THE FAMILIAL AGGREGATION OF OBSTRUCTIVE SLEEP-APNEA

An inherited basis for sleep-disordered breathing (SDB) has been sugge sted by reports of families with multiple affected members and by a pr evious study of the familial aggregation of symptoms of SDB. In this s tudy, we quantify and characterize the aggregation of SDB and assess t he degree to which familiar similarities may be independent of obesity . This was a genetic-epidemiologic study that assessed the distributio n of SDB in families identified through a proband with diagnosed sleep apnea and among families in the same community with no relative with known sleep apnea. SDB was assessed with overnight in-home monitoring of airflow, oxygen saturation, chest wall impedance, heart rate, and b ody movement. Standardized questionnaires were used to assess symptoms , and weight, height, and neck circumference were measured directly. I ntergenerational and intragenerational correlation coefficients and pa irwise odds ratios (ORs) were calculated with adjustment for proband s ampling. In toto, 561 members of 91 families were studied: (1) 47 subj ects with laboratory-confirmed SDB (index probands), (2) 44 community control subjects, and (3) the spouses and relatives of 1 and 2. Of all 91 families, 32 (35%) had two or more members with SDB, 30 (33%) had one affected member, and 29 had no affected members. SDB was more prev alent in the relatives of index probands (21%) than among neighborhood control subjects (12%) (p = 0.02). After adjusting for age, sex, race , and obesity, the odds of SDB, defined on the basis of age-specific t hreshold values for the respiratory disturbance index (RDI), was 1.3 g reater in subjects with one affected relative, and 2.3 greater in subj ects with three affected members when compared with subjects without a ffected family members. Intergenerational and intragenerational coeffi cients, describing the similarities in RDI levels among family members , were each 0.21 (p < 0.005), and they were not reduced significantly with adjustment for obesity. These results suggest that SDB significan tly aggregates within families and that risk increases progressively w ith increasing numbers of affected relatives. The familial aggregation of SDB is not explained entirely by familial similarities in body mas s index (BMI) or neck circumference, suggesting the importance of othe r familiar factors in increasing susceptibility to the disorder.