Am. J. Respir. Crit. Care Med., Volume 164, Number 6, September 2001, 949-952

Genetic Factors in Self-reported Snoring and Excessive Daytime Sleepiness
A Twin Study

DORIT CARMELLI, DONALD L. BLIWISE, GARY E. SWAN, and TERRY REED

SRI International, Menlo Park, California; Emory University Medical Center, Atlanta, Georgia; and Indiana University, Indianapolis, Indiana

Subjects in this study included 1,560 intact male-male twin pairs (818 monozygotic [MZ], 742 dizygotic [DZ]) of mean age (± SD) 74.2 ± 2.8 yr. The Epworth Sleepiness Scale (ESS) was used to assess daytime sleepiness and standardized questionnaires assessed snoring. Multivariate genetic model fitting was used to estimate the contribution of genetic and nongenetic (environmental) influences to the variation and covariation of obesity with snoring and daytime sleepiness. In this sample, 26% were habitual snorers, 18% reported excessive daytime sleepiness (ESS  11), and 29% were obese (body mass index [BMI]  28). By using structural equation modeling, we estimated that genetic factors accounted for 64% of the variance in obesity, 40% of the variance in daytime sleepiness, and 23% of the variability in self-reports of snoring. We found a significant genetic correlation between obesity and snoring and between obesity and excessive daytime sleepiness (EDS), although for the most part the genetic variance in snoring and sleepiness was nonoverlapping with the genetic variance for obesity. We conclude from these data that self-reported symptoms of snoring and daytime sleepiness in older men have a genetic basis that is largely independent of genes associated with obesity.

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