BACKGROUND:

The contribution of genetic factors to sleep disorders has been demonstrated in twin and family studies, and further understanding of the genetic underpinning of sleep disorders is considered an important area of research. Many of the suggested risk factors for sleep apnea (e.g.,craniofacial morphology, obesity) have genetic determinants. However, a formal genetic analysis of these anatomical risk factors with sleep-recorded physiological measurements has not so far been conducted.

DESIGN NARRATIVE:

The investigators recruited a subsample of pairs from the NAS-NRC World War II Twin Registry in which at least one of the twin brothers reported sleep apnea symptoms and a subsample of control pairs in which both twins reported no symptoms. They monitoring the subgroup of twin pairs with overnight sleep recording. They also collected anthropometric measurements of weight, height, neck circumference, and craniofacial morphology and blood samples for determination of zygosity and DNA extraction for future molecular studies.

The twin design is most powerful for estimating the genetic and/or environmental overlap between physiological measurements such as sleep-recorded disordered breathing, obesity, and craniofacial morphology. The investigators chose to focus on an elderly male twin sample for which a wealth of data relevant to this study had been previously collected. Twin pair concordance or discordance for monitored sleep-disordered breathing allowed the full characterization of genetic/familial and individual environmental factors associated with the expression and severity of this condition.