Obstructive sleep apnea
Sleep-disordered breathing refers to recurring arousals from sleep and intermittent reduced blood oxygen levels (hypoxia). This condition affects a sizeable fraction of elderly Americans. Several adverse health outcomes, including cardiovascular disease, hypertension, and diabetes, may arise from sleep-disordered breathing. A team of researchers sought to determine if objectively measured sleep-disordered breathing predicted increased risk of mild cognitive impairment or dementia in older women. The Study of Osteoporotic Fractures included 298 women with an average age of 82 years and without prevalent dementia. In their residences, the women wore a polysomnography device for one night to measure sleep interruptions. One hundred five of the women met the criterion for sleep-disordered breathing, namely 15 or more apnea-hypopnea interruptions per hour while sleeping.
Over an average follow-up of 4.7 years, 107 of the women developed mild cognitive impairment or dementia. After adjusting for sociodemographic and health factors, women with sleep-disordered breathing had 71 percent higher risk of developing mild cognitive impairment or dementia than women without sleep-disordered breathing during follow-up. Furthermore, women in the highest one-third of total sleep time in disordered breathing had a 104 percent higher risk of developing mild cognitive impairment or dementia than women in the lowest one-third of total sleep time in disordered breathing. Measures of sleep fragmentation or sleep duration did not predict cognitive impairment. Reduced oxygen supply to the brain might explain the connection between sleep-disordered breathing and subsequent cognitive impairment.
Researchers at the University of South Florida conducted a systematic review and meta-analysis of 27 longitudinal studies that evaluated links between sleep disorders and risk of cognitive problems. Sleep problems included short and long sleep duration, poor sleep quality, circadian rhythm abnormality, insomnia, and obstructive sleep apnea. Of these sleep problems, obstructive sleep apnea predicted the highest risk of subsequent cognitive decline or Alzheimer’s disease. Individuals with sleep problems had 55, 65, and 278 percent higher risks of Alzheimer’s disease, cognitive impairment, and pre-clinical Alzheimer’s disease, respectively, compared to individuals without sleep problems. If sleep problems cause Alzheimer’s disease, about 15 percent of Alzheimer’s disease cases could theoretically be prevented by eliminating sleep problems.
A subsequent systematic review and meta-analysis of 18 longitudinal studies focused on sleep disturbances and Alzheimer’s disease and other types of dementia. When different types of sleep disturbances (insomnia, sleep disordered breathing, and other types) were combined, individuals with a sleep disturbance had significant 19, 49, and 47 percent higher risks of developing all-cause dementia, Alzheimer’s disease, and vascular dementia, respectively, compared to individuals without a sleep disturbance. Individuals with sleep disordered breathing and other types of sleep disturbances (excluding insomnia) had significant 18 and 19 percent higher risks of all-cause dementia and 20 and 76 percent higher risks of Alzheimer’s disease, compared to individuals without such disturbances. Among different types of sleep disturbances, only sleep disordered breathing was significantly related to risk of vascular dementia.
Chinese researchers conducted an updated systematic review and meta-analysis of 51 longitudinal studies relating sleep disorders and cognitive decline and dementia. Sleep disorders with moderate to high levels of evidence included insomnia, fragmentation, daytime dysfunction, prolonged latency (time to fall asleep), rapid eye movement sleep disorder, and excessive time in bed. All these disorders predicted increased risk of all-cause cognitive problems. Insomnia predicted 27 percent higher risk of cognitive disorders including dementia, Alzheimer’s disease, and cognitive decline. Both low and high sleep duration predicted increased risk of dementia or cognitive decline (83 and 41 percent, respectively) compared to 8 hours of nightly sleep.
Thus, interventions that successfully treat sleep problems might reduce your risk of Alzheimer’s disease and other types of dementia. Plus, you'll feel better if you get enough restful sleep. If you think you might have a sleep disorder, seek medical attention.