Sleep-disordered breathing and cognition in older women

OBJECTIVES: To investigate the association between objectively measured sleep-disordered breathing (SDB) and cognitive impairment in community-dwelling older women and to determine whether the apolipoprotein E (APOE) epsilon 4 allele modifies this association. DESIGN: Cross-sectional. SETTINGS: Participants' homes and two sites of the Study of Osteoporotic Fractures (SOF). PARTICIPANTS: Four hundred forty-eight women with a mean age +/- standard deviation (SD) of 82.8 +/- 3.4. MEASUREMENTS: Participants completed the Mini-Mental State Examination (MMSE), Trail Making Test Part B (Trails B), and polysomnography (PSG). SDB indices were the apnea-hypopnea index (AHI), the central apnea index (CAI), and oxygen saturation (SaO(2)) nadir less than 80%. APOE epsilon 4 was determined for a subset of 242 women. Cognitive impairment was defined as 1.5 SDs or more from the sample mean on either cognitive test (MMSE or Trails B). RESULTS:All SDB indices were associated with cognitive impairment according to the MMSE (AHI (per SD, odds ratio (OR)=1.4, 95% confidence interval (CI)=1.03-1.9), AHI of >= 30 (OR=3.4, 95% CI=1.4-8.1), SaO(2) nadir < 80% (OR=2.7, 95% CI=1.1-6.6), and CAI (per SD, OR=1.4, 95% CI=1.1-1.7)). Weaker, nonsignificant associations emerged between SDB and Trails B. In women who completed genotyping, each SD increase in AHI was associated with 70% greater odds of cognitive impairment according to the MMSE (OR=1.7, 95% CI=1.2-2.6). Women with the epsilon 4 allele had a nearly five times greater odds of impairment (per SD, OR=4.6, 95% CI-1.0-20.7); the association was smaller and nonsignificant in women without the epsilon 4 allele (per SD, OR=1.5, 95% CI-0.9-2.4; P for interaction=.08). CONCLUSION: SDB is an important risk factor for cognitive impairment in older women, especially those with the APOE epsilon 4 allele. Mechanisms linking these disorders need to be identified.