SEATTLE, USA: It is known that the first 1,000 days after conception significantly affects a person’s life expectancy and disease susceptibility. While low birth weight, for example, has been established as a primary marker of early-life stress, the findings of a new study have suggested that lower-face asymmetries, assessed according to the asymmetry of occlusion, are a marker of environmental stress and cerebral lateralization during early development too.


In the study, researchers at the University of Washington assessed data on 6,654 U.S. adolescents collected between 1966 and 1970 as part of the National Health and Nutrition Examination Survey. More recent data were not used owing to a lack of current information on the prevalence of lower-face asymmetries in the U.S. population.

In total, an estimated 1 in 4 U.S. adolescents have lower-face asymmetries, the researchers concluded. Retrognathic asymmetries (17 percent), the most common lower-face asymmetry in the U.S. population, were found to fluctuate randomly between the left and right sides of the face. Such randomness indicates early-life stress, said lead author Prof. Philippe Hujoel, from the university’s School of Dentistry.

Hujoel emphasized that malaligned teeth, overbite and underbite have to be distinguished from asymmetric occlusion, as these conditions can be associated with asymmetric and symmetric occlusions, the last of which is largely a reflection of genetics, not environmental stress.

Further research is needed to identify whether lower-face asymmetries are predictive of chronic diseases in living populations in the same way that skull asymmetries have been associated with degenerative diseases in long-deceased populations.

The study, titled “Lower face asymmetry as a marker for developmental instability,” was published online on April 11 in the American Journal of Human Biology ahead of print