Measures of cognitive function in persons with varying degrees of sleep-disordered breathing: the Sleep Heart Health Study LORIL.BOLAND 1 ,EYALSHAHAR 1 ,CONRADIBER 2 , DAVIDS.KNOPMAN 3 ,TRACYF.KUO 4 andF.JAVIERNIETO 5 FortheSleepHeartHealthStudy(SHHS)Investigators 1 Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis, MN, USA, 2 Department of Medicine, University of Minnesota, Minneapolis, MN, USA, 3 Department of Neurology, Mayo Clinic, Rochester, MN, USA, 4 Department of Psychiatry and Behavioral Sciences, Stanford University, School of Medicine, Stanford, CA, USA and 5 Department of Epidemiology, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD, USA Accepted in revised form 27 June 2002; received 8 May 2002 SUMMARY Epidemiologic literature suggests that persons with clinically diagnosed sleep apnoea frequently have impaired cognitive function, but whether milder degrees of sleep- disordered breathing (SDB) are associated with cognitive dysfunction in the general population is largely unknown. Approximately 1700 subjects free of clinically diagnosed SDB underwent at-home polysomnography (PSG) as part of the Sleep Heart Health Study (SHHS) and completed three cognitive function tests within 1–2 years of their PSG: the Delayed Word Recall Test (DWR), the WAIS-R Digit Symbol Subtest (DSS), and the Word Fluency test (WF). A respiratory disturbance index (RDI) was calculated as the number of apnoeas and hypopnoeas per hour of sleep. After adjustment for age, education, occupation, field centre, diabetes, hyper- tension, body-mass index, use of CNS medications, and alcohol drinking status, there wasnoconsistentassociationbetweentheRDIandanyofthethreecognitivefunction measures. There was no evidence of a dose–response relation between the RDI and cognitive function scores and the adjusted mean scores by quartiles of RDI never differedfromoneanotherbymorethan5%foranyofthetests.Inthissampleoffree- living individuals with mostly mild to moderate levels of SDB, the degree of SDB appeared to be unrelated to three measures of cognitive performance. keywords cognition, hypoxaemia, neuropsychology, sleep-disordered breathing INTRODUCTION Clinical studies have shown that persons with diagnosed sleep apnoea frequently exhibit some degree of cognitive impair- ment (Be´dard et al. 1991; Bliwise 1989; Findley et al. 1986; Flemons and Tsai 1997; Greenberg et al. 1987; Kales et al. 1985; Nae¨gele´ et al. 1995), and that cognitive functioning among these individuals often improves after treatment with continuous positive airway pressure (CPAP) (Borak et al. 1996; Feuerstein et al. 1997; Valencia-Flores et al. 1996). However, sleep apnoea is one extreme of a continuum of sleep-disordered breathing (SDB) in the general population (Young et al. 1993), and less is known about the neurological sequelae of milder degrees of SDB. Cognitive function measures were available for approximately 1700 men and women free of clinically diagnosed sleep apnoea who under- went at-home polysomnography (PSG) as part of the Sleep Heart Health Study (SHHS). This report examines the relation between cognitive functioning and indicators of SDB in a sample of free-living individuals with primarily mild to moderate levels of SDB. Correspondence: Eyal Shahar, MD, MPH, Division of Epidemiology, University of Minnesota, 1300 South Second Street, Suite 300, Minneapolis, MN 55454, USA. Tel.: (612) 624–8231; fax: (612) 624 0315; e-mail: shahar@epi.umn.edu J. Sleep Res. (2002) 11, 265–272 Ó 2002 European Sleep Research Society 265