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14-08-2011 | Psychology | Article

Sleep-disordered breathing linked to cognitive impairment in elderly women


Free abstract

MedWire News: Elderly women with sleep-disordered breathing (SDB) are at increased risk for cognitive impairment, suggest study results published in JAMA.

"SDB, a disorder characterized by recurrent arousals from sleep and intermittent hypoxemia, is common among older adults and affects up to 60% of elderly populations," explain Kristine Yaffe (University of California, San Francisco, US) and team.

They add: "Cross-sectional studies have linked SDB to poor cognition; however, it remains unclear whether SDB precedes cognitive impairment in older adults."

To investigate, the team studied data on 298 women, aged an average of 82.3 at enrolment, who participated in the Study of Osteoporotic Fractures.

All of the women, who were free of dementia at baseline, underwent overnight polysomnography between 2002 and 2004 to identify all those with SDB, defined as apnea-hypopnea index of at least 15 events per hour.

The participants' cognitive status was assessed at baseline and around 5 years later using a comprehensive battery of neuropsychological tests, including the Mini-Mental State Examination, a modified version of Trails B test, the California Verbal Learning Test, and the Questionnaire on Cognitive Decline in the Elderly.

At baseline, 35.2% of the women met criteria for SDB, and after 5 years, 35.9% had developed mild cognitive impairment or dementia.

The researchers found that 44.8% of women with SDB at baseline developed mild cognitive impairment or dementia after 5 years, compared with 31.1% of those without SDB at baseline.

After accounting for age, race, body mass index, education level, smoking status, presence of diabetes, presence of hypertension, medication use, and baseline cognitive scores, the team found that SDB was associated with a 1.85-fold increased risk for mild cognitive impairment or dementia among the women.

Further analysis showed that an oxygen desaturation index of more than 15 events per hour and more than 7% of total sleep time in apnea or hypopnea (both measures of hypoxia) were each associated with an increased risk for mild cognitive impairment or dementia, at odds ratios of 1.67 and 1.79, respectively.

Yaffe and team conclude: "The increased risk for cognitive impairment associated with sleep-disordered breathing opens a new avenue for additional research on the risk for development of mild cognitive impairment or dementia and exploration of preventive strategies that target sleep quality including sleep-disordered breathing."

By Mark Cowen

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