening may offer some clues to the ageing process.
It is thought that there is no single cause responsible for this type of decline. Instead, environmental stresses, failure to adapt to these stress factors and problems with repair of cellular damage are all thought to contribute to general ageing.
The researchers wondered whether facial symmetry might be a marker of how the body is ageing overall, including cognitively. Facial symmetry has been shown to be a good indicator of developmental instability (the ability of an organism to protect itself from genetic or environmental challenges during development), and a number of studies have linked higher intelligence with lower fluctuating asymmetry (a greater level of symmetry).
Other studies have demonstrated this link more strongly in males than in females. Further research has also shown higher asymmetry in the elderly (those aged over 80) compared with people between the ages of newborn and 45 years.
Participants were surviving men and women born in 1921 who had taken part in both the Scottish Mental Survey in 1932 and a follow-up study between 1999 and 2001. The participants were an average of 79 years old during this follow-up study and were in good general health and living independently.
When they were 83 years old the participants underwent further cognitive testing. A total of 314 participants from the second study had four to six facial photographs taken while being asked to maintain a neutral expression. Some images were excluded as being unsuitable (facial hair obscuring features, no neutral expression, incorrect facial position).
Software was used to scan the pictures and assess the symmetry of the face based on 15 “facial landmarks” on each picture, such as the corners of the eyes, cheekbones and sides of the nostrils. From these measurements an index of facial asymmetry was calculated.
Cognitive tests had been performed in the original 1932 study, when members of the cohort were about 11 years old and again when they were around 79 years old. These results were converted into an IQ-like score. Further cognitive tests, including verbal fluency, nonverbal reasoning and memory tests, were administered when participants were 79 and 83 years old. Dementia and physical health and fitness were also assessed.
The researchers then compared facial asymmetry in this cohort with a sample of the general population (70 men and 72 women aged between 20 and 30 years). In the 216 elderly subjects with facial photographs available, researchers investigated the relationship between their index of facial asymmetry and changes in cognitive performance between different ages.
What were the results of the study?
In comparison with younger people from the general population, facial asymmetry was demonstrably higher and more variable in the elderly group of participants. The researchers found that facial asymmetry at 83 was not related to intelligence at 11, 79 or 83 years of age.
Facial asymmetry at age 83 was not related to cognitive changes between the ages of 11 and 79. However, male cognitive change between 79 and 83 years was related to facial symmetry, with men with lower facial asymmetry scores (more symmetrical faces) at 83 having less cognitive decline in the previous four years. This link was not evident in females.
Results did not change when the researchers excluded people with diabetes or took into account physical fitness and disease history.
What interpretations did the researchers draw from these results?
The researchers say that while prospective studies would be useful to explore confounding factors their results suggest that facial asymmetry is a possible marker (indicator) of decline in the integrity of both physical and cognitive body systems during ageing.
What does the NHS Knowledge Service make of this study?
This small study has demonstrated a link between facial symmetry and cognition in the elderly. This finding is not particularly surprising given that symmetry is a likely indicator of how successfully the body may have responded to potentially harmful genetic and environmental challenges to its development. On this basis, it could be considered a proxy measure of health.
As the researchers have reported, other studies have linked facial symmetry to higher intelligence in young people, although this finding was not replicated in this study.
This study has a number of limitations, some of which the researchers have highlighted:
- Facial asymmetry was only assessed at one point, when the participants were an average of 83 years old. The study cannot, therefore, explore causal relationships between facial asymmetry and cognition.
- Importantly, people who survive until 83, including all the participants in this study, are already a preselected, healthier group of adults. However, the researchers say that this would have meant that the links they were looking for were statistically harder to find and that, therefore, their study is likely to have underestimated the associations with facial asymmetry.
- All the effects found in this study were limited to men, so the absence of a link in women needs an explanation. The researchers offer some possibilities, but this difference between the sexes will need further exploration.
- Small strokes are a possible cause of cognitive decline and facial asymmetry. The fact that physical examinations were done at age 79 only raises the possibility that strokes or other physical illnesses affecting facial symmetry may have occurred between the ages of 79 and 83 years.
Overall, while this study may contribute to theories of ageing, its practical implications are difficult to appreciate. Given the limitations of the work, the findings should be replicated in larger, prospective studies before firm conclusions can be drawn about the association between facial symmetry and cognitive function.