IADR Abstract Archives
Heritability of the Airway Determined by Twin Study Data
Objectives: The objective of this study was to use lateral cephalograms from monozygotic (MZ) and dizygotic (DZ) twin pairs to estimate the heritability of various cephalometric and airway measurements at pre- and post-pubertal time points.
Methods: Deidentified lateral cephalograms were obtained from the Forsyth Twin Study (1959-1976) data set. Lateral cephalograms were traced using Dolphin Imaging software for 35 MZ and 35 same-sex DZ twin pairs at T1 (age 8 +/- 1 year) and T2 (age 17 +/- 1 year). Classic cephalometric measurements and airway measurements determined on lateral cephalograms were obtained from the tracings. Correlation coefficients and subsequent heritability estimates were calculated for each cephalometric and airway measurement for MZ twins at T1, MZ twins at T2, DZ twins at T1, and DZ twins at T2. Falconer’s Formula was used to calculate heritability estimates.
Results: Heritability estimates typically range from 0 to 1 with lower numbers indicating low trait heritability (low genetic influence/high environmental influence) and higher numbers indicating high trait heritability (high genetic influence/low environmental influence). Posterior Airway Space (PAS), Middle Airway Space (MAS), and Superior Airway Space (SAS) share similar trends with high heritability estimates at T1 (0.80, 0.66, and 0.95, respectively) and low heritability estimates at T2 (0.02, 0.30, and 0.46, respectively). Conversely, Co-Gn, SN-MP, and SNB share similar trends with low heritability estimates at T1 (0.30, 0.65, and 0.46, respectively) and high heritability estimates at T2 (0.78, 0.92, and 0.85, respectively). These results are based on preliminary data.
Conclusions: Airway dimensions (PAS, MAS, and SAS) are highly heritable at early ages, but much of the genetic effect is overtaken by environmental factors after puberty. On the other hand, some skeletal factors such as Co-Gn, SN-MP and SNB have low heritability early and high heritability late suggesting a greater genetic influence after puberty.
Methods: Deidentified lateral cephalograms were obtained from the Forsyth Twin Study (1959-1976) data set. Lateral cephalograms were traced using Dolphin Imaging software for 35 MZ and 35 same-sex DZ twin pairs at T1 (age 8 +/- 1 year) and T2 (age 17 +/- 1 year). Classic cephalometric measurements and airway measurements determined on lateral cephalograms were obtained from the tracings. Correlation coefficients and subsequent heritability estimates were calculated for each cephalometric and airway measurement for MZ twins at T1, MZ twins at T2, DZ twins at T1, and DZ twins at T2. Falconer’s Formula was used to calculate heritability estimates.
Results: Heritability estimates typically range from 0 to 1 with lower numbers indicating low trait heritability (low genetic influence/high environmental influence) and higher numbers indicating high trait heritability (high genetic influence/low environmental influence). Posterior Airway Space (PAS), Middle Airway Space (MAS), and Superior Airway Space (SAS) share similar trends with high heritability estimates at T1 (0.80, 0.66, and 0.95, respectively) and low heritability estimates at T2 (0.02, 0.30, and 0.46, respectively). Conversely, Co-Gn, SN-MP, and SNB share similar trends with low heritability estimates at T1 (0.30, 0.65, and 0.46, respectively) and high heritability estimates at T2 (0.78, 0.92, and 0.85, respectively). These results are based on preliminary data.
Conclusions: Airway dimensions (PAS, MAS, and SAS) are highly heritable at early ages, but much of the genetic effect is overtaken by environmental factors after puberty. On the other hand, some skeletal factors such as Co-Gn, SN-MP and SNB have low heritability early and high heritability late suggesting a greater genetic influence after puberty.