Obstructive Sleep Apnea Hypopnea 381
Obstructive sleep apnea hypopnea has a strong  genetic basis, as evidenced by the sig-
nificant familial aggregation of the apnea hy popnea index. The prevalence of obstructive
sleep apnea hypopnea is approximately twice as high among the first-degree relatives of
probands with obstructive sleep apnea hypopn ea as compared with members of control
families. One-third of the variance in the apnea hypopnea index is explained by shared fa-
milial factors. Although genetic markers with diagnostic or prognostic value are not yet
available for use, eliciting a family history of obstructive sleep apnea hypopnea should in-
crease the clinical suspicion for the disorder.
Culture-Related Diagnostic Issues
There is a potential for sleepiness and fatigue to  be reported differently across cultures. In
some groups, snoring may be considered a si gn of health and thus may not trigger con-
cerns. Individuals of Asian ancestry may be at increased risk for obstructive sleep apnea
hypopnea despite relatively low BMI, possibly reflecting the influence of craniofacial risk
factors that narrow the nasopharynx.
Gender-Related Issues 
Females may more commonly report fatigue rather than sleepiness and may underreport
snoring. 
Diagnostic Markers
Polysomnography provides quan titative data on frequency of sleep-related respiratory
disturbances and associated changes in oxygen saturation and sleep continuity. Polysom-
nographic findings in children differ from th ose in adults in that children demonstrate
labored breathing, partial obst ructive hypoventilation with cyclical desaturations, hyper-
capnia and paradoxical movements. Apnea hy popnea index levels as low as 2 are used to
define thresholds of abnormality in children.