Cognitive function and sleep related breathing disorders in a healthy elderly population: The synapse study

Abstract

Study Objectives: Sleep related breathing disorders (SRBD) are risk factors for cognitive dysfunction in middle-aged subjects, but this association has not been observed in the elderly. We assess the impact of SRBD on cognitive performance in a large cohort of healthy elderly subjects. Design: Cross-sectional study examining the association between subjective memory test, neuropsychological battery testing and SRBD in the elderly. Setting: Community-based sample in home and research clinical settings. Participants: 827 subjects, 58.5% women, aged 68 y at study entry, participated in the study. All were free of previously diagnosed SRBD, coronary heart disease, and neurological disorders, including stroke and dementia. Clinical interview, neurological assessment, polygraphy, and extensive cognitive testing were conducted for all participants. Intervention: N/A Measurement and Results: SRBD (apnea-hypopnea index [AHI] > 15 events/h) was diagnosed in 445 (53%) subjects, 167 (37%) of them with AHI > 30. Minimal daytime sleepiness was found in the group; 9.2% of the population had an Epworth Sleepiness Scale score > 10. No signifcant association was found between AHI, nocturnal hypoxemia, and cognitive scores. Comparison of mild vs severe cases showed a trend toward lower cognitive scores with AHI > 30, affecting delayed recall and Stroop test. Conclusions: The impact of undiagnosed SRBD on cognitive function appeared quite limited in a generally older healthy population, and only slightly affected severe cases. The implication of undiagnosed SRBD on the cognitive impairment in elderly subjects remains hypothetical and needs to be prospectively studied. Clinical Trial Information: Autonomic Nervous System Activity, Aging and Sleep Apnea/Hypopnea (SYNAPSE); Registration #NCT 00766584 (This study is ongoing, but not recruiting participants.); URL - http://clinicaltrials.gov/ct2/show/NCT00766584?term=NCT+00766584&rank=1.