Relation of sleepiness to respiratory disturbance index - The Sleep Heart Health Study

Obstructive sleep apnea syndrome is a well recognized cause of excessive sl eepiness; however, the relation of sleepiness to mild sleep-disordered brea thing (SDB), which affects as much as half the adult population, is uncerta in. In order to explore this relation, we conducted a cross-sectional cohor t study of community-dwelling adults participating in the Sleep Heart Healt h Study, a longitudinal study of the cardiovascular consequences of SDB. Th e study sample comprises 886 men and 938 women, with a mean age of 65 (SD 1 1) yr. Sleepiness was quantified using the Epworth Sleepiness Scare (ESS), Steep-disordered breathing was quantified by the respiratory disturbance in dex (RDI), defined as the number of apneas plus hypopneas per hour of steep , measured during in-home polysomnography. When RDI was categorized into fo ur groups (< 5, 5 to < 15, 15 to < 30, greater than or equal to 30), a sign ificantly progressive increase in mean ESS score was seen across all four l evels of SDB, from 7.2 (4.3) in subjects with RDI < 5 to 9.3 (4.9) in subje cts with RDI greater than or equal to 30 (p < 0.001). There was no signific ant modification of this effect by age, sex, body mass index, or evidence o f chronic restriction of sleep time or periodic limb movement disorder. The percentage of subjects with excessive sleepiness, defined as an ESS score greater than or equal to 11, increased from 21% in subjects with RDI < 5 to 35% in those with RDI greater than or equal to 30 (p < 0.001). We conclude that SDB is associated with excess sleepiness in community-dwelling, middl e-aged and older adults, not limited to those with clinically apparent slee p apnea.